NCERT Solutions Class 6 Science Chapter 7 Temperature and Its Measurement

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 7: Temperature and its
Measurement

NCERT Textbook — Curiosity

BOOK PAGES SECTIONS QUESTIONS MEDIUM

123 – 141 16 50 English

Solutions, notes, sample papers & more at 55 pages

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

CLASS 6 · SCIENCE · CURIOSITY

NCERT Solutions — Chapter 7: Temperature and its
Measurement
Complete NCERT Solutions for Class 6 Science Chapter 7 Temperature and its Measurement from the
NCERT textbook Curiosity. Every question of the chapter is answered — the seven Activities 7.1 to 7.7, the
More to do! task, all the in-text question boxes from pages 123 to 135, and all 14 questions of Let us
enhance our learning along with Learning further. Every thermometer scale in the book has been read off
the printed page, and every temperature is written with its correct unit, °C.

TEXTBOOK BOOK PAGES

Curiosity (Class 6) 123 – 141

SECTIONS QUESTIONS

16 50

MEDIUM

English

In-text Questions — Page 123
Chapter opening — 7.1 Hot or Cold?

Q1 Can it always be correctly judged, that a person has fever, only by touching the
person?

No. Touching can only give a rough hint. It can never tell us how much the temperature is, and it
can easily be wrong.

Why it happens: when you touch someone’s forehead, your skin does not measure
temperature — it only compares the forehead with your own hand. If your hand is
cold (say you have just washed clothes in cold water), a perfectly normal forehead
will feel hot. If your hand is warm, a person with mild fever may feel normal.

This is exactly what happens in the story at the start of the chapter:

Phiban touched Lambok’s forehead and felt that he might be having a fever.
She then used a thermometer — and found his temperature was normal.

A thermometer gives a number, such as 37.0 °C or 38.5 °C, which can be compared with the
normal value of 37.0 °C. Touch gives no number at all.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Tip: A mild fever may raise the body temperature by less than 1 °C. Your skin simply
cannot notice such a small change — but a thermometer can.

Activity 7.1: Let us investigate — Page 124
7.1 Hot or Cold?

ACTIVITY

Q1 Write down your predictions. — What will my right hand feel on dipping it in B?

Prediction: the right hand will feel that the water in B is cool (cold).
Remember what each container holds:

CONTAINER WHAT IS IN IT WHICH HAND WAS IN IT

A Warm water Right hand, for 1–2 minutes

B Tap water Both hands together, afterwards

C Ice-cold water Left hand, for 1–2 minutes

Why it happens: the right hand has been sitting in warm water, so it has become
used to warmth. Tap water in B is cooler than the warm water in A, so to that hand B
feels cool.

Q2 What will my left hand feel on dipping it in B?

Prediction: the left hand will feel that the water in B is warm.

Why it happens: the left hand has been sitting in ice-cold water. Tap water in B is
warmer than the ice-cold water in C, so to that hand the very same water feels
warm.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

So the two hands are placed in one and the same bowl of water at the same moment, and they
report two opposite things.

Q3 Now, conduct the activity and write your observations.

Observation: the predictions come true. Water in B is a single sample at a single temperature,
yet

HAND WAS EARLIER IN WHAT IT FEELS IN B

Right hand Warm water (A) Cool

Left hand Ice-cold water (C) Warm

Conclusion: Our sense of touch cannot always be relied upon to decide correctly whether a
body is hot or cold.

Why it happens: the skin does not sense temperature. It senses the flow of heat
between the object and itself. Heat flows out of the warm right hand into the tap
water, so that hand says “cool”; heat flows from the tap water into the cold left hand,
so that hand says “warm”. Both hands are honest — they are simply answering a
different question from the one we asked.

Check it yourself: put a steel tumbler and a woollen cap side by side in the same
room. The steel feels colder — yet a thermometer shows both at the same room
temperature. Steel simply carries heat away from your hand faster.

In-text Questions — Page 125
7.1 Hot or Cold? / 7.2 Temperature

Q1 Compare whether your observations match with your predictions. Did your right
hand feel that the water in container B is cool, while your left hand felt that the
same water is warm? What do you infer from these observations?

Yes — the observations match the predictions. The right hand felt B cool and the left hand
felt the same water warm.

Page 3 of 55

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Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

The inference:
co m
e m.
m l as
m .co
The same water gave two different answers at the same moment.
a g
l a se
g
Therefore the feeling of hotness depends on the hand, not only on the water.
aWe cannot always rely upon our sense of touch to decide whether a body is hot or cold.

co m
em . ag
g l as
Why this matters in science: a measurement must give the same result no matter
a
who takes it. Touch fails this test, so science needs an instrument and a number — a

m
thermometer and a temperature in °C.
co
em.
m l as
m .co a g
l a
Q2 se Then how do we find out how hot or cold a body is?

a g
m a s

By measuring its temperature with a thermometer.
m .co agl
l a se
a g
Temperature is a reliable measure of the hotness (or coldness) of a body.
A hotter body has a higher temperature than a colder body.
The difference in temperature between two bodies tells us how much hotter one is than the
co m
other.
m .
m as e
.co
The device that measures temperature is called a thermometer.
a g l
se m
a
You will meet two kinds in this chapter:

ag l
se m
THERMOMETER USED FOR

m temperature
cobody g l a
. a
em
Clinical thermometer Human

a s
l Many other purposes — water, air, chemicals
Laboratory thermometer
ag

co m
Tip: “Hot” and “cold” are opinions; “42.5 °C” is a measurement. Science prefers the
m .
m
second.
as e
.co a g l
se m
g l a
a c
m .
e
In-text Questions — Page 126
m a s
e m . co agl
g l as
a

co m
m .
m ase
.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

7.3.1 Clinical thermometer

DO YOU KNOW?

Q1 During the COVID-19 pandemic, some special thermometers were used, which could
measure the temperature of a person from a distance. What were those?

They were non-contact thermometers, also called infrared thermometers.

They measure a person’s temperature without touching the body — you may have seen
one held near the forehead or the wrist at a school gate, a railway station or a hospital.
Because there is no touching, the same instrument can be used on hundreds of people one
after another and it reduces the risk of spreading disease.
They give the reading in a second or two on a digital display, usually in °C (some can be
switched to °F).

