NCERT Solutions Class 6 Science Chapter 8 a Journey Through States of Water

F R E E S T U D Y M AT E R I A L F O R E V E R Y S T U D E N T

CLASS 6 · SCIENCE

NCERT Solutions

Chapter 8: A Journey through
States of Water

NCERT Textbook — Curiosity

BOOK PAGES SECTIONS QUESTIONS MEDIUM

143 – 162 25 71 English

Solutions, notes, sample papers & more at 70 pages

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

CLASS 6 · SCIENCE · CURIOSITY

NCERT Solutions — Chapter 8: A Journey through
States of Water
Complete NCERT Solutions for Class 6 Science Chapter 8 A Journey through States of Water from the NCERT
textbook Curiosity. Every question of the chapter is answered — Activities 8.1 to 8.11, the Let us draw and
More to do! boxes, all the in-text questions from pages 143 to 159, the ten questions of Let us enhance our
learning and the Learning further tasks. Melting, boiling, evaporation, condensation, the cooling effect and
the water cycle are explained with labelled diagrams, and every temperature is given with its unit °C.

TEXTBOOK BOOK PAGES

Curiosity (Class 6) 143 – 162

SECTIONS QUESTIONS

25 71

MEDIUM

English

In-text Questions — Page 143
Chapter opening — Aavi and Thirav look at the ice in their shikanji

Q1 Aavi has a counterview to Thirav. What do you think? Why?

Aavi is right. Ice and water are not two different substances — they are the same substance
in two different states.
Thirav's reason was that ice feels hard and can be held in the hand, while water cannot. That is a
real difference, but it is a difference of state, not of substance.

WHAT THIRAV NOTICED WHAT IT ACTUALLY SHOWS

Ice is hard and keeps its shape In the solid state the particles are locked in fixed places

Water cannot be held in the hand In the liquid state the particles can slide over one another, so water flows away

Same substance? Yes — nothing was added or removed, only heat

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Why we can be sure: the change works both ways. Keep water in a freezer and you
get ice; take the ice out and it melts back into exactly the same water. If ice were a
different substance, melting it would not give the water back. Also, the ice cube in
the shikanji does not make the drink more or less than it was — it simply melts into
it.

Check it yourself: Weigh a closed bottle with 100 g of water. Freeze it and weigh
again. The reading does not change — the ice is that very same water.

Q2 Do you think Thirav is right? How can you find out?

No, Thirav is not right. He thinks that when water is kept in a freezer, something gets added to it
and that is why ice is formed. Nothing is added — the water only loses heat and freezes.
How to find out — a simple test you can do at home:

1. Take a small bottle and fill it with drinking water. Mark the level and note the mass on a
kitchen balance.
2. Close the lid tightly and keep the bottle in the freezer for a few hours, until the water
becomes ice.
3. Take it out and weigh it again — the mass is the same. Nothing has entered the closed
bottle.
4. Leave the bottle on the table. The ice melts back into water, and the water is as clear and
tasteless as before.

Why this settles the question: if something had been added inside the freezer, (a)
the mass would have increased, and (b) the melted water would be different in some
way — cloudy, salty, or larger in amount. Neither happens. The only thing that
changed was the temperature: the water was cooled to 0 °C and below, so it froze.

Did you know? Water is unusual — it expands a little on freezing. That is why a full
bottle of water sometimes cracks or bulges in the freezer. The amount of water is
still the same; only the space it takes up has increased.

Activity 8.1: Let us observe — Page 144

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Putting an ice cube in a cup

ACTIVITY

Q1 Put an ice cube in a cup, leave it on the table and observe. What can you conclude
from the observations?

Observation: the ice cube slowly becomes smaller, loses its sharp edges, and after some time
only water is left in the cup. No new material appears and nothing is left over.
Conclusion:

Ice changes into water on its own when it is kept in a warm room. This change is called
melting.
The change happens because the ice takes heat from the room air and from the cup. Ice
melts at 0 °C, and a room is much warmer than that.
Since ice turns wholly into water and nothing else, ice and water must be forms of one and
the same substance.

Why it happens: in ice the particles are held in fixed places and can only vibrate.
Heat from the room makes them vibrate harder, until they break out of their fixed
places and begin to slide over one another — the ice becomes water.

Try This: Put one ice cube in a cup on the table and an identical cube in a cup inside
a cupboard. The cube on the open table melts sooner, because it gets heat faster. Do
not keep one in the sun and one in shade for this test — change only one thing at a
time.

Q2 Does this mean that ice and water are the same substance?

Yes. In the words of the textbook — ice and water are the two forms of the same substance. These
forms are also called states.
The two states behave very differently, and the book points out two of these differences:

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Class 6 Science Chapter 8 A Journey through States of Water
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BEHAVIOUR WATER (LIQUID) ICE (SOLID)

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Does it flow?
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Yes, water flows
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No, ice does not flow

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Does it splash?
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Yes, water splashes No, ice does not splash

Can you hold it in your hand? No Yes

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Does it keep its own shape?
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No, it takes the shape of the vessel Yes ag
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Why the behaviour differs although the substance is one: it is the arrangement
and freedom of the particles that differs, not the substance. Locked particles give a
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hard solid; loosely packed, sliding particles give a flowing liquid.
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In-text Questions — Page 144
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8.1 Investigating Water's Disappearing Act

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Q1 Have you ever noticed water in the puddles disappearing? Where does it go?
Discuss with your friends.

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Yes. Puddles that were full of water in the morning are small or completely dry by the evening.

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The water leaves the puddle by two routes:

a g It seeps into the ground. Soil, sand and mud have tiny spaces between their grains, and

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water sinks into them.
omsurface of the puddle slowly changes into water
It evaporates into the air. Water at cthe
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vapour, which mixes with the air

How you can tell that both are happening: a puddle on loose soil vanishes very

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fast — mostly seeping. A puddle on a cemented floor or a stone slab also dries up,

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and there the water cannot seep anywhere, so it must have evaporated. In the
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Tip for the discussion: ask your friends which puddle disappears faster — the one
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in the sun or the one in the shade of a tree. If seeping were the only reason, the
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shade should make no difference. It does make a difference, which shows that
evaporation is taking place.
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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Q2 Where else have you seen water disappearing? Can you think of a possible reason
why this happens?

Water disappears in dozens of everyday situations:

Wet clothes on a line dry up.
A mopped floor becomes dry in a few minutes.
Sweat on our skin dries after we sit in front of a fan.
Washed utensils and the wet slab of the kitchen dry by themselves.
Water sprinkled on a hot tawa vanishes almost at once.
Wet hair dries; a wet handkerchief dries in the pocket.
Water in an open glass left overnight is a little less in the morning.
Sea water in the shallow pans of a salt farm dries up and leaves salt behind.

The possible reason: in every one of these cases the water is not lost. It changes
into water vapour, a gas, and mixes with the air. Because water vapour is invisible, it
looks as if the water has disappeared. This process is called evaporation.

Did you know? Nothing in these examples is being heated to 100 °C. Evaporation
does not need boiling — it goes on quietly at room temperature, day and night.

Q3 You might have observed that after washing the utensils, water left on the surface
of the utensils, dries up after some time. Does the reason you thought earlier to
explain water disappearance apply in this case also?

Only partly. Of the two reasons given for the puddle, only one can work here.

REASON PUDDLE IN THE WATER ON A STEEL UTENSIL
PLAYGROUND

Seeping into the Possible — soil has spaces between its Not possible — steel is smooth and has no
surface grains such spaces

Evaporation into the Possible Possible — and this is what actually
air happens

So the "soil absorbed it" explanation does not apply to a steel plate or a steel katori. The water
there must be leaving by evaporation.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Why this example is so useful: it is a case in which one of the two possible causes
has been ruled out by the nature of the surface itself. Testing an idea in a
situation where only one cause can operate is a neat way of separating two mixed-
up causes — exactly what a scientist does.

Q4 Aavi wonders if water has seeped through the surface of the utensils. Thirav thinks
that water does not seep through the surface of the utensils. Design an activity to
investigate whose idea is correct.

The activity must be able to show seeping if it happens. So we must be able to look at the other
side of the surface while the water is disappearing.
Design:

1. Take a clean, dry steel plate and wipe its lower surface completely dry.
2. Put a tablespoon of water in the middle of the upper surface.
3. Rest the plate on two dry sticks or on the rims of two glasses, so that the lower surface is
open to view. Keep a dry sheet of paper underneath.
4. Every 10 minutes, look at the lower surface and at the paper. Also see how much water is left
on top.
5. Continue until the water on top has completely disappeared.

How to read the result:

If drops appear on the lower surface or the paper below gets wet → water is seeping (Aavi's
idea).
If the lower surface and the paper stay perfectly dry while the water on top vanishes →
water is not seeping (Thirav's idea), and it must have gone into the air.

What actually happens: the paper stays dry, so Thirav is right. This is precisely
Activity 8.2 in your book.

Tip: Use a fair test — keep a second, identical plate with the same amount of water
covered by an upturned bowl. Much less water disappears from the covered one,
which shows the water is escaping into the air, not through the steel.

Activity 8.2: Let us investigate — Pages 144 and 145

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

A tablespoon of water on a steel plate (Fig. 8.1)

ACTIVITY

Q1 What do you infer? Is this activity enough to come to the conclusion that water
does not seep through a steel plate?

Inference: the water on the steel plate slowly becomes a smaller and smaller patch and finally
disappears completely, while the underside of the plate remains perfectly dry the whole
time. So the water did not pass through the steel.
Is the activity enough? Yes, for this particular question — and here is why it is a good test:

Steel has no pores. Anything that seeped through would have to appear on the other side,
and we watched that side at regular intervals.
Nothing was placed below to soak up water, so a leak could not have been hidden.

But be careful about what you conclude: the activity proves that water does not
seep through steel. It does not, by itself, prove that evaporation is the reason for
the disappearance — it only removes the other possibility. To be fully sure we should
also repeat it with a covered plate, where the vapour cannot escape. Much less
water disappears then, and that is what pins the disappearance on evaporation.

Tip: Put the same amount of water on a dry earthen saucer as well. There the
underside does become damp, because clay is porous. Comparing the two makes
the role of the surface very clear.

Q2 If water does not seep through the steel plate. Then, where has the water gone?

It has gone into the air — changed into the gaseous state of water, which is called water
vapour.

Liquid water + heat from the room → water vapour (invisible gas)

This change is called evaporation.

Three facts worth remembering about water vapour:

It is invisible — that is why the water seems to vanish.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

It is the third state of water, along with ice (solid) and water (liquid).
It is always present in the air around us, even in a closed room.

Why the water leaves at ordinary room temperature: the particles of water are
always moving, some faster than others. The fastest particles at the surface can
escape into the air. This goes on continuously, at every temperature — it does not
wait for the water to reach 100 °C.

In-text Questions — Page 145
8.1 Investigating Water's Disappearing Act — evaporation

DO YOU KNOW?

Q1 While making dosa, we sprinkle some water on the hot pan and it disappears.
Where does it go?

The water changes into steam and goes into the air. As the book puts it — the water which is
sprinkled on the hot pan gets converted into steam. Steam is actually water vapour, some part of
which converts into water droplets.
Step by step:

1. The tawa is very hot — far above 100 °C.
2. The moment the drops touch it they take in a great deal of heat and change into vapour
almost at once, with a hissing sound.
3. Just above the tawa the vapour meets cooler air, and part of it turns back into tiny droplets.
This is the white cloud you see rising.
4. Higher up these droplets evaporate again and the vapour mixes with the air in the kitchen.

Do you know? Water vapour is actually invisible but the presence of tiny droplets of
water in the steam makes it visible. So the white plume you see is not vapour at all — it
is a mist of very small water droplets, which is already condensation happening in
front of your eyes.

Why the cook does it: sprinkling water tells the cook whether the tawa is hot
enough — if the drops skitter and vanish instantly, the tawa is ready — and the
vapour also carries away some heat, cooling the tawa a little so the dosa batter
spreads evenly instead of sticking.

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Class 6 Science Chapter 8 A Journey through States of Water
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The process of evaporation takes place continuously, even at room temperature.
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Q2

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Can you think of other examples of evaporation?

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The book gives three — drying of wet clothes, a mopped floor drying, and sweat on our

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body drying. Here are many more from an Indian home:
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WHERE YOU SEE IT
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Clothes on the line, a wet towel on a hook
a Water from the cloth

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Wet floor after mopping, a washed verandah Water from the floor

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Sweat drying under a fan Water from the skin

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a g Washed steel plates left on the rack Water on the metal

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Papads, badis, mango slices and red chillies drying on the Water inside the food

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terrace

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Water level in an open bucket or a birdbath falling Water from the open surface

Wet hair drying after a bath Water from the hair

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Salt pans of Gujarat and Tamil Nadu Sea water — the salt is left behind

coinma matka going down over a week l a
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Water Water seeping

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evaporating

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The common thread: in every case a liquid surface is open to the air and the
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temperature is ordinary. No flame,
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the fastest particles from the surface.

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(iii) Both of these.
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Seeping (percolation):
to become groundwater.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Evaporation: water at the open surface of the puddle changes into vapour and mixes with
the air. The Sun heating the ground makes this fast.

Why we cannot pick only one: Activity 8.2 showed that water evaporates even from
a surface it cannot seep through, so evaporation is certainly happening in the
playground too. At the same time, everyone has seen water sink into dry soil, so
seeping is happening as well. When two causes can both operate, the honest answer
is that both are at work — and their share differs from place to place. On a
cemented ground only evaporation is possible; on loose sandy ground seeping
does most of the work.

Check it yourself: After rain, mark the edge of one puddle on soil and one on a
cemented floor with chalk. Note how long each takes to dry. The soil puddle usually
goes first, because it has two exits instead of one.

Q4 Hand sanitiser disappears as you rub it on your hands. What happens to it?

The sanitiser evaporates — it changes from the liquid state into vapour and mixes with the air.
It is not absorbed by the skin and it is not "used up".
Two things make it disappear so quickly:

Sanitiser is mostly alcohol (spirit), and alcohol evaporates much faster than water at the
same temperature.
Rubbing spreads it into a very thin film over both palms and fingers, so the exposed area
becomes large — and a larger exposed area always means faster evaporation (Activity 8.7).

Why your hands feel cold: to change into vapour, the liquid needs heat, and it takes
that heat from your skin. Your palm loses heat and feels cool. This is the same
cooling effect that makes a matka keep water cold and makes sweating cool our
body — you will meet it again in Section 8.6.

Try This: Put one drop of sanitiser on the back of one hand and one drop of water
on the other. Blow gently on both. The sanitiser goes first and feels colder. Different
liquids evaporate at different rates.

Let us draw — Page 145

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Water sprinkled on a hot pan

LET US DRAW

Q1 Draw a detailed sketch (with labels and caption) about what happens to the water.

Your sketch must show three things: the hot tawa with the water drops, the vapour rising from
them, and the visible white steam formed when part of that vapour turns back into tiny
droplets. Label each one and add a caption.

What happens to water sprinkled on a hot pan
Steam — vapour + tiny droplets (visible white cloud)

Water vapour rising
Water drops (liquid) (invisible)

Hot tawa (far above 100 °C)

Water sprinkled on a hot tawa takes heat, evaporates into invisible water vapour, and part of that
vapour immediately cools and turns into tiny droplets — the white steam we can see.

What your labels should say:

Hot tawa — supplies the heat.
Water drops — the liquid state.
Water vapour — the gaseous state, invisible.
Steam — vapour together with tiny droplets, and therefore visible.

Sample caption: "Water sprinkled on a hot pan takes heat from the pan, changes
into invisible water vapour (evaporation), and a part of this vapour cools in the air
and turns back into tiny droplets, which we see as white steam."

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Activity 8.3: Let us experiment — Pages 146 and 147
8.2 Another Mystery — cold water and ice cubes in a glass tumbler

ACTIVITY

Q1 Take cold water in a glass tumbler, add a few ice cubes, leave it undisturbed for five
minutes and observe. Record your observations and the questions that arise in your
mind in Table 8.1.

I OBSERVE I WONDER

Table 8.1, page 146 — Record the observations and questions (blank, as printed).

Here is a completed Table 8.1. Write your own observations in the same way — one column for
what you see, one for what you wonder.

I OBSERVE I WONDER

Tiny water droplets appear all over the outer surface of the Where has this water come from, when I poured
tumbler. water only inside the tumbler?

The small droplets slowly join and become bigger drops, Why do the small drops join together?
which then trickle down.

The outer surface feels cold and wet when I touch it. Is the glass leaking? Or is the coldness itself
making the water appear?

A ring of water collects on the table below the tumbler. Will the water level inside go down by that
much?

The ice cubes become smaller and finally melt. Does the melting of ice have anything to do with
the drops outside?

The same thing happens with a metal container, but not with So is a cold surface necessary for the drops to
a tumbler of room-temperature water. appear?

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Why the book asks you to write questions too: in science, a good question is as
valuable as a good observation. The last row above is the question that finally solves
the mystery — it compares a cold tumbler with a warm one and points straight at
the real cause.

Q2 Suggest possible reasons explaining the appearance of water droplets on the outer
surface of the glass tumbler. Discuss with your friends. Write down the possible
reasons in Fig. 8.3.

May be ice has come
out of the glass
tumbler and melted.

Fig. 8.3, page 147 — redrawn sketch: write your own possible reasons in the three empty
bubbles.

Write down every reason that seems possible, even if you later find it wrong. That is how the
four children in Fig. 8.3 and Fig. 8.4 work.

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Class 6 Science Chapter 8 A Journey through States of Water
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POSSIBLE REASON HOW WE CAN TEST IT VERDICT

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Ice came out of the tumbler and melted Watch the rim carefully; the ice cubes are

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on the outside.
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clearly inside all the time.

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aWater Mark the water level with a marker and Wrong — the level
of the glass. check it after 30 minutes. does not fall

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Water splashed out while the ice was
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Pour gently, wipe the tumbler dry, and then Wrong — drops ag
being dropped in.
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a Wipe it completely dry before starting. Wrong — drops

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washing. still appear

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Water vapour present in the air Keep a second tumbler with water at room
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the temperature beside it. No drops appear on

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water. that one.

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Why the last reason wins: it is the only one that explains all the observations at
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once — why the drops appear only on a cold surface, why they appear on metal as
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well as glass, why the level inside does not fall, and why more drops appear on a
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humid day than on a dry one.

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Tip: When you write reasons in Fig. 8.3, write them as sentences that can be

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In-text Questions — Pages 147.and g l a
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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

8.2 Another Mystery — the chain of reasoning and condensation

Q1 Aavi and Thirav argued with a chain of reasons. What do you think about the
possible reasons mentioned in Fig. 8.4?

I think that some of the No, it cannot seep out.
water may have seeped The level of water in the
out of the glass tumbler. glass tumbler has not
decreased.

It might have decreased, With a tall and narrow
but may not be significant bottle, even a slight change
enough to be seen. in the level of water is
noticeable.

We can take water at room
temperature in another tumbler
and find out whether any
water seeps out.

Fig. 8.4, page 147 — redrawn sketch of the chain of reasoning between Aavi and Thirav.

Fig. 8.4 is a fine example of how scientific argument actually works — each statement is
answered by a check, not by shouting.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

STEP IN WHAT IT SAYS IS IT A GOOD MOVE?
THE CHAIN

1 "Some of the water may have seeped out of A fair starting guess — it can be tested.
the glass tumbler."

2 "No, it cannot seep out. The level of water in Good — this brings evidence against the guess.
the tumbler has not decreased."

3 "It might have decreased, but may not be Honest and important — it points out a
significant enough to be seen." weakness in the measurement, not in
the idea.

4 "With a tall and narrow bottle, even a slight Excellent — it improves the method so that a
change in the level of water is noticeable." small change would show up.

5 "We can take water at room temperature in Best of all — a control. If glass leaked, the
another tumbler and find out whether any warm tumbler would leak too.
water seeps out."

What I think: every step is reasonable, and none of them is a personal attack. The
children do not decide the answer by voting; they keep asking "how can we find
out?" That is why the chain ends with a well-designed experiment. Step 5 is the key
idea, because the room-temperature tumbler stays dry — proving that the glass
does not leak and that the coldness is what matters.