Why it works: every warm body gives out invisible infrared radiation. The hotter the
body, the more it gives out. A sensor inside the instrument catches this radiation and
the electronics convert it into a temperature reading.

Did you know? A digital contact thermometer works differently — it has a heat
sensor at its tip that must actually touch the body, which is why it takes longer and
must be washed before and after each use.

Activity 7.2: Let us measure — Page 127

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

7.3.1 Clinical thermometer

ACTIVITY

Q1 Let us now use a digital clinical thermometer to measure body temperature. You
may measure your own temperature as well as the temperature of some of your
friends… Record the temperature in Table 7.1.

S. NO. NAME TEMPERATURE (°C)

1.

.

.

.

.

10.

Table 7.1, page 127 — Body temperatures of 10 persons. The table is printed blank; fill in
your own readings.

The steps, in order:

1. Wash your hands and the tip of the digital thermometer with soap and water.
2. Reset the thermometer by pressing the reset button.
3. Place the thermometer under the tongue and close your mouth.
4. Wait till it gives a beep or flashes a light.
5. Take it out and read the temperature on the digital display.
6. Record it in Table 7.1, clean and dry the tip, and repeat for the next friend.

Sample answer (your own table will have your classmates’ names and their own readings):

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

S. NO. NAME TEMPERATURE (°C)

1. Ananya 36.8 °C

2. Ravi 37.0 °C

3. Meenakshi 36.9 °C

4. Imran 37.2 °C

5. Kavya 36.6 °C

6. Tenzing 37.1 °C

7. Suresh 36.7 °C

8. Phiban 37.0 °C

9. Deepa 36.9 °C

10. Arjun 37.3 °C

Notice that the ten readings are not all the same, but they all lie close to 37.0 °C — between
about 36.6 °C and 37.3 °C here.

Precautions (the book’s own list): read the instruction manual first; wash the tip
with soap and water before and after use; while washing, keep the digital part (the
display) out of the water; and never hold the thermometer by its tip.

In-text Questions — Page 128
7.3.1 Clinical thermometer

Q1 The normal temperature of a healthy human body is taken to be 37.0 °C. But in this
activity, did you find that the normal temperature of every person was 37.0 °C? Or
did you find the temperature slightly higher or lower for some people?

No, every person did not read exactly 37.0 °C. Some readings were a little higher and some a
little lower — in the sample table above they ranged from about 36.6 °C to 37.3 °C, all of these
being perfectly healthy children.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Why it happens: 37.0 °C is not a rule that every body must obey. It is the average
body temperature of a large number of healthy people. Since it is an average, most
healthy people lie a little on either side of it.

The body temperature of a person is influenced by:

Age — small children usually a little higher, old people a little lower;
Time of the day — usually lowest in the early morning, highest in the evening;
Activity level — higher just after running or playing.

Whatever these variations, human body temperature does not normally go below 35 °C or
above 42 °C.

Try This: Measure your own temperature at the same three times every day (say 7
am, 1 pm and 7 pm) for a month and write the readings in your notebook. You will
see a small daily rise and fall of a few tenths of a degree — even though you were
healthy all month.

Q2 Do small children generally have slightly higher body temperatures as compared to
adults?

Yes. Small children generally have a body temperature that is a little higher than that of adults
— often a few tenths of a degree Celsius above the adult average.

Why it happens: a small child’s body is more active in building itself up, so it
produces heat faster for its size. At the same time a child is small, so the body must
keep a slightly higher temperature to balance the heat it loses. This is normal and is
not fever.

Tip: Because the difference is small, do not call it fever from touch. Measure it.
Doctors usually treat a reading clearly above 38 °C as fever, whatever the age.

Page 8 of 55

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Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

co m
m.
Do old people, even when healthy, generally have lower body temperatures than
e
Q3

m l as
.co
young adults?

a g
se m
g l a
a

Yes. Healthy old people generally show a body temperature that is slightly lower than that of

m
young adults.
. co ag
e m
g l as
Why it happens: as age advances, the body produces heat a little more slowly and
a
controls its temperature slightly less sharply. So the “normal” value shifts a little
downward — again by a few tenths of a degree Celsius, not by whole degrees.
co m
se m.
different.c o m l a
This is why the book says a perfectly healthy person may have a normal temperature slightly
g it.
m a
from 37.0 °C, and lists age as one of the factors that influence

l a se
ag Did you know? For very small children and for old people, the digital thermometer
may also be placed in the armpit. A reading taken this way is about 0.5 °C to 1 °C
m a s
.co
lower than the actual body temperature, so that much has to be allowed for.
m agl
l a se
a g
Q4 I have seen a friend of mine using a digital thermometer that reads temperature on
co m
m .
e
a different scale. It shows the normal temperature of a healthy human body as 98.6

m l as
.co g
°F. What is the reason for this difference?

em a
a s
agl ANSWER

m
Because that thermometer is showing the same temperature on a different scale — the

a se
com l
Fahrenheit scale, whose unit is degree Fahrenheit, written °F.
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m
ase
Normal body temperature
agl
= 37.0 °C on the Celsius scale

co m
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= 98.6 °F on the Fahrenheit scale
m l as
m .co a g
Same hotness — two different numbers, because the two scales are marked differently.

l a se
ag
.c
m
Why it happens: a scale is only a set of marks that somebody chose. On the Celsius

m a s e
co agl
scale, melting ice is marked 0 and boiling water is marked 100, so there are 100

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steps between them. On the Fahrenheit scale the same two points are marked 32

g l as
and 212, so there are 180 steps between them. A Fahrenheit degree is therefore a
a
smaller step than a Celsius degree, and the numbers come out bigger.

co m
m .
m ase
.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

It is like measuring the same cloth in metres and in centimetres — 1.5 m and 150 cm are the
same length written two ways.

Did you know? There is a third scale used in scientific work, the Kelvin scale, whose
unit is the kelvin (K) — and the kelvin is the SI unit of temperature. Temperature in
K = temperature in °C + 273.15, so 37.0 °C = 37.0 + 273.15 = 310.15 K. Note that the
degree sign is not written with K.

In-text Questions — Page 129
7.3.1 Clinical thermometer

DO YOU KNOW?

Q1 Can a clinical thermometer be used for measuring the temperature of boiling
water? Or for measuring the temperature of ice?

No. The temperatures of boiling water and of ice are outside the range of a clinical
thermometer.

WHAT WE WANT TO ITS INSIDE A CLINICAL THERMOMETER’S
MEASURE TEMPERATURE RANGE?

Melting ice about 0 °C No — far too low

Human body about 37 °C Yes

Boiling water about 100 °C No — far too high

Why it happens: a clinical thermometer is built only for human body temperature,
which never normally goes below 35 °C or above 42 °C. Its scale therefore covers just
that small stretch. Beyond those marks there is simply nothing printed to read —
and a glass one could even crack in boiling water.

For ice and boiling water we must use a laboratory thermometer, whose range is –10 °C to
110 °C.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q2 How can we measure temperatures beyond the range of a clinical thermometer?

By using a laboratory thermometer.

The one usually kept in a school laboratory has a range of –10 °C to 110 °C.
That single stretch covers ice at 0 °C, room air, warm water, and water boiling at about 100
°C.
It is a long sealed glass tube with a bulb of liquid (alcohol coloured red, or mercury) at one
end and a Celsius scale marked along the tube.

Tip: For temperatures far outside even this range — a furnace, or the inside of a star
— scientists use other instruments altogether. The temperature at the core of the
Sun is about 15 million degrees Celsius.

Q3 How was fever detected before thermometers were developed?

By feeling the pulse rate of the person.

Fever affects the pulse rate — it usually makes the pulse faster.
This was known even in olden days in India, and a physician would judge illness by holding
the patient’s wrist.

But this method has a weakness: apart from fever, some other situations also affect the
pulse rate — running, fear, excitement, exercise. Hence pulse rate alone is not a reliable
indicator of fever.

Why the thermometer won: the pulse is an indirect clue and gives no number for
hotness. The thermometer measures the very quantity we want — the temperature
— and gives it as a number in °C that anyone can check.

Activity 7.3: Let us observe — Page 130

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

7.3.2 Laboratory thermometer

ACTIVITY

Q1 Note down the following: — What is the lowest temperature it can measure?

For the laboratory thermometer shown in Fig. 7.3a, the lowest mark on the scale is –10 °C.
To find it on your own thermometer, hold it upright and look at the bottom end of the scale,
just above the bulb. The first number printed there is the lowest temperature it can measure.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

110 °C

100 °C

90 °C

80 °C

70 °C
Range –10 °C to 110 °C

60 °C

50 °C

40 °C
Liquid column
30 °C

20 °C

10 °C

0 °C

–10 °C
Bulb (liquid store)

Page 13 of 55

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Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

A laboratory thermometer. The scale runs from –10 °C to 110 °C, so its range is 120 °C. Each small
co m
e m.
division here stands for 2 °C.

m l as
m .co a g
l a se
Check it yourself: Not every laboratory thermometer is the same. Some start at 0
g
a°C, some at –10 °C, a few at –20 °C. Always read the actual scale of the thermometer
in your hand before you use it.
com
e m . ag
g l as
Q2
a
What is the highest temperature it can measure?

co m
em.
as
m l
m .co
For the thermometer in Fig. 7.3a, the highest mark on the scale is 110 °C.
a g
l a se
g
It is found at the top end of the scale, farthest from the bulb.
a
Why 110 °C and not 100 °C: water boils at about 100 °C. The scale is carried a little
m a s
.co
past that so that boiling water — and steam just above it — can still be measured
m agl
l a se
without the liquid running off the end of the scale.
a g

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se m
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a
se m
com g l a
m . a
ase
agl

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m a s e
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a

co m
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m ase
.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q3 So, the range of this thermometer is _______ . Now look at the thermometer shown in
Fig. 7.3a carefully. Can you tell its range?

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Page 16 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

°C

110

100

90

80

70

60

50

40

30

Page 17 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

20

10

0

–10
Bulb

Fig. 7.3(a), page 130 — a laboratory thermometer. Read its scale carefully, from the
lowest mark to the highest.

The range of a thermometer is written as “lowest mark to highest mark”.

Lowest temperature = –10 °C

Highest temperature = 110 °C

Range = –10 °C to 110 °C

Size of this range = 110 °C – (–10 °C) = 110 °C + 10 °C = 120 °C

So the thermometer of Fig. 7.3a can measure any temperature from –10 °C to 110 °C, and no
temperature outside it.

Page 18 of 55

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Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

co m
m.
Tip: Do not confuse range with smallest value. Range tells you how far the

mreaches 120 °C wide and reads to the nearest 1 °C. glas
thermometer reaches; the smallest value tells you how finely it can read. This e
. c o a
m
thermometer
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a g l

om — Page 131
Activity 7.4: Let us observe and calculate
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a
7.3.2 Laboratory thermometer

ACTIVITY agl

co m
em.
Note down the following: — How much is the temperature difference indicated

as
Q1

m l
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between the two bigger marks?
a g
se m
g l a
a On the thermometer of Fig. 7.3b, the bigger (numbered) marks are 0 °C, 10 °C, 20 °C, 30 °C and

m a s
.co agl
so on.

a s em
agl°C = 10 °C – 0 °C = 10 °C
Difference between 0 °C and 10

Difference between 10 °C and 20 °C = 20 °C – 10 °C = 10 °C

co m
m .
m as e
.co l
So the temperature difference indicated between two neighbouring bigger marks is 10 °C.
a g
se m
g l a
a
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How many divisions (shown by smaller marks) are there between these two bigger
se
Q2
marks?
com g l a
m . a
gl ase
a

Count the small gaps, not the small lines. Between 0 °C and 10 °C on the thermometer of Fig.
7.3b there are 10 divisions.
co m
m .
m as e
.co a g l
se m
g l a 0 10 20
a c
m .
m a s e
e m . co agl
g l as
a 7 °C

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m .
m ase
.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

A closeup of the scale, as in Fig. 7.3b. Between the two bigger marks 0 °C and 10 °C there are 10 small
divisions, so one small division = 10 °C ÷ 10 = 1 °C.

Tip: Counting mistakes are common here. Count the spaces between marks, not the
marks themselves — 10 spaces need 11 lines. Or count the small marks strictly
between the two big ones and add 1; here 9 + 1 = 10.