Tip: Notice that a "wrong" idea was still useful. Ruling out seeping is what left
condensation as the only surviving explanation.

Q2 Where else have you seen water droplets like this? You might have seen dew drops
on plants. Why do we see dew drops more in the morning?

Other places where the same droplets appear:

On a bottle of chilled water taken out of the refrigerator.
On the outside of a cold-drink bottle or a steel glass of lassi in summer.
On the inside of the windowpanes and the car windscreen on a winter morning.
On the mirror and tiles of the bathroom after a hot bath.
On spectacles when you come indoors from the cold, or when you breathe out with a mask
on.
On the inner side of the lid of a cooking pot.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

As mist on a cold steel spoon held above a cup of hot tea.

Why dew is seen more in the morning:

1. Through the night the leaves, grass and other objects lose heat to the open sky and become
colder than the air around them.
2. The air near them holds water vapour.
3. When this moist air touches the cold leaf, the vapour condenses into tiny drops — dew.
4. The coldest hour is just before and around sunrise, so the dew is thickest then. As the Sun
rises and warms everything, the drops evaporate and by mid-morning the grass is dry.

Why it is the same story as the tumbler: in both cases moist air meets a surface
colder than itself. The tumbler is made cold by the ice; the leaf is made cold by
losing heat all night. The vapour has nowhere to stay as a gas, so it turns liquid.

Did you know? Dew is heaviest on clear, still, cool nights. On a cloudy night the
clouds send heat back to the ground, the leaves do not cool enough, and there is
little dew in the morning.

Q3 When we boil the water in a half-filled utensil and cover it with a steel plate, some
water drops accumulate on the inner side of the steel plate. Where do these water
drops come from? What do you think?

Those drops come from the water vapour rising from the boiling water. They are not
splashes, and no water has come from outside.

Boiling water at 100 °C → water vapour rises

Vapour meets the cooler steel plate

Vapour loses heat → turns into liquid → drops on the inner side of the plate

Evidence that this is right:

The drops are on the inner (lower) side of the plate — the side facing the vapour — not on
top.
They appear even if the plate was wiped bone dry before covering.
If you use a cold plate, drops form faster and in larger numbers; a plate already heated over
the flame collects almost none.
Water in the pot slowly becomes less — that lost water is what you are collecting on the
plate.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Why the plate has to be cooler: condensation needs the vapour to lose heat. A
plate at room temperature is far below 100 °C, so vapour touching it cools instantly
and turns back into water. If the plate were as hot as the steam, no drops would
form.

Everyday use: This is exactly how an idli steamer, a bhapa dish and a rice cooker
work — and it is the principle behind distillation, by which clean water is obtained
from salty or muddy water.

Q4 When the water vapour present in the air comes in contact with a cold surface, it
forms water droplets. Could the water appearing on the outer surface of the glass
tumbler in Activity 8.3 also be due to condensation of water vapour present in the
air?

Yes. That is exactly what it is. The process is called condensation — the process of conversion of
water vapour into its liquid state.
Why the tumbler is a perfect setting for it:

1. The ice keeps the water inside at about 0 °C, so the wall of the tumbler becomes very cold.
2. The air of the room always contains water vapour — that is its humidity.
3. Air touching the cold glass is chilled. Chilled air cannot hold as much vapour as warm air.
4. The extra vapour condenses on the glass as a film of tiny droplets, which merge into bigger
drops and run down.

How the chapter proves it beyond doubt: two checks are made. (a) In Activity 8.4
the whole set-up is weighed on a digital balance and the reading increases — water
has been added from the air, not lost from inside. (b) The water level inside is marked
with a permanent marker and it does not go down, so nothing has leaked out.
Together, these settle the matter.

Did you know? Condensation is the reverse of evaporation. Evaporation needs heat;
condensation gives heat out. That is why the steam of a pressure cooker can scald
you far more badly than boiling water at the same 100 °C.

Activity 8.4: Let us measure — Pages 148 and 149

Page 18 of 70

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Class 6 Science Chapter 8 A Journey through States of Water
a g l AglaSem · NCERT Solutions

Weighing the condensation experiment on a digital balance
co m
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m as
ACTIVITY

.co a g l
a s em what will happen to the mass of cold water kept on the digital weighing
gl
Predict
a
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balance. Will it increase or decrease or remain the same?

co m
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Prediction: the reading will increase.
g l as
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Think about what each of the three possible answers would mean:

co m
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IF THE READING… …IT WOULD MEAN

m as e
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m
decreases Water is leaking out of the tumbler and dripping away, or water is escaping as vapour

l a se
ag stays the same The water outside simply came from inside — nothing gained, nothing lost

m a s
increases Water has been added from outside — from the air

em
.co agl
a s
Because the tumbler is covered with a steel plate, no vapour can escape from inside; and

a gl water from the air on the cold outer wall, the total
because condensation keeps depositing
mass on the pan goes up — slowly at first and then steadily, for as long as the tumbler stays
cold.
co m
m .
m as e
.co
Why making a prediction first matters: writing down what you expect before the
a g l
s e m
reading changes turns the activity into a real test. If the mass had fallen, the seeping

agla idea would have survived. It did not fall — so the prediction based on condensation
m
was correct.

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co m
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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Q2 Observe the reading on the balance and record the weight after every five minutes
for 30 minutes in Table 8.2. Do your findings match with your predictions? Explain
your observations.

TIME MASS OF WATER

0 min

5 min

10 min

15 min

20 min

25 min

30 min

Table 8.2, page 149 — Measurement of mass in condensation experiment using a digital
weighing balance (blank, as printed).

Yes, the findings match the prediction — the mass increases. A typical set of readings looks
like this (your own values will differ with the size of your tumbler and the humidity of the day):

TIME MASS OF THE SET-UP GAIN SINCE THE START

0 min 254.0 g —

5 min 254.3 g 0.3 g

10 min 254.7 g 0.7 g

15 min 255.0 g 1.0 g

20 min 255.4 g 1.4 g

25 min 255.7 g 1.7 g

30 min 256.0 g 2.0 g

Explanation of the observations:

Page 20 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

The tumbler and plate are cold. Water vapour from the air touches this cold surface and
condenses into droplets on the outside.
That water was in the air before and is now on the balance pan — hence the reading rises.
The gain is roughly steady — about 0.3 to 0.4 g every five minutes — because condensation
continues as long as the surface stays cold.
Once the ice has melted and the tumbler warms up towards room temperature, the gain
slows down and finally stops.

Why the numbers are small: only a thin film of droplets forms, so the change is a
fraction of a gram — which is exactly why a digital balance is used. An ordinary
beam balance would show nothing at all, and you might wrongly conclude that
nothing had happened.

Tip: Do not lift the tumbler between readings, and do not breathe over it. Both
would spoil the measurement. Read the display without touching anything.

Q3 There is an increase in the reading on the digital weighing balance. Can we
conclude that water is not seeping through the wall of the tumbler? Can we also
conclude that the water collected outside the tumbler is only due to condensation?

To the first question — not conclusively. To the second question — no. The book itself says,
No, we cannot say that conclusively from Activity 8.4.
Why one experiment is not enough here:

The balance shows the mass of the whole set-up together — tumbler, water, ice, plate and
the drops outside. If a little water seeped out through the glass, it would still be sitting on
the pan and the total would not change because of it.
So the rise in mass proves that water has been gained from the air, but it cannot prove
that no water is also seeping out at the same time. Both could be going on together.

What the experiment does prove: water has definitely been added from outside
the system — condensation is certainly happening. That is a solid result. What it
leaves open is whether seeping is happening as well. A good scientist reports exactly
this much and no more.

Page 21 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Tip: This is a very useful habit — after every experiment ask, "what does my result
rule out, and what does it leave open?" Claiming more than your data allows is one
of the commonest mistakes in science.

Q4 What more can you do to show that water is not seeping from the glass tumbler?
How would you modify Activity 8.4 to find the answer? What do you observe, and
what can you conclude from this?

The modification given in the book: repeat Activity 8.4 after marking the water level on the
glass tumbler with a permanent marker or a strip of visible tape. Then watch the mark, not
the balance.
What you observe:

The water level inside does not go down — it stays exactly at the mark (in fact it rises very
slightly as the ice melts).
Meanwhile, more and more water collects on the outer surface of the tumbler.

Conclusion: water is not seeping out through the glass. The extra water on the outside is
coming from the air, and it is getting collected there because of condensation.

Why the marker settles it: the previous experiment weighed everything together
and so could not separate "gained from air" from "lost from inside". The mark looks
only at the water inside. If seeping were happening, the level would have to fall. It
does not fall — so seeping is ruled out.

Two further checks you can add: (1) use a tall, narrow bottle instead of a wide
tumbler, so that even a tiny loss of water would show as a big drop in level; (2) keep
an identical tumbler of room-temperature water beside it — it stays completely
dry outside, proving that it is the cold surface, not the glass, that produces the
drops.

More to do! — Page 149

Page 22 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Humidity data for your area

MORE TO DO!

Q1 The amount of water vapour in the air is also known as humidity. The daily
humidity data for your area is reported in the newspapers and other sources.
Compile the data for the year and study any patterns, if present.

How to do it:

1. Keep a notebook with three columns — Date, Maximum humidity (%), Minimum humidity
(%). Many newspapers print both; some print only one figure.
2. Note the value every day at the same time from the same source — the weather column of
the newspaper, the IMD website, or a school weather station.
3. At the end of every month, work out the monthly average and mark it as a point on a
graph: months along the bottom, humidity up the side. Join the points.
4. On the same sheet, mark the months of the monsoon in your region.

The pattern you are likely to find in most of India:

SEASON TYPICAL HUMIDITY WHAT YOU NOTICE

Peak summer (April–May, Low, often 20–40 % Clothes dry very fast; the matka cools
inland) water well

Monsoon (June–September) High, often 80–95 % Clothes smell damp and take a whole
day to dry

Winter (December–January) Moderate; high at dawn, low by Heavy dew and fog in the morning
afternoon

Why the daily figure changes so much: humidity is usually highest just before
sunrise and lowest in the afternoon. The air holds nearly the same amount of
vapour all day, but warm afternoon air can hold much more, so the air is further
from being full — and evaporation speeds up.

Tip: Coastal cities such as Chennai, Mumbai and Kochi stay humid for most of the
year, while Jaipur, Nagpur and Delhi swing between very dry summers and very
humid monsoons. Compare your graph with a friend's from another town.

Activity 8.5: Let us identify — Page 150

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Class 6 Science Chapter 8 A Journey through States of Water
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8.3 What are the Different States of Water? (Table 8.3)
co m
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m as
ACTIVITY

.co a g l
a s eman ice cube in one container and transfer it to another container of different
gl
Put
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shape. What changes do you notice in the shape of the ice cube?

co m
em . ag
g l as
No change at all. The ice cube keeps its own shape — it is still a cube, whichever container you
put it in. a
Put it in a round katori — it stays a cube.
co m
Tip it into a tall glass — it stays a cube.
em.
m l as
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Put it on a flat plate — it stays a cube.

em a
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The only change is that it slowly gets smaller and its corners become rounded, but that is

a gmelting, not the container acting on it.

om a s
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Why a solid keeps its shape: in ice the particles are packed in a fixed, regular
arrangement and are held tightlyein
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laa whole cannot change form. This is the defining
their positions, so the block gas
a
property of the solid state.

co m
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m l a se
Check it yourself: Try the same with a marble, a piece of chalk and a rubber. None
o
c takes the shape of its container either — all solidsagbehave this way.
of .them
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ase
agl
se m
com
Pour water from one container to another container of a different shape. Observe
g l a
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Q2

e m
as What happens to its shape?
how water behaves compared to the ice cube. Did you notice how water flows from

g l
one container to the other?
a
co m
m .
e
Water behaves in exactly the opposite way to ice.
m l as
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m takes the shape of the stream while pouring. a g
It flows smoothly and continuously from one vessel to the other — you can pour it, and it

l a se
ag
c
It takes the shape of the new container completely. In a round bowl it is round, in a square

m .
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box it is square, in a tall glass it is a tall column.

om la s
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It has a flat, level upper surface in every container.
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l a sestayed constant.
ag
shape changed; the volume

com
m .
m ase
.co


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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Why a liquid behaves like this: in water the particles are still close together —
which is why the volume does not change — but they are not locked in fixed places.
They can slide past one another. So the water can rearrange itself to fit any vessel,
and it can flow.

Tip: Note carefully — a liquid has a definite volume but no definite shape. A solid
has both. Getting this pair right answers most questions on states of matter.

Q3 Pour water on a clean surface and observe how it spreads. Record your
observations in Table 8.3.

PROPERTY ICE WATER WATER VAPOUR
(SOLID STATE) (LIQUID STATE) (GASEOUS STATE)

Shape

Ability to flow

Ability to spread

Table 8.3, page 150 — Compare different states of water (blank, as printed).

Observation: the water does not stay in a heap. It spreads out over the surface into a thin, flat
sheet, and keeps spreading until it is stopped by an edge or by a groove.
Notice also that the amount does not change — the same water simply covers a larger area in a
thinner layer. Water spreads while keeping its volume constant.
Here is Table 8.3 completed:

Page 25 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

PROPERTY ICE (SOLID STATE) WATER (LIQUID STATE) WATER VAPOUR
(GASEOUS STATE)

Shape Fixed — keeps its own No fixed shape — takes the No shape at all — fills the
shape in every container shape of the container whole container

Ability to flow Does not flow Flows easily Flows and moves freely in
every direction

Ability to Does not spread Spreads over a surface, Spreads out into the entire
spread volume staying the same available space

Why ice does not spread but water does: spreading needs the particles to move
past one another. In ice they cannot; in water they can.

Q4 When water gets converted into water vapour, how does this water vapour spread?
Compare this with the spreading behaviour of water.

Water vapour spreads out into the entire space available to it — in every direction, upwards
as well as sideways — until it is evenly mixed through the whole room or the whole container.

POINT OF WATER (LIQUID) WATER VAPOUR (GAS)
COMPARISON

Direction of spreading Sideways along a surface only; it cannot Every direction, including upwards
climb

How far it spreads Until stopped by an edge; it stays at the Until it has filled the whole vessel or
bottom of a vessel room

Volume Constant — 200 mL stays 200 mL Not fixed — it expands to whatever
volume it is given

Upper surface Has a flat, level surface Has no surface at all

Can you see it? Yes No — it is invisible

Why a gas spreads so completely: in water vapour the particles are very far apart
and move very fast, in all directions. There is almost nothing holding them together,
so they keep moving until they are spread evenly everywhere. This is why a gas has
neither a fixed shape nor a fixed volume.

Page 26 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Everyday proof: a wet floor stays wet only where the water is, but the smell of a
chapati on the tawa reaches the whole house within a minute. Gases spread; liquids
do not.

In-text Questions — Pages 150 and 151
8.3 What are the Different States of Water?

Q1 What are the differences in the properties of water in solid, liquid and gaseous
states?

The three states differ in shape, flow, spreading and volume — and all of these follow from
how the tiny particles are arranged.

Ice — solid state Water — liquid state Water vapour — gaseous state

Shape: fixed, its own Shape: of the container Shape: none
Flows: no Flows: yes Flows: yes
Spreads: no Spreads: yes, volume same Fills all the space

The same substance in three states. In ice the particles sit in a fixed, regular arrangement and can
only vibrate in place. In water they are still close together but can slide past one another. In water
vapour they are far apart and move freely, filling all the space available.

The differences, in the words of the chapter:

Ice (solid): retains its shape whatever the container. Does not flow and does not spread.
Water (liquid): flows and changes its shape. It has no fixed shape and takes the shape of
the container, but its volume remains constant. It also spreads, again keeping the volume
constant.
Water vapour (gas): spreads out in the entire available space. Gases do not possess a
fixed shape. Water vapour exists even at room temperature, though it is invisible to us, and it
is present in the air around us.

Page 27 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Why the particle picture explains everything: shape is fixed when particles are
locked (solid); volume is fixed when particles touch each other, whether locked or
sliding (solid and liquid); neither is fixed when particles are far apart and free (gas).

Q2 Look around and find some examples of solid substances. What are the other
examples of liquids you can think of? Think of five more examples. What are the
other examples of gases you can think of?

The book starts you off — solids: stones, wood, glass; liquids: milk, oil; gases: oxygen, carbon
dioxide. Here are plenty more from around you.

SOLIDS LIQUIDS GASES

Stone, brick, wood Milk Oxygen

Glass, steel, copper wire Mustard or coconut oil Carbon dioxide

Chalk, pencil, book Honey Nitrogen

Ice, sugar, salt Kerosene and petrol Water vapour

Plastic ruler, rubber, cloth Vinegar, lemon juice, tea LPG (cooking gas)

Candle wax, ghee in winter Ink, sanitiser, buttermilk Helium in a balloon; the air itself

Five more liquids, as the book asks: honey, kerosene, lemon juice, ink and buttermilk (chaas).

A caution worth remembering: the same substance can appear in more than one
state. Wax, oil and ghee are named in the chapter for exactly this reason — ghee
and coconut oil are liquid in summer and solid in winter, and wax is solid in the
candle but liquid in the pool near the flame. The state depends on the temperature,
not on the name of the substance.

Tip: When you list a gas, remember that most gases are invisible. Do not write
"smoke" or "steam" as gases — smoke contains solid particles and steam contains
liquid droplets.

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Class 6 Science Chapter 8 A Journey through States of Water
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co m
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Have you ever noticed that you can smell the food being cooked even without
e
Q3

m l as
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entering the kitchen? How does this smell reach us?

a g
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Yes. The smell reaches us because it travels through the air, as a gas.

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1. When food is heated, very tiny particles of the smelling substances in it escape from the

s
surface and become a gas — just as water
e m becomes water vapour.
g a in all directions.
2. These gas particles move very fast land
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3. Because a gas spreads out into the entire available space, they travel out of the kitchen,
along the passage and into every room.
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4. They reach our nostrils, and we recognise the smell of the tadka long before we see the food.

m l as
.co a g
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Why this example is placed here in the chapter: it is a direct proof of the gas

a gl property that the class has just learnt. In the book's own words — the smell of yummy
food from cooking spreads through the air and reaches our nostrils, even if we are not in

a s
com agl
the kitchen. Solids and liquids cannot do this; a spoonful of hot dal on the table stays
.
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where it is put, but its smell reaches everyone.
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. c om
corner of a room and stand still in the opposite corner. In half a minute the smell

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In-text Questions — Page 152
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8.4 How can we change the States of Water?

MORE TO KNOW!
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state, water?

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The state of water is changed by supplying heat or by taking heat away — nothing else is
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needed.

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a

com
m .
m ase
.co


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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Ice + heat → Water + heat → Water vapour

Water vapour − heat → Water − heat → Ice

To change ice quickly into water, supply heat fast. Practical ways:

Put the ice in a warm room or in sunlight instead of leaving it in the freezer.
Hold it in your palm, or pour warm water over it.
Put it in a metal (steel) bowl rather than a plastic one — metal carries heat to the ice faster.
Break the ice into small pieces or crush it. Small pieces have a much larger surface
touching the warm air, so they melt much faster than one big block.
Stir the ice in water — moving water keeps bringing fresh heat to the surface of the ice.

Why heat is what matters: ice melts at 0 °C. To melt it, we must bring it to that
temperature and then keep feeding it heat while it melts. Everything on the list
above is simply a way of delivering heat to the ice faster.

Did you know? While ice is melting, its temperature stays at 0 °C even though heat is
going in. All that heat is used up in breaking the particles out of their fixed places.
Only after the last bit of ice has melted does the water start getting warmer.

Q2 If we want to change water into ice, what should be done?

We must take heat away from the water — that is, cool it down to 0 °C and keep cooling it.
In the words of the book: It can be done by placing water in a cold environment, such as a freezer.
Water freezes and is converted into ice. If we take the ice out of the freezer, it melts and is converted
into water.