Q3 How much temperature does one small division indicate?

Divide the temperature difference by the number of divisions.

One small division = temperature between two big marks ÷ number of divisions

= 10 °C ÷ 10

= 1 °C

Q4 So, the smallest value that the thermometer can read is _______ .

The smallest value that this thermometer can read is 1 °C.

What it means in practice: with this thermometer you can honestly write 26 °C or
27 °C, but you cannot write 26.5 °C — there is no mark there to read. The smallest
value (also called the least count) fixes how precisely you are allowed to report a
reading.

Page 20 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q5 Fig. 7.3b shows a closeup of a part of the thermometer shown in Fig. 7.3a. Can you
now find the smallest value that this thermometer can read?

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

40

30

20

10

0
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Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

co m
em.
m l as
m .co a g
l a se
a g

com
e m . ag
g l as –10
a

co m
e m.
m l as
.co a g
m Fig. 7.3(b), page 131 — closeup of a part of the thermometer shown in Fig. 7.3(a). Count
l a se
a g the small divisions between two numbered marks.

m a s
m .co agl
l a se
g

a
Yes — it is 1 °C. Here is the whole calculation in one place:

co m
m .
e
Temperature between 0 °C and 10 °C (or between 10 °C and 20 °C) = 10 °C
m l as
m .co
Number of divisions between those marks = 10
a g
a s eOne
gl
small division = 10/10 = 1 °C
a So the smallest value this thermometer can read = 1 °C
se m
com g l a
m . a
ase
Your school laboratory may have thermometers for which the range and the smallest division

agl
are different. So always look carefully at the thermometer you are about to use before you take
a reading.

. com VALUE
BETWEEN TWO BIG MARKS NUMBER OF DIVISIONS
em SMALLEST

m l as
.10co°C a g
sem
10 1 °C

a
agl 10 °C 20 0.5 °C
c
m .
a s e
com agl
10 °C 5 2 °C

.
m 10
e
las
5 °C 0.5 °C

ag

co m
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m ase
.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Activity 7.5: Let us measure — Page 132
Correct way of measuring temperature using a laboratory thermometer

ACTIVITY

Q1 What is the temperature of water measured by you? Compare it with the readings
of your friends.

Do it exactly as the book describes and then write down what your thermometer shows.

1. Take some warm water in a beaker.
2. Dip the thermometer so that the bulb is fully immersed in the water, but does not touch the
bottom or the sides.
3. Hold it vertically and watch the liquid column rise.
4. Wait until the column stops rising — but do not wait too long, or the water itself will begin
to cool.
5. Read the mark that the top of the liquid column touches, keeping your eye in line with it,
while the thermometer is still in the water.

✗ eye too high

Warm water

top of liquid column
✓ eye in line

bulb clear of the bottom
✗ eye too low

Reading a laboratory thermometer. The eye must be exactly in line with the top of the liquid column;
looking from above or from below gives a wrong reading. The bulb stays fully in the water but does
not touch the bottom or the sides.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Sample answer: “The temperature of the warm water measured by me was 45 °C.” Three
friends measuring the same beaker got 45 °C, 44 °C and 45 °C.

Why the readings differ a little: the water keeps cooling all the time, so a friend
who measured a minute later gets a slightly lower value. Also, the thermometer can
only be read to its smallest value — 1 °C for the usual laboratory thermometer — so
a true 44.6 °C will be written by one student as 45 °C and by another as 44 °C.

Q2 Do you notice that, as soon as you take the thermometer out of the water, the level
of liquid column begins to fall?

Yes. The moment the thermometer leaves the warm water, the liquid column starts sliding
down.

Why it happens: the liquid in the bulb expands when it is heated and contracts
when it cools. Out in the open the bulb begins losing heat to the cooler air at once,
the liquid contracts, and the column falls. A laboratory thermometer has no kink to
hold the liquid in place, so nothing stops it from running back into the bulb.

Therefore: the temperature must be read while the thermometer is still immersed in the water.

Tip: This is the one big difference from a clinical thermometer. A clinical
thermometer can be taken out and read at leisure, because the kink above its bulb
keeps the thread of mercury from slipping back.

In-text Questions — Page 132
Correct way of measuring temperature using a laboratory thermometer

Q1 Can we use a laboratory thermometer for measuring body temperature of a
person?

No, it should not be used for that. Here is why, point by point:

Page 26 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

POINT LABORATORY THERMOMETER CLINICAL THERMOMETER

Range –10 °C to 110 °C About 35 °C to 42 °C

Smallest value Usually 1 °C 0.1 °C

Holds the No kink — the column falls as soon as it is Kink holds the reading
reading? taken out

Shape and Long, straight, easily broken; not meant for Short, with a rounded bulb made for the
safety the mouth mouth or armpit

The deciding reason is the smallest value. A fever of 37.6 °C is a real fever, but a laboratory
thermometer that reads only to the nearest 1 °C would call it “38 °C” or “37 °C” — and the
reading would in any case begin to fall the instant the thermometer left the body.

More to do! — Page 133
Temperature of melting ice and of boiling water

MORE TO DO!

Q1 Following two experimental setups are to be arranged by your teacher. One by one,
as per your turn, go closer to the setups and observe the readings of both the
thermometers. What are the temperatures of ice and boiling water?

Read the two laboratory thermometers, keeping your eye in line with the top of each liquid
column.

SETUP WHAT THE THERMOMETER SHOWS

Crushed ice (melting) about 0 °C

Boiling water about 100 °C

These are the standard values at sea level. In your own classroom the boiling water may read a
little less than 100 °C.

Why boiling water may not reach 100 °C: water boils at 100 °C only under normal
air pressure at sea level. Higher up a hill the air pressure is lower and water boils at a
lower temperature. That is why Phiban and her classmates in Shillong — a hill town
— recorded about 98 °C for boiling water in Activity 7.6, not 100 °C.

Page 27 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Caution: This activity must be done strictly under the supervision of the teacher.
Do not touch the experimental setups.

Q2 Read the temperatures of ice and boiling water again after some time. Are the
temperatures same or have changed?

They are the same — the readings have not changed.

The temperature of water remains constant while it is boiling, even though the burner
keeps supplying heat.
The temperature of ice remains constant while it is melting, even though the room keeps
supplying heat.

Why it happens: during a change of state, the heat supplied is used up entirely in
changing water into steam, or ice into water. It is not used in raising the
temperature. So the thermometer holds steady until all the ice has melted, or until
all the water has boiled away.

Did you know? Because these two temperatures are so dependable, they were used
to mark the Celsius scale in the first place: 0 for melting ice and 100 for boiling water,
with the space between divided into 100 equal parts.

Activity 7.6: Let us compare — Page 133

Page 28 of 55

ase
Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

7.3.2 Laboratory thermometer
co m
e m.
m as
ACTIVITY

.co a g l
a s em the temperatures of boiling water recorded by different students (Table
gl
Compare
a
Q1
7.2).

co m
em . ag
NAME
g l as
TEMPERATURE OF BOILING WATER (IN °C)
a
Phiban 97.8

co m
em.
Shemphang 98.0

om g l as
.cOnestar a
sem
97.9

a
agl
Kloi 98.0

Bandarisha 98.1
m a s
em
.co agl
a s
gl classmates in Shillong.
Table 7.2, page 133 — Temperature of boiling water, as recorded by Phiban and her

a

co m
m .
m as e
l

. coreadings a g
se m
The five taken in Shillong were:

g l a
a NAME TEMPERATURE OF BOILING WATER (IN °C)

se m
com g l a
.
Phiban
a
97.8

m
Shemphang 98.0
gl ase
Onestar
a
97.9

co m
m .
e
Kloi 98.0

m l as
.co a g
em
Bandarisha 98.1

a s
agl Now compare them:
.c
s e m
m a
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g l as
a

co m
m .
m ase
.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Lowest reading = 97.8 °C (Phiban)

Highest reading = 98.1 °C (Bandarisha)

Spread = 98.1 °C – 97.8 °C = 0.3 °C
Sum = 97.8 + 98.0 + 97.9 + 98.0 + 98.1 = 489.8

Average = 489.8 ÷ 5 = 97.96 °C, that is about 98.0 °C

So all five readings agree closely — they differ by at most 0.3 °C — and they cluster around 98.0
°C. Two students (Shemphang and Kloi) got exactly the same value.

Q2 Why are there differences in their readings? Discuss the possible reasons amongst
yourselves.

As the book says, maybe the correct way of reading temperature was not followed by all
the students. The likely reasons are:

The eye was not in line with the top of the liquid column — looking from above or below
shifts the reading (this is the commonest mistake).
The thermometer was taken out of the water before reading, so the column had already
started to fall.
The bulb touched the bottom or the side of the vessel, so it measured the hot glass rather
than the water.
The reading was taken too early, before the liquid column stopped rising.
Each student can only read up to the smallest value of the thermometer, so a true 97.95 °C
gets written as 97.9 °C by one student and 98.0 °C by another.

Why the whole group is below 100 °C: that part is not a mistake. Shillong stands
high in the hills, where the air pressure is lower, so water there really does boil at
about 98 °C. The small differences within the group come from how it was measured;
the gap from 100 °C comes from where it was measured.

Tip: When several people measure the same thing, take the average. Here the
average, 97.96 °C, is a better answer than any single reading.

Activity 7.7: Let us analyse — Pages 134 & 135

Page 30 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

7.3.3 Air temperature

ACTIVITY

Q1 Read or listen to the weather reports for a place for 10 successive days. Record the
maximum and minimum air temperature for each day in Table 7.3. Analyse the data
in Table 7.3.

S.NO. DATE MAXIMUM AIR MINIMUM AIR
TEMPERATURE TEMPERATURE

1.

.

.

10.

Table 7.3, page 134 — Maximum and minimum air temperature. The table is printed
blank; fill in the readings of your own ten days.

Pick one place — your own town is best — and one source (newspaper, TV news or an internet
weather page). Use the same source every day, and note both figures in °C.
Sample answer (Jaipur, ten days in February — your own table will have your own place and
dates):

Page 31 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

S. NO. DATE MAXIMUM AIR TEMPERATURE MINIMUM AIR TEMPERATURE

1. 1 Feb 24 °C 10 °C

2. 2 Feb 25 °C 11 °C

3. 3 Feb 23 °C 9 °C

4. 4 Feb 26 °C 12 °C

5. 5 Feb 27 °C 13 °C

6. 6 Feb 25 °C 12 °C

7. 7 Feb 22 °C 8 °C

8. 8 Feb 24 °C 10 °C

9. 9 Feb 28 °C 14 °C

10. 10 Feb 29 °C 15 °C

Analysing this data:

Highest maximum = 29 °C (10 Feb); lowest maximum = 22 °C (7 Feb).
Highest minimum = 15 °C (10 Feb); lowest minimum = 8 °C (7 Feb).
The daily difference (maximum – minimum) stays around 13 °C to 14 °C.
Over the ten days both the maximum and the minimum are slowly rising — winter is giving
way to summer.

Tip: Draw the two columns as two lines on a graph, days along the bottom and
temperature in °C up the side. The rise and fall shows up at a glance.

Q2 Does the maximum and minimum temperature stay at the same level during these
days?

No. Both the maximum and the minimum temperature change from day to day.

Why it happens: weather depends on several factors at once — clouds, wind, rain,
humidity and how strongly the Sun shines. Because those factors change every day,
these temperatures usually vary every day too.

There is, however, a clear seasonal pattern behind the daily jumps:

Page 32 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

As we approach the summer season, the temperature rises.
During the winter season, it falls.

Did you know? Air temperature is an important weather parameter and is
monitored at weather stations all over the world. Along with other parameters, this
data is used for making weather forecasts. Anna Mani — the “Weather Woman of
India”, quoted at the start of this chapter — built many of the instruments India uses
for exactly this work.

Let us enhance our learning — Pages 137 to 140
Chapter exercises

LET US ENHANCE OUR LEARNING

Q1 The normal temperature of a healthy human being is close to _______ . (i) 98.6 °C (ii)
37.0 °C (iii) 32.0 °C (iv) 27.0 °C

Answer: (ii) 37.0 °C
Why the others are wrong:

(i) 98.6 °C — 98.6 is the correct number, but on the Fahrenheit scale. Written as 98.6 °C it
would be a temperature close to boiling water. Watch the unit.
(iii) 32.0 °C — far below the human range, which does not normally go below 35 °C.
(iv) 27.0 °C — this is a pleasant room temperature, not a body temperature.