Page 30 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

CHANGE NAME OF THE WHAT MUST BE TEMPERATURE
PROCESS DONE

Solid → Melting Supply heat Ice melts at 0 °C
Liquid

Liquid → Freezing Remove heat Water freezes at 0 °C
Solid

Liquid → Evaporation (and Supply heat Evaporation at any temperature;
Gas boiling) boiling at 100 °C

Gas → Condensation Remove heat Whenever vapour meets a colder
Liquid surface

Why a freezer works: a freezer does not "make cold". It pumps heat out of the
space inside and throws it away at the back of the refrigerator — which is why the
back of a fridge feels warm. The water inside loses heat, its particles slow down and
lock into fixed places, and it becomes ice.

More to know! An Atmospheric Water Generator (AWG) uses the reverse idea. It
cools humid air so that the water vapour in it condenses, and collects that water for
drinking. It is the same process as the drops forming outside a tumbler of ice-cold
water — done on a large scale.

Q3 Can you think of any other example, besides water, that can change from solid to
liquid? How can we turn candle wax into liquid state? How can we change the liquid
wax back into solid state? What are the other liquids you have seen which get
converted into a solid?

Yes — a candle, which is made of wax, is the example the book gives. Many everyday
substances behave in the same way.
Turning candle wax into a liquid: light the candle, or hold a piece of wax in a spoon over a
flame. The wax takes in heat, melts, and a small pool of clear liquid wax collects around the
wick.
Turning liquid wax back into a solid: cool it. Blow out the flame and the molten wax hardens
in a minute; pour it into a cold spoon and it sets even faster. In the book's words — we should
cool the liquid wax to change it into a solid.
Other liquids you have seen turning into solids:

Page 31 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Coconut oil — it becomes white and solid in the winter months and clears again in summer.
The book asks about exactly this.
Ghee and butter — solid in winter, runny in May.
Vanaspati and dalda in a cold kitchen.
Molten jaggery or sugar syrup, which sets hard into chikki or a lollipop.
Melted chocolate setting again in the fridge.
Molten metal poured into a mould by a bell-maker, setting into a solid bell.
Water itself, of course, freezing into ice.

The general rule: the process of conversion of a solid into liquid state is called melting;
the process of conversion of liquid into solid state is called freezing. Each substance has
its own melting temperature — coconut oil sets at about 24 °C, so a cool night is
enough, while water needs 0 °C and iron needs well over 1500 °C.

Activity 8.6: Let us complete the diagram — Page 152
Fig. 8.5 Conversion of different states of water

ACTIVITY

Q1 Fill up the blank boxes in Fig. 8.5 marked as A, B, C and 1, 2, 3, 4 for conversion of
different states of water using the words given in the box. Two words have been
filled for you. [Liquid, Freezes, Evaporates, Gas, Condenses]

Liquid, Freezes, Evaporates, Gas, Condenses

1. Melts 2.

A. Solid B. C.

3. 4.

Fig. 8.5, page 152 — Conversion of different states of water. Two words are already filled
in, as in the book.

The completed diagram:

Page 32 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

melting — ice melts at 0 °C evaporation (boiling at 100 °C)
1. Melts 2. Evaporates

A. Solid B. Liquid C. Gas
(Ice) (Water) (Water vapour)

3. Freezes 4. Condenses
freezing — water freezes at 0 °C condensation — on cooling

Fig. 8.5 completed. The green arrows (going right) all need heat to be supplied; the blue arrows
(going left) all need heat to be removed.

BLANK ANSWER WHAT IT MEANS

A Solid (already filled — ice) Water in its solid state

B Liquid Water in its liquid state

C Gas Water vapour, the gaseous state

1 Melts (already filled) Solid → Liquid, on heating, at 0 °C

2 Evaporates Liquid → Gas, on heating

3 Freezes Liquid → Solid, on cooling, at 0 °C

4 Condenses Gas → Liquid, on cooling

How to place the words without guessing: box 1 Melts is given and it sits on the
arrow from A (Solid) to B, so B must be Liquid. Then the only remaining state word
is Gas for C. Arrow 2 goes from liquid to gas, so it is Evaporates; arrow 3 comes back
from liquid to solid, so it is Freezes; arrow 4 comes back from gas to liquid, so it is
Condenses.

Tip: Remember the pairs — melting and freezing are opposites (both at 0 °C for
water), and evaporation and condensation are opposites. In each pair, one takes
heat in and the other gives heat out.

In-text Questions — Page 153

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Class 6 Science Chapter 8 A Journey through States of Water
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8.5 How can Water be Evaporated Faster or Slower?
co m
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Observe your surroundings. What are the conditions that affect how fast water
a g
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Q1

a s
evaporates? What differences do you see in evaporation on a cold day versus a hot

a gl day? Discuss with your friends. The following words may help in your discussion—
fan, drying cloth, sweating, windy day, hot day, rainy day.

com
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as

a g l
Four conditions decide how fast water evaporates. Each of them can be seen in the words the
book suggests:

co m
CONDITION EVAPORATION IS FASTER WHAT YOU SEE AROUND YOU
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WHEN…

m a
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Temperature it is hotter On a hot day clothes dry by noon; in winter the same

a clothes stay damp till evening

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Movement of air moves faster A fan dries a mopped floor quickly; on a windy day

em
air

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the water is spread lover a larger
Exposed area
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A drying cloth spread wide on the line dries much
area sooner than one left bunched up

co m
Humidity
.
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the air is drier On a rainy day the air is already full of vapour, so

a s
com
clothes and floors dry very slowly

.
emday versus cold day: on a hot day the water particles already have more energy, so many agl
a s
Hot

agl more of them can escape from the surface each second. The puddle dries in an hour, sweat
se m
disappears from the skin at once and leaves us cooled, and the water in an open bucket goes

com
down noticeably. On a cold day, all of this happens, but far more slowly — evaporation never
g l a
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stops, it only slows down.

agl
Why all four conditions work in the same direction: evaporation is the escape of

m
the fastest particles from the surface. Heat gives them more speed; a large surface
. co
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gives more of them a door to escape from; moving air carries the escaped vapour

m as e
.co
away so the door does not get blocked; and dry air has more room to receive them.
a g l
se m
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a Tip: When you design an experiment on this, change only one of the four and keep
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the other three the same. That is exactly what Activities 8.7 and 8.8 do.
m a s
em . co agl
g l as
a
Activity 8.7: Let us investigate — Pages 153 and 154

co m
m .
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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Water in a bottle cap and water in a plate (Tables 8.4 and 8.5)

ACTIVITY

Q1 What conditions did we keep the same? What did we change in this investigation?
What did we measure?

These three questions are the backbone of every fair test.

QUESTION ANSWER FOR ACTIVITY 8.7

What did we The amount of water (same quantity in the cap and in the plate), the liquid used (water in both,
keep the same? or sanitiser in both), the place — both kept near each other, so the same temperature, the same
air movement and the same humidity, and the starting time.

What did we Only one thing — the exposed area of the water. It is small in the bottle cap and large in
change? the plate.

What did we The time taken for the water to evaporate completely in each case.
measure?

Why the two must be kept side by side: if one were kept on a sunny window sill
and the other in a cupboard, two things would have changed at once — area and
temperature — and we could never say which of them caused the difference.
Changing exactly one condition is what makes the test fair.

Tip: Measure the water with the same spoon or the same measuring cap for both.
"About the same" is not good enough when you are timing the difference.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Q2 Record the time taken for the water to completely evaporate in each case in Table
8.4. What can you conclude from this investigation?

EXPOSED AREA OF WATER TIME TAKEN FOR COMPLETE EVAPORATION

Less (bottle cap)

More (plate)

Table 8.4, page 154 — Findings of the investigation (blank, as printed).

Table 8.4, filled with typical readings for one teaspoon of water on a warm day (your own times
will differ):

EXPOSED AREA OF WATER TIME TAKEN FOR COMPLETE EVAPORATION

Less (bottle cap) About 3 hours

More (plate) About 35 minutes

Conclusion: water in the plate evaporates much faster than the same amount of water in the
bottle cap. In the words of the book — if you spread out water on a plate, its area exposed to air is
larger. Therefore, evaporation is faster.

Larger exposed area → more water particles at the surface → faster evaporation

Why area matters so much: particles can only escape from the surface of the
water, not from deep inside it. In the cap, a small circle of water faces the air; in the
plate, the same water is a wide thin film with many times that area. More surface
means more escape routes, so the same amount of water leaves in a fraction of the
time.

Where we use this every day: we spread wet clothes wide instead of leaving them
folded; we spread grain, papads and chillies in a thin layer on the terrace; tea is
poured into a saucer to cool it; and salt farmers spread sea water in wide shallow
pans rather than deep tanks.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Q3 What would happen if milk is taken instead of water in the above activity?

The same pattern would be seen — the milk in the plate would dry much sooner than the milk
in the bottle cap — but there would be some interesting differences.

Milk is mostly water, so the water in it evaporates in exactly the same way, and the exposed
area still decides the speed.
Milk would take a little longer than plain water, because the fat, protein and sugar in it form
a skin on the surface that slows the escape of water particles.
The milk would not disappear completely. When all the water has gone, a dry whitish-
yellow layer of solid milk residue is left behind — the fat, protein, milk sugar and minerals.
Left too long, that residue would smell sour, because milk spoils.

What this teaches: only the water in the milk evaporates. The solids dissolved and
suspended in it stay behind. This is the same principle that gives us khoya (mawa)
when milk is boiled down for hours, and salt when sea water dries in the salt pans.

Tip: If you actually try this, use a very small quantity and throw the residue away —
do not taste it.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Q4 Design an activity similar to Activity 8.7 to find out what are the other conditions
which can affect how fast water will evaporate. What would you change? What
would you keep the same? Use Table 8.5 to record the data.

Condition that is kept the same: ______________________

CONDITION THAT IS CHANGED TIME TAKEN FOR COMPLETE EVAPORATION
................................

Table 8.5, page 154 — Record the data of an investigation where one condition is
changed and other condition remains the same (blank, as printed).

Pick one condition, change only that, and keep everything else the same. Here are three good
designs.