Tip: 37.0 °C and 98.6 °F are the same temperature. The number changes with the
scale, so always write the unit — this question is testing exactly that.

Q2 37 °C is the same temperature as _______ . (i) 97.4 °F (ii) 97.6 °F (iii) 98.4 °F (iv) 98.6 °F

Answer: (iv) 98.6 °F
The book states it directly: a temperature measured as 37.0 °C on the Celsius scale is equivalent
to 98.6 °F on the Fahrenheit scale.
You can also check it with the conversion rule:

Page 33 of 55

as e
Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

co m
e m.
Temperature in °F = (9/5) × temperature in °C + 32
m l as
.co
= (9/5) × 37 + 32
m a g
l a se
g
= 9 × 37 ÷ 5 + 32
a= 333 ÷ 5 + 32

com
. ag
= 66.6 + 32
e m
= 98.6 °F
g l as
a

co m
m.
Did you know? On the Kelvin scale the same temperature is 37 + 273.15 = 310.15 K
— no degree sign with K.
m as e
.co a g l
se m
g l a
a Q3 Fill in the blanks: (i) The hotness or coldness of a system is determined by its _______ .

m a s
agl
(ii) The temperature of ice-cold water cannot be measured by a _______ thermometer.
(iii) The unit of temperature is degree _______ .
m.co
l a se
ANSWER a g

co mANSWER
.
BLANK

e m
m l as
.co a g
(i) The hotness or coldness of a system is determined by its … temperature

a s e(ii)mThe temperature of ice-cold water cannot be measured by a … thermometer
agl
clinical

(iii) The unit of temperature is degree … Celsius
se m
com g l a
m . a
ase
(i) Temperature is the reliable measure of hotness or coldness — touch is not.

a gl
(ii) Ice-cold water is at about 0 °C, well below the 35 °C at which a clinical thermometer’s scale
begins, so a clinical thermometer cannot measure it. A laboratory thermometer (–10 °C to 110
°C) can.
co m
m .
as e
(iii) On the Celsius scale the unit is degree Celsius (°C). (On the Fahrenheit scale it is degree
m
.co g l
Fahrenheit, °F; the SI unit, however, is the kelvin, K, which takes no degree sign.)
a
se m
g l a
a Tip: The book has a special note on writing units — “degree” starts with a small
c
letter, but “Celsius” and “Fahrenheit” start with capitals, and a space is left between
m .
m a s e
co agl
the number and the unit: 37.0 °C, not 37.0°C.

m .
as e
a g l

co m
m .
m ase
.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q4 The range of a laboratory thermometer is usually _______ . (i) 10 °C to 100 °C (ii) –10 °C
to 110 °C (iii) 32 °C to 45 °C (iv) 35 °C to 42 °C

Answer: (ii) –10 °C to 110 °C

Why this range: a laboratory thermometer must handle the whole of ordinary
laboratory work — ice at 0 °C, cold water below that, room air, warm water and
water boiling at about 100 °C. So the scale is carried a little below 0 °C and a little
above 100 °C, giving a total span of 110 – (–10) = 120 °C.

Why the others are wrong:

(i) 10 °C to 100 °C — could not measure ice, and could not quite reach boiling.
(iii) 32 °C to 45 °C and (iv) 35 °C to 42 °C — these are body-temperature ranges. (iv) in
particular is the range of a clinical thermometer.

Page 35 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q5 Four students used a laboratory thermometer to measure the temperature of
water as shown in Fig. 7.6.

Student 1 Student 2 Student 3 Student 4

Fig. 7.6, page 137 — redrawn sketch. Four students measuring the temperature of the
same water with a laboratory thermometer. Look at how each one holds the
thermometer and where the bulb sits.

Who do you think followed the correct way for measuring temperature? (i) Student
1 (ii) Student 2 (iii) Student 3 (iv) Student 4

Answer: (ii) Student 2
Looking carefully at each picture in Fig. 7.6:

STUDENT WHAT THE PICTURE SHOWS CORRECT?

Student 1 Thermometer held slanting, resting against the beaker with the ✗ Tilted, and the bulb touches
bulb at the bottom the beaker

Student 2 Thermometer vertical, bulb well inside the water, clear of the ✓ Correct
bottom and the sides

Student 3 Thermometer vertical, but the bulb rests on the bottom of the ✗ Bulb touching the bottom
beaker

Student 4 Thermometer leaning on the rim, bulb barely at the water ✗ Bulb not fully in the water
surface, not properly immersed

The book’s three rules for the correct way are all satisfied only by Student 2:

the bulb should not touch the bottom or the sides of the beaker;
the thermometer should be held vertically, not tilted;

Page 36 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

the temperature must be read while the thermometer is immersed in the water — and
while reading, the eye should be directly in line with the top of the liquid column.

✗ eye too high

Warm water

top of liquid column
✓ eye in line

bulb clear of the bottom
✗ eye too low

Reading a laboratory thermometer. The eye must be exactly in line with the top of the liquid column;
looking from above or from below gives a wrong reading. The bulb stays fully in the water but does
not touch the bottom or the sides.

Why touching the bottom is wrong: the bottom of the beaker may be hotter or
colder than the water itself. Resting the bulb there makes the thermometer measure
the glass, not the water.

Page 37 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q6 Colour to show the red column on the drawings of thermometers (Fig. 7.7) as per
the temperatures written below: 14 °C, 17 °C, 7.5 °C

30 30 30

14 °C 17 °C 7.5 °C
20 20 20

10 10 10

0 0 0

–10 –10 –10

Fig. 7.7, page 138 — three thermometers, all marked from –10 °C to 30 °C. Look carefully
— they are not divided alike. Colour each red column up to the temperature written
beside it.

First look at each scale, because the three thermometers of Fig. 7.7 are not divided alike. All
three are marked from –10 °C to 30 °C, but:

THERMOMETER DIVISIONS BETWEEN 0 °C ONE SMALL TEMPERATURE TO
AND 10 °C DIVISION COLOUR

First 5 2 °C 14 °C

Second 10 1 °C 17 °C

Third 20 0.5 °C 7.5 °C

Page 38 of 55

ase
Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

c om
Now colour the column red from the bulb up to the correct mark:

14 °C on the first thermometer — 2 divisions above the 10 °C mark (10 + 2 +e2m
.
m a s = 14).

. cosecond — 7 divisions above the 10 °C mark. a gl
m the third — 15 divisions above the 0 °C mark (15 × 0.5 = 7.5).
17 °C on the

a s eon
agl
7.5 °C

co m
. ag
1 division = 2 °C 1 division = 1 °C 1 division = 0.5 °C

em
30
g l as 30 30
a

. co20m
m
20 20

as e
om°C l
17 °C
.c14 a g
se m
g l a
a 10 10
7.5 °C
10

m a s
em
.co agl
s
0 0 0
l a
ag

co m –10
.
–10 –10

em
m l as
.co a g
a s em
gl
Answer to Question 6. The red column is filled up to 14 °C, 17 °C and 7.5 °C. The third scale can show
a 7.5 °C only because its smallest division is 0.5 °C.

se m
com g l a
m . a
ase
Why the three scales are different: the question is quietly teaching that a

a gl
temperature can only be shown on a thermometer whose smallest division allows it.
7.5 °C cannot be marked on the first thermometer at all — its marks jump 2 °C at a
time.
co m
m .
m as e
.co a g l
se m
g l a
a c
m .
m a s e
e m . co agl
g l as
a

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m .
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.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q7 Observe the part of thermometer shown in Fig. 7.8 and answer the following
questions:

–10 0 10 20 30 40

Fig. 7.8, page 138 — the part of the thermometer to observe. The numbered marks run
from –10 to 40, and the red column ends between two of them.

(i) What type of thermometer is it? (ii) What is the reading of the thermometer? (iii)
What is the smallest value that this thermometer can measure?

(i) It is a laboratory thermometer.
You can tell from the scale itself: it is marked from below 0 °C (the first label is –10) up past 40
°C. A clinical thermometer would begin at about 35 °C and stop at 42 °C, and would never show
negative temperatures.
(ii) The reading is 26 °C.

The red liquid column has crossed the 20 °C mark.

Count the small divisions past 20 °C: 21, 22, 23, 24, 25, 26 — the column ends at the sixth

one.

Reading = 26 °C

–10 0 10 20 30 40

26 °C

Fig. 7.8 redrawn. Ten small divisions fit between 0 °C and 10 °C, so one division = 1 °C. The red column
stops at the sixth mark after 20 °C — the reading is 26 °C.

Page 40 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

(iii) The smallest value it can measure is 1 °C.

Difference between two numbered marks (0 °C and 10 °C) = 10 °C

Number of small divisions between them = 10

One small division = 10 °C ÷ 10 = 1 °C

Tip: Always answer part (iii) before part (ii). Once you know that one division is 1 °C,
counting divisions gives the reading straight away.

Q8 A laboratory thermometer is not used to measure our body temperature. Give a
reason.

Reason: a laboratory thermometer has no kink above its bulb, so the liquid column begins to
fall the moment the thermometer is taken out of the mouth — the reading is lost before it can
be read.

Bulb
35 36 37 38 39 40 41 42 °C

Kink (constriction)
37.0 °C (normal)
stops mercury falling back

The older mercury clinical thermometer. Its scale covers only 35 °C to 42 °C — the range of human
body temperature. The kink just above the bulb stops the mercury from running back, so the reading
stays put after the thermometer is taken out. (On a real one each small division is 0.1 °C; only the 0.2
°C marks are drawn here.)

Any one of these is an acceptable reason; together they make the case complete:

No kink — the reading does not stay put, and a laboratory thermometer cannot be read
while it is inside the mouth.
Too coarse — its smallest value is usually 1 °C, while body temperature has to be known to
0.1 °C. A rise from 37.0 °C to 37.6 °C is a real fever, and a laboratory thermometer simply
cannot show it.

Page 41 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Wrong range for the job — its scale is spread over 120 °C (–10 °C to 110 °C), so the few
degrees that matter for the body are squeezed into a tiny part of the scale.
Shape and safety — it is long, straight and fragile, and is not designed to be put into a
person’s mouth or armpit.

How the kink solves this: the kink is a narrow constriction in the tube just above
the bulb. While the thermometer is warming, the expanding mercury is pushed past
it. When the thermometer is removed and the mercury cools and contracts, the
thread breaks at the kink, so the mercury above it cannot slide back — the reading
stays until you shake it down.

Q9 Vaishnavi has not gone to school as she is ill. Her mother has kept a record of her
body temperature for three days as shown in Table 7.4.

DAY TEMPERATURE AT

7AM 10AM 1PM 4PM 7PM 10PM

One 38.0 °C 37.8 °C 38.0 °C 38.0 °C 40.0 °C 39.0 °C

Two 38.6 °C 38.8 °C 39.0 °C 39.0 °C 39.0 °C 38.0 °C

Three 37.6 °C 37.4 °C 37.2 °C 37.0 °C 36.8 °C 36.6 °C

Table 7.4, page 139 — Body temperature record of Vaishnavi over three days.

(i) What was Vaishnavi’s highest recorded temperature? (ii) On which day and at
what time was Vaishnavi’s highest temperature recorded? (iii) On which day did
Vaishnavi’s temperature return to normal?

Table 7.4 again, with the highest value of each day marked:

DAY 7AM 10AM 1PM 4PM 7PM 10PM

One 38.0 °C 37.8 °C 38.0 °C 38.0 °C 40.0 °C 39.0 °C

Two 38.6 °C 38.8 °C 39.0 °C 39.0 °C 39.0 °C 38.0 °C

Three 37.6 °C 37.4 °C 37.2 °C 37.0 °C 36.8 °C 36.6 °C

Page 42 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

(i) The highest recorded temperature was 40.0 °C. Scanning all eighteen readings, the largest
is 40.0 °C; the next largest are the three readings of 39.0 °C on Day Two.
(ii) It was recorded on Day One at 7 pm.
(iii) On Day Three.

Normal body temperature = 37.0 °C

Day Three readings: 37.6 → 37.4 → 37.2 → 37.0 → 36.8 → 36.6 °C

The temperature comes down steadily and touches 37.0 °C at 4 pm, then stays at or below it.