DESIGN CONDITION CONDITIONS KEPT THE WHAT YOU FIND
CHANGED SAME

A. Air One saucer under a running Same saucers, same amount The saucer under the
movement fan, one in still air in the of water, same room fan dries much sooner
same room temperature, same humidity,
started together

B. One saucer on a sunny Same saucers, same water, The warmer saucer
Temperature window sill, one in the same still air dries much sooner
shade of the same room

C. Humidity One saucer in the open Same saucers, same water, The covered saucer
room, an identical one same place, same temperature hardly dries — the air
covered by an upturned trapped in the jar soon
glass jar becomes full of vapour

Table 8.5, filled in for Design A:

Page 38 of 70

as e
Class 6 Science Chapter 8 A Journey through States of Water
a g l AglaSem · NCERT Solutions

co m
m.
CONDITION THAT IS KEPT THE SAME: AMOUNT OF WATER, SIZE OF THE SAUCER, ROOM

m
TEMPERATURE, HUMIDITY
as e
.co a g l
s em
CONDITION THAT IS CHANGED
a
TIME TAKEN FOR COMPLETE EVAPORATION
l
g air (no fan)
aStill About 2 hours 30 minutes

co m
. ag
Moving air (fan at full speed) About 45 minutes

se m
l a
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Why moving air speeds evaporation up: the layer of air just above the water
quickly fills with vapour and then blocks further escape. A fan or a breeze keeps

co m
m.
sweeping that saturated layer away and brings fresh, drier air, so evaporation can

m
continue at full speed.
as e
.co a g l
a s em
a gl Check it yourself: Design C is the most surprising one and needs nothing but a
glass jar. It shows in the clearest possible way that humidity — the vapour already

m a s
.co agl
present in the air — is what finally stops evaporation.

se m
g l a
a
Activity 8.8: Let us explore — Pages 155 and 156
co m
Two bottle caps of water, one in sunlight and one in shade (Fig. 8.6)
m .
m ase
ACTIVITY
.co
DO YOU KNOW?

a g l
a s em
agl Q1 Place one cap in sunlight and keep the other in shade, observe them after every 15
minutes and record the time taken for the water to completely evaporate in each
se m
com
case. What conclusions can you draw from Activity 8.8 and other similar
g l a
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experiences?

ANSWER agl
Typical readings for equal amounts of water in two identical caps on a clear summer day:
co m
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WHERE THE CAP IS KEPT
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TIME FOR COMPLETE EVAPORATION
a
a s em In sunlight
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About 1 hour 15 minutes

a c
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In shade About 4 hours

m a s
Conclusions, in the words of the book:
e m . co agl
g l as
a
Water evaporates faster from the cap kept in sunlight compared to the cap kept in
shade.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

It is a common observation that clothes dry faster on a hot sunny day.
With the increase in the movement of air, water evaporates faster — clothes dry faster
on a windy day.
On a rainy day water evaporates slowly, because the air is already high in humidity.

Why sunlight makes such a large difference: sunlight warms both the water and
the cap. Warmer water means faster-moving particles, and a far greater number of
them can break away from the surface each second. Notice that the two caps were
identical and held the same amount of water, and were watched at the same 15-
minute intervals — so temperature was the only condition that differed.

Tip: Do not simply write "the sun dries it". Say which condition changed — the
temperature of the water — and that everything else was kept the same. That is
what turns an observation into a conclusion.

Q2 It is a common observation that clothes dry faster on a hot sunny day. Do clothes
dry faster or slower on a windy day?

Faster. Clothes dry more quickly on a windy day — often faster than on a still, hot day.

More movement of air → the moist layer above the cloth is swept away → faster

evaporation

Why the wind helps so much:

1. As water evaporates, a thin layer of very humid air forms right against the wet cloth.
2. If that layer stays there, it soon becomes full of vapour and evaporation almost stops.
3. Wind blows this saturated layer away and replaces it with fresh, drier air.
4. So the surface of the cloth is always facing dry air, and water keeps leaving it at full speed.

Note the important difference from sunlight: the wind does not add heat — a
breeze is usually cooler than still air. It speeds up drying by removing the vapour,
not by warming the water. This is a very common misunderstanding, and question 5
of the exercises is built on it.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Everyday proof: this is why washing is hung in an open, breezy place rather than in
a closed bathroom, and why the same clothes on the same day dry faster on the
terrace than on a balcony sheltered by walls.

Q3 If you want to dry your clothes on a rainy day, how can you make it faster?

On a rainy day the air is already very humid, so we must work on the other three conditions —
area, air movement and temperature.

WHAT TO DO WHICH CONDITION IT USES

Wring or spin-dry the clothes hard first Removes most of the water before drying
even begins

Spread each garment out fully on a wide line or a stand, never Increases the exposed area
bunched or folded

Hang them apart with gaps between garments Lets air reach both sides

Switch on a fan or hang them in a through-draught between Increases air movement and sweeps away
two open windows the humid layer

Dry them in a warm room, or press them with a hot iron, or Raises the temperature
use a hair dryer or a machine dryer

Do not dry them in a small closed bathroom The trapped air becomes saturated and
drying stops

Why humidity is the villain here: if the amount of water in the air is already high
(more humidity), water evaporates slowly. The air simply has little room left to take in
more vapour. We cannot change the weather, but a fan and a well-spread garment
can still get the job done.

Do you know? The amount of water vapour in the air is more on rainy days, and
hence rainy days are more humid. That is also why a rainy day feels sticky — sweat
does not evaporate, so our body cannot cool itself easily.

In-text Questions — Page 156

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

8.6 Cooling Effect

Q1 Aavi asks, “Why is the water in the earthen pot so cold? I never observed water
getting cold in a stainless steel pot.” What do you think is the reason?

The reason is evaporation, and the cooling effect it produces.

1. An earthen matka is made of baked clay, which is full of very fine pores.
2. Water slowly seeps through these pores and appears as a thin film of moisture on the outer
surface — that is why a matka always feels a little damp.
3. This film of water evaporates into the air.
4. To evaporate, water needs heat, and it takes that heat from the pot and from the water
still inside it.
5. Losing heat, the water inside becomes cooler — and the process goes on all day.

Why a stainless steel pot does not do this: steel has no pores. No water can reach the outer
surface, so there is nothing to evaporate and no heat is taken away. The water inside simply
stays at room temperature.

Water seeps out through the pores → evaporates → takes heat from the pot and the water

inside → the water becomes cold

Why the matka works best in dry summer heat: evaporation is fastest when the
air is hot and dry and moving. That is exactly the weather in a Rajasthan or
Vidarbha summer, which is why a matka can keep water several degrees cooler than
the room. During the humid monsoon the same matka cools far less, because
evaporation slows down.

Tip: Keep the matka in a shaded, airy place and cover it with a wet cloth. Both
increase evaporation from the outside and make the water inside even colder. Never
wrap it in plastic — that stops evaporation and defeats the whole purpose.

Q2 What are the other examples of cooling effect?

Anywhere water evaporates, cooling follows. The chapter itself names sprinkling water on the
floor or the roof in summer. Here is a fuller list:

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

EXAMPLE WHAT EVAPORATES, AND WHAT GETS COOLED

Sweating Sweat evaporates from the skin and takes heat from our body — this is how
the body controls its temperature

Sitting under a fan Moving air makes the sweat evaporate faster, so we feel cooler even though
the fan adds no coldness

Matka and surahi Water seeping through the clay evaporates and cools the water inside

Sprinkling water on the floor or The water evaporates and cools the floor and the air just above it
the terrace

Hanging wet khus or jute Air passing through is cooled as the water in the curtain evaporates
curtains at the door

Desert cooler Air is drawn through wet pads; the water evaporates and the air comes out
cool

Sanitiser or spirit on the skin The alcohol evaporates very fast and the palm feels cold

A wet cloth on the forehead in Water evaporating from the cloth carries heat away from the head
fever

A dog panting; a buffalo lying in Water evaporating from the tongue or the wet skin cools the animal
a pond

The single rule behind all of them: evaporation is a cooling process. A liquid
cannot turn into vapour without taking in heat, and it takes that heat from whatever
it is touching — skin, clay, floor or air.

Q3 How do you feel when you rub sanitiser on your hands?

The palm feels distinctly cold, and the coldness is strongest just as the sanitiser is disappearing.
Blowing on the hand makes it feel colder still.
Why:

Sanitiser is mostly alcohol, which evaporates very quickly at room temperature.
Rubbing spreads it into a thin film, so the exposed area is large and evaporation is very fast.
The evaporating liquid takes the heat it needs from your skin, so the skin loses heat and
feels cold.
Blowing adds air movement, which speeds the evaporation up further — hence the extra
chill.

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Class 6 Science Chapter 8 A Journey through States of Water
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co m
m.
The connection Aavi makes: Now, I can understand why we feel cooler if we sit under

m l a se
a fan! The wind helps the sweat to evaporate and cools us. Sanitiser on the palm and
o g blow cold air, it
c body work in exactly the same way — the fan doesanot
sweat on .the
m
e the liquid evaporate.
shelps
l a
ag
only

o m
c ag
Try This — this is also the first Learning further task: wet one hand and leave the
other dry, then blow across both. Onlym .
s e the wet hand feels cold, which proves that the
a water and not from the air being cold.
agl
cooling comes from the evaporating

co m
e m.
com (Fig. 8.7) and the surahi (Fig. 8.8)
Activity 8.9: Let us make a model — Pages 156 and 157
g l as
A pot-in-pot .cooler a
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ACTIVITY

m a s
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Q1 Observe and discuss how it creates a cooling effect inside the pots.

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ANSWER a

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The pot-in-pot cooler is nothing but a large matka working on a bigger scale. Recall how it is

centre, more sand filling the gap, water poured into the sand, and a e
.
built: a large earthen pot, a layer of sand at its bottom, a smaller earthen pot placed in the
mor a wet jute sack
m a s lid

. co a gl
emthe cooling happens, step by step:
on top.

a s
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How
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1. The wet sand keeps the outer pot damp all the time.

a se
com l
2. Water seeps through the pores of the outer pot and reaches its outer surface.
. a g
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3. There it evaporates into the surrounding air.
s heat is drawn from the outer pot, the sand, the inner pot
4. Evaporation needs heat, andathat
a g l
and the things kept inside.

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5. So the inside of the smaller pot becomes several degrees cooler than the room, and the wet

. co
m
jute sack on top does the same job for the opening.

as e
om at any stage. l
6. Adding water regularly keeps the sand moist, so the process never stops. No electricity is
.cused a g
se m
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a c
Wet sand → water seeps to the outer surface → evaporates → takes heat from inside →
m .
m a s e
. co agl
vegetables and fruits stay cool and fresh
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g l as
a

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Why the sand is there at all: the sand acts as a reservoir. It holds a large quantity
of water and feeds it steadily to the outer pot, so evaporation continues for hours
instead of stopping in a few minutes. It also keeps the two pots apart, so the cool
inner pot is not directly touching the warm air.

Did you know? This design is known worldwide as the zeer pot. It can keep
tomatoes and leafy vegetables fresh for many days in a village that has no electricity,
and it has been used to store medicines in hot, remote areas.

Q2 Keep some vegetables and fruits in it and observe for a week on a daily basis. For
how many days can the vegetables and fruits be kept fresh in it? What are the
conditions which can affect the number of these days?

Roughly what you will find: in an ordinary Indian summer a well-made pot-in-pot cooler keeps
most vegetables fresh far longer than the open kitchen shelf.

ITEM KEPT ON AN OPEN IN THE POT-IN-POT
SHELF COOLER

Tomato, brinjal, capsicum 2–3 days About 8–12 days

Spinach, coriander and other leafy Less than 1 day About 3–5 days
greens

Carrot, beans, lady finger 2–4 days About 7–10 days

Guava, banana, grapes 2–3 days About 5–8 days

Conditions that change the number of days:

How dry the air is. Hot, dry air gives fast evaporation and the best cooling. In humid
monsoon weather the cooler works much less well.
Movement of air. Standing the cooler in a breezy, shaded spot cools it far better than a
closed corner.
Sunlight. Direct sun heats the pot faster than evaporation can cool it — always keep the
cooler in the shade.
How regularly you add water. If the sand dries out, the cooling stops at once.
Quality of the pots. Unglazed, well-fired clay is porous and works well; a glazed or painted
pot has sealed pores and hardly cools at all.
The covering. A wet jute sack works better than a dry lid, as it evaporates too.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

What you put in, and how much. Only fresh, dry, undamaged produce should go in, and
the pot should not be packed so tight that air cannot move.

Tip: Keep an identical set of vegetables outside the cooler as a control and compare
them every day. Without the comparison you cannot claim that the cooler made any
difference.

Q3 What else can be used in place of sand for better cooling?

The material in the gap has just one job — to hold a lot of water and keep the outer pot wet.
So anything that soaks up water well and stays in contact with the pot will do, and some
materials do it better than sand.

MATERIAL HOW WELL IT WORKS

Khus (vetiver) roots Excellent — holds a great deal of water, lets air pass through, and adds a
pleasant scent. Used in traditional coolers

Wet jute or gunny cloth, Very good — soaks up much more water than sand for the same weight
packed in layers

Coir (coconut husk fibre) or Very good — holds many times its own weight of water
coco peat

Sawdust or dry straw Good, and easily available in villages

Charcoal pieces Good — porous, holds water and also keeps smells away

Sand (the standard choice) Works, is cheap and easy, but holds less water than the materials above

Clay soil or cotton wool Poor — clay packs solid and blocks air; cotton stays soggy and rots

What makes a material good here: two things together — it must hold plenty of
water (so the supply lasts) and it must be loose enough for air to move through
(so the water can actually evaporate). Sand is only average on the first count, which
is why khus roots and coir work better.

Page 46 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Try This: Make two small coolers, one with sand and one with wet jute, and measure
the temperature inside each with a laboratory thermometer after 5 hours. Report
both readings in °C — that turns your model into a real experiment.

In-text Questions — Page 157
8.7 How do Clouds give us Rain?

DO YOU KNOW?

Q1 Condensation plays a significant role in the process of bringing evaporated water
back to the Earth's surface. How does this happen?

It happens in five stages — and the whole of it is just evaporation followed by condensation,
on the scale of the sky.

1. Water goes up. Water evaporates from oceans, rivers, lakes, wet soil, plants and wet clothes,
and rises with the air as invisible water vapour.
2. The air cools as it rises. As the book says, when air moves higher above the Earth's surface, it
becomes cooler and cooler.
3. Condensation. At a certain height the air gets so cool that the vapour in it turns into tiny
droplets. These droplets generally form around dust particles floating in the air.
4. Clouds. These small droplets are light enough to float, and countless numbers of them
together are what we see as a cloud.
5. Rain. Many droplets join together to form bigger drops. Some drops become so heavy that
the air can no longer hold them up and they start falling — and these falling water drops are
what we call rain. Under special conditions they fall as hail or snow instead.

Evaporation → rising, cooling air → condensation on dust particles → droplets float as

cloud → droplets merge → too heavy → rain, hail or snow

Why dust particles matter: vapour finds it hard to start forming a droplet in
perfectly clean air. A speck of dust, salt or smoke gives it a surface to gather on.
Activity 8.10 proves this beautifully — the bottle stays clear until a pinch of smoke
from burnt newspaper is added, and only then does a haze appear.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Do you know? Why does air containing water vapour go up in the atmosphere at
all? Gas balloons containing lighter gases go up in the air. Similarly, water vapour is
lighter than air, causing it to rise. Warm, moist air is lighter than the cool dry air
around it, so it floats upward — and the atmosphere is the thin layer of air that
surrounds the Earth.

Q2 Why does air containing water vapour go up in the atmosphere (thin layer of air
that surrounds the Earth)?

Because water vapour is lighter than air, so moist air rises — exactly as a balloon filled with a
light gas rises.
Two things push it upward:

Moist air is lighter than dry air. The book compares it with gas balloons: as we know, gas
balloons containing lighter gases go up in the air. Similarly, water vapour is lighter than air,
causing it to rise.
Warm air is lighter than cool air. Air near a sun-baked ground or a warm sea gets heated,
expands, becomes lighter and floats up, carrying its vapour with it. Cooler, heavier air slides
in below to take its place.

Why this matters for rain: unless the moist air goes up, it never gets cold enough
for its vapour to condense. The rising is what supplies the cooling. This is why hills
and mountains, which force moving air to climb, get so much rain — the Western
Ghats and the Khasi hills of Meghalaya are the classic Indian examples.

Check it yourself: Hold a strip of thin paper above a lighted lamp or a warm stove
(at a safe distance). It flutters upward, showing the rising current of warm air. The
same current carries water vapour to the height of the clouds.

In-text Question — Page 158

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Class 6 Science Chapter 8 A Journey through States of Water
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Aavi's poem about the journey of water
co m
e m.
m l as
Q1
.co a g
Aavi enjoys the rain and creates a poem. You can complete the poem and present it
m class. [I wonder, oh! I wonder so, / Which path does water choose to go? … I
ineyour
a s
a gl wonder, ponder and dream each day, / As water's journey takes its way.]

. com ag

a s em and rhyme, and must add one more stage of
The two blank lines must keep the same rhythm

agl version you can adapt.
the water's journey. Here is a completed

co m
m.
I wonder, oh! I wonder so,

m as e
.co
Which path does water choose to go?
a g l
se m
a
I wonder, oh! I wonder so,

a g l When does it snow?

m a s
.co agl
I wonder, oh! I got a wonder call,

se m
a
How does rain fall?

I wonder, oh! I wonder still,ag
l

m
How does it climb the highest hill?
. co
e m
as
I wonder, ponder and dream each day,

com journey takes its way.
As .water's a g l
m
ase
agl Other pairs of lines that fit just as well:
se m
com g l a
.
"I wonder, oh! I wonder near, / Why do the drops on the glass appear?"
m a
ase
"I wonder, oh! it makes me stare, / How does the puddle melt in air?"

agl
"I wonder, oh! at break of day, / Why do the dewdrops slip away?"

What makes a good completion here: the poem is a chain of questions about the
co m
m .
e
water cycle, not statements. Each pair of lines names one stage — snow, rain,
m l as
.co g
evaporation, condensation, the river running back to the sea — and ends with a

e m rhyme. Keep the questioning tone, because the whole chapter is about askinga
la s
ag questions before finding answers.
c
m .
m a s e
. co
Tip for presenting it: read it with four friends, each taking one stage of the water
a gl
s m
edrawing — sea, cloud, rain, river — as your line comes.
a
gl water cycle and sees it at the same time.
cycle, and hold up a simple
The class then hearsathe

co m
m .
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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Activity 8.10: Let us engage in a group activity — Page 158
Making a cloud inside a plastic bottle

ACTIVITY

Q1 Pour about one cup of water into an empty one litre plastic bottle, close the lid
tightly, squeeze and release the bottle continuously for about 2–3 minutes and
observe the space above the water in the bottle. What will you observe?

Almost nothing happens. The space above the water stays clear, or at most a very faint
mistiness appears for a fraction of a second when you release the bottle, and it vanishes at
once.
What is going on inside:

Squeezing raises the pressure of the air inside; releasing it suddenly lowers the pressure,
and the air inside cools a little.
The air in the bottle certainly contains water vapour from the water below.
But there is nothing for the vapour to condense on. The air inside a clean bottle has very few
dust particles.
So no lasting cloud forms.

Why this first, failed step is the important one: it is the control. Without it, when
the cloud appears in the second half of the activity you could not say what caused it
— the squeezing, the water, or the smoke. Doing it first without smoke shows clearly
that cooling alone is not enough.

Caution: use an empty, discarded bottle with a lid that closes tightly, and do not
squeeze so hard that the lid pops off.

Q2 Repeat the same activity after adding a small burnt piece of newspaper into the
water. What will you observe, and why does this happen?

Now a cloud appears. As the book says — in this case, you will observe some haziness (clouds)
above the water in the bottle. Squeeze and the haze clears; release and it comes back, again and
again.
Why it happens:

Page 50 of 70

Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

1. The burnt newspaper releases very small, invisible dust and smoke particles into the
bottle.
2. When the bottle is released, the air inside expands and cools.
3. The water vapour in the cooled air now has something to gather on, so it condenses around
these tiny particles and forms countless minute droplets.
4. Those floating droplets are exactly what a cloud is — hence the haziness.
5. Squeezing again warms and compresses the air, the droplets evaporate, and the bottle
clears.

Cooling + water vapour + dust particles → tiny droplets → cloud

What the activity demonstrates: it shows the role of dust particles in the
formation of clouds. In the sky the same job is done by dust blown off fields and
deserts, salt particles from sea spray, smoke and pollen. This is why real air, which is
never perfectly clean, forms clouds so readily.

Caution: handle the burning paper carefully, do it under a teacher's supervision,
and drop the burnt bit into the water so that it is put out at once.

Activity 8.11: Let us understand the process — Page 159

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Fig. 8.9 Change of states and movement of water — the water cycle

ACTIVITY LET US REFLECT

Q1 Label Fig. 8.9 using arrows shown and the words given in the box to show where
water is stored, how water changes its state and where it moves. [Cloud, Lake,
Ocean, River, Groundwater, Evaporation, Condensation, Rain, Snow]

Cloud, Lake, Ocean, River, Groundwater, Evaporation, Condensation, Rain, Snow

Fig. 8.9, page 159 — redrawn sketch: change of states and movement of water. The
arrows are the ones printed in the book; the words above are the ones you have to
place.

Here is the figure with all nine words placed correctly.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Condensation

Cloud
Snow

Rain
Evaporation

River Lake

Ocean
Groundwater

The water cycle. Water evaporates from the ocean, rivers, lakes and wet land; the rising air cools and
the vapour condenses around dust particles to form clouds; the droplets join and fall as rain, hail or
snow; the water collects in lakes and rivers, soaks in as groundwater, and finally flows back to the
ocean.

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Class 6 Science Chapter 8 A Journey through States of Water
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WORD FROM THE WHERE IT GOES ON THE FIGURE WHAT IT SHOWS
BOX
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Ocean
a s em The large body of water on the left Where water is stored — most of the

ag l Earth's water

Evaporation On the upward arrows from the ocean and from Change of state: liquid → gas

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the wet land

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Condensation
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At the cloud that is forming, high in the air Change of state: gas → liquid

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Cloud The floating masses of tiny droplets Where water is stored in the sky

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Rain On the downward arrows and droplets below Water moving back to the Earth

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the dark cloud

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Snow On the white cap of the mountain Water stored in the solid state

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ocean

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Lake The still body of water Water stored on the surface

Groundwater The bandagbelow the land surface, with arrows Water stored under the ground

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circulation

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Why it is called a cycle: there is no beginning and no end, and no new water is
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ever made. The same water goes round and round — the water in your glass today
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before it reached you. That is also why wasting or polluting water matters so much:
we cannot manufacture more.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

Sample answer: What I did well: I labelled the ocean, the cloud, the rain, the river
and the snow on the mountain without help, and I got all the arrows pointing in the
right direction — upward for evaporation, downward for rain. Was I able to label all
the parts? Yes, all nine, but I had to think twice about groundwater. What was
unclear: I first wrote "condensation" next to the rain instead of next to the forming
cloud. I now understand that condensation is the moment the vapour becomes
droplets and makes the cloud, while rain is what happens later, when the droplets
have joined into drops heavy enough to fall.

Points worth checking in your own diagram:

Does the arrow for evaporation point upward, and the arrows for rain point downward?
Is condensation marked where the cloud forms, not where the rain falls?
Is groundwater shown below the land surface?
Does the river end in the ocean, completing the circle?
Have you shown that evaporation happens from the land, lakes and rivers too, not just
from the sea?

Why reflection is part of science: knowing exactly which step you got wrong is
more useful than knowing your score. The chapter has used the same habit
throughout — observe, question, guess, test, and then look back at what worked.

Let us enhance our learning — Pages 161 and 162
Chapter exercises

LET US ENHANCE OUR LEARNING

Q1 Which of the following best describes condensation? (i) The conversion of water into
its vapour state. (ii) The process of water changing from a liquid into gaseous state.
(iii) The formation of clouds from tiny water droplets. (iv) The conversion of water
vapour into its liquid state.

Answer: (iv) The conversion of water vapour into its liquid state.
This is the chapter's own definition — the process of conversion of water vapour into its liquid state
is called condensation.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

OPTION WHY IT IS RIGHT OR WRONG

(i) Conversion of water into Wrong — this is evaporation, the opposite process
its vapour state

(ii) Water changing from a Wrong — this is again evaporation, only in different words
liquid into gaseous state

(iii) Formation of clouds from Wrong — this is a result of condensation, not condensation itself. Condensation is
tiny water droplets what makes the droplets in the first place; the cloud is what those droplets look like

(iv) Conversion of water vapour Correct — gas → liquid, which happens whenever vapour meets a colder
into its liquid state surface

Tip for eliminating options: read the direction of the change. Condensation must
go gas → liquid. Options (i) and (ii) both go liquid → gas, so they can be struck out at
once. Between (iii) and (iv), pick the one that describes the process rather than its
outcome.

Q2 Identify in which of the given processes, evaporation is very important— (i)
Colouring with (a) crayons (b) water colours (c) acrylic colours (d) pencil colours; (ii)
Writing on paper with (a) pencil (b) ink pen (c) ball point pen

(i) Colouring — the answer is (b) water colours.

COLOURING IS EVAPORATION INVOLVED?
MEDIUM

(a) Crayons No — a crayon is solid wax rubbed on to paper. Nothing has to dry

(b) Water colours Yes, very important — the pigment is mixed with water. The picture is finished only
when the water evaporates and leaves the colour on the paper

(c) Acrylic colours Evaporation of water does take place, but the colour also sets by the acrylic hardening. Water
colours are the clearer answer

(d) Pencil colours No — solid coloured leads, nothing wet at all

(ii) Writing on paper — the answer is (b) ink pen.

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

WRITING IS EVAPORATION INVOLVED?
TOOL

(a) Pencil No — solid graphite leaves a mark straight away, with nothing to dry

(b) Ink pen Yes, very important — fountain-pen ink is a thin, water-based liquid. The writing smudges
until the water in the ink evaporates, which is why blotting paper was once needed

(c) Ball point Very little — ball pen ink is a thick, oily paste that dries almost at once and hardly depends on
pen evaporation

The rule to apply: ask whether the material is put on the paper as a liquid that has
to dry. If yes, evaporation is essential; if the material is already solid, evaporation
plays no part.

Check it yourself: Write one line with a fountain pen and one with a ball pen, and
touch both after five seconds. The fountain-pen line smudges; the ball-pen line does
not.

Q3 We see green coloured plastic grass at many places these days. Space around
natural grass feels cooler than space around the plastic grass. Can you find out
why?

Because natural grass is full of water and keeps losing it by evaporation, while plastic
grass has no water at all.

NATURAL GRASS PLASTIC GRASS

Water present Yes — in the leaves, in the soil below and in the None at all; the ground beneath is usually
dew on it a sealed mat

Evaporation Constant — water escapes from the leaves None
and from the moist soil

Effect on heat Evaporation takes heat from the leaves and the All the heat absorbed stays there and is
air, cooling both passed on to the air

Behaviour in Stays fairly cool; you can walk on it barefoot at Gets very hot — plastic absorbs sunlight
sunlight noon and heats up quickly

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Class 6 Science Chapter 8 A Journey through States of Water AglaSem · NCERT Solutions

The science in one line: evaporation is a cooling process. Every gram of water
leaving the grass carries heat away with it, so a natural lawn behaves like a huge,
silent, electricity-free cooler. Plastic grass has nothing to evaporate, so it simply
absorbs sunlight, becomes hot and warms the air above it.

Check it yourself: On a sunny afternoon, place a laboratory thermometer just above
a real lawn and then just above a plastic mat, waiting two minutes each time. Note
both readings in °C — the difference is often more than 10 °C.

Q4 Give examples of liquids other than water that evaporate.

Many liquids evaporate, and several of them do so much faster than water.

LIQUID WHERE YOU MEET IT HOW FAST IT EVAPORATES

Spirit / alcohol Hand sanitiser, the swab before Very fast — the skin feels cold at once
an injection

Acetone Nail-polish remover Very fast, with a strong smell

Petrol At the petrol pump Very fast — you can smell it several metres
away

Kerosene and diesel Lamps, stoves, vehicles Fast

Perfume, deodorant, Applied on the skin Fast — which is exactly why we can smell it
attar

Turpentine and With oil paints Fast
thinner

Milk, buttermilk, tea In the kitchen Slow — only the water in them evaporates,
solids are left behind

Vinegar, lemon juice In cooking Slow

Coconut oil, mustard In every home Very slow, but they do evaporate over months
oil

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Class 6 Science Chapter 8 A Journey through States of Water
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co m
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Why different liquids evaporate at different rates: the particles of some liquids

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are held together far less strongly than those of water, so they escape more easily at
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the same.temperature. a g acetone and
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Such liquids are said to be volatile — spirit,

l a seare the everyday examples. That is also why their bottles must always be kept
g closed and away from flames.
petrol
atightly

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Q5 Fans move air around, creating a cooling sensation. It might seem strange to use a
fan to dry wet clothes since fans usually make things cooler, not warmer. Normally,

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when water evaporates, it requires heat, not cold air. What do you think about this?
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There is no contradiction here at all. The puzzle disappears once we see that a fan does not

g
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supply the heat for evaporation, and it does not need to.

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1. Where does the heat come from? Not from the fan. The heat needed for evaporation is

a s em
taken from the wet cloth itself and from the surrounding air, which are already at room

a gl That is more than enough; evaporation does not need
temperature — say 30 °C or more.
boiling at 100 °C.
2. What does the fan actually do? As water evaporates, a layer of very humid air collects right
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against the cloth and blocks further evaporation. The fan keeps sweeping this saturated

cominstead of stalling. g l as
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layer away and brings fresh, drier air to the surface. So evaporation can carry on at full
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speed
a 3. Why does a fan then feel cool on our skin? For exactly the same reason. It makes the
agl sweat on our body evaporate faster, and the evaporating sweat takes heat from our skin.

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The air blown by the fan is not cold — a thermometer held in front of a fan shows the same

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room temperature.

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Fan → removes the humid layer of air → faster evaporation

Faster evaporation from cloth → clothes dry sooner
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Faster evaporation from skin → heat taken from the body → we feel
. co a
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agl The single idea behind both: the fan speeds up evaporation, nothing else.
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Whether that shows up as "drying" or as "cooling" depends only on what the water is
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evaporating from — a shirt or your skin.
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