So Vaishnavi’s temperature returned to normal on Day Three.

Reading the pattern: Day One and Day Two are the fever days — every reading is
above 38 °C except one. On Day Three not a single reading crosses 38 °C and the
whole day slopes downwards, which is how a fever settles.

Tip: Notice how much the temperature moves during a single day — 37.8 °C at 10
am and 40.0 °C at 7 pm on Day One. This is why a doctor asks for temperature to be
recorded several times a day, not once.

Page 43 of 55

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Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

co m
m.
If you have to measure the temperature 22.5 °C, which of the following three
e
Q10

m l as
.co
thermometers will you use (Fig. 7.9)? Explain.

a g
se m
g l a
a

com
e m . ag
as
30 30 30

a g l

m
.co
20 20 20

se m
com g l a
m . a
ase
agl
10 10 10

m a s
0
m.co 0 0
agl
l a se
ag

com
–10 –10 –10

m .
m ase
e m . co agl
g l as
a
(a) (b) (c)

Fig. 7.9, page 139 — three thermometers (a), (b) and (c). All three are marked from –10
se m
com g l a
. a
°C to 30 °C, but their small divisions are not of the same size.
m
ase
agl

com
Answer: thermometer (b).
m .
o m l a se
All three thermometers in Fig. 7.9 carry the same scale from –10 °C to 30 °C, so all three reach
.c °C. What differs is how finely each is divided. Counting the
a gsmall divisions between 0 °C and
m
se 10 °C on each:
22.5
a
agl c
m .
m a s e
e m . co agl
g l as
a

co m
m .
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.co


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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

THERMOMETER DIVISIONS BETWEEN 0 °C ONE SMALL CAN IT SHOW
AND 10 °C DIVISION 22.5 °C?

(a) 10 1 °C No — only 22 °C or
23 °C

(b) 20 0.5 °C Yes

(c) 5 2 °C No — only 22 °C or
24 °C

For (b): one small division = 10 °C ÷ 20 = 0.5 °C

22.5 °C = 20 °C + 5 divisions of 0.5 °C

So 22.5 °C falls exactly on a mark of thermometer (b).

Explanation to write: a thermometer can only be read to its smallest division. Thermometer (b)
has the finest divisions, 0.5 °C, and 22.5 °C lands exactly on one of its marks. On (a) 22.5 °C lies
halfway between two marks, and on (c) it lies between 22 °C and 24 °C — neither can show it
correctly.

Q11 The temperature shown by the thermometer in Fig. 7.10 is (i) 28.0 °C (ii) 27.5 °C (iii)
26.5 °C (iv) 25.3 °C

0 5 10 15 20 25 30 35 40

Fig. 7.10, page 140 — the thermometer scale. The numbered marks are 0, 5, 10 … 40,
and the red column ends past the 25 mark.

Answer: (ii) 27.5 °C
Work out the smallest value first, then count.

Page 45 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Numbered marks on Fig. 7.10: 0, 5, 10, 15, 20, 25, 30, 35, 40

Difference between two numbered marks = 5 °C

Small divisions between them = 10
One small division = 5 °C ÷ 10 = 0.5 °C

The red column ends past the 25 mark.

Divisions counted after 25: 25.5, 26.0, 26.5, 27.0, 27.5 — five divisions.

Reading = 25 °C + 5 × 0.5 °C = 27.5 °C

0 5 10 15 20 25 30 35 40

27.5 °C

Fig. 7.10 redrawn. Ten small divisions fit between 25 °C and 30 °C, so one division = 0.5 °C. The
column ends five divisions past 25 °C, that is at 27.5 °C.

Why the others are wrong: 28.0 °C is one division too far; 26.5 °C is two divisions short; and 25.3
°C could never be read at all on this thermometer, because 0.3 is not a multiple of its smallest
division of 0.5 °C.

Q12 A laboratory thermometer has 50 divisions between 0 °C and 100 °C. What does
each division of this thermometer measure?

Use the same rule as in Activity 7.4.

Page 46 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

One division = temperature difference ÷ number of divisions

Temperature difference = 100 °C – 0 °C = 100 °C

Number of divisions = 50

One division = 100 °C ÷ 50

= 2 °C

So each division of this thermometer measures 2 °C.

What that means: this thermometer is a coarse one. It can show 24 °C or 26 °C, but
never 25 °C — there is no mark there. Its smallest value is 2 °C.

Check it yourself: the usual laboratory thermometer of Fig. 7.3b has 10 divisions in
each 10 °C, giving 1 °C per division. To get 0.5 °C per division you would need 20
divisions in each 10 °C.

Q13 Draw the scale of a thermometer in which the smallest division reads 0.5 °C. You
may draw only the portion between 10 °C and 20 °C.

First decide how many divisions are needed.

Length of the portion to be drawn = 20 °C – 10 °C = 10 °C

Each smallest division must read 0.5 °C

Number of divisions = 10 °C ÷ 0.5 °C = 20 divisions

How to draw it:

1. Draw a straight line and mark two points on it, 10 cm apart. Label the left one 10 °C and the
right one 20 °C.
2. Divide the 10 cm into 20 equal parts — that is, put a mark every 5 mm. This gives 19 marks
in between, making 20 divisions in all.
3. Draw the marks at whole degrees (11, 12, 13 … 19) a little longer, and write the numbers
under them. The short marks in between stand for the half degrees 10.5, 11.5, 12.5 and so
on.
4. Each smallest division now reads 0.5 °C.

Page 47 of 55

Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

10 11 12 13 14 15 16 17 18 19 20

16.5 °C

Answer to Question 13 — the part of a scale between 10 °C and 20 °C, cut into 20 equal parts, so each
smallest division reads 0.5 °C. The column drawn here reads 16.5 °C.

Tip: Choose a length that divides easily. 10 cm for 10 °C is ideal, because every 0.5 °C
then becomes a neat 5 mm on your ruler.

Q14 Komal tells you that she has a fever of 101 degrees. Does she mean it on the
Celsius scale or Fahrenheit scale?

She means 101 degrees Fahrenheit, that is 101 °F — on the Fahrenheit scale.

Why it cannot be Celsius: the temperature of human beings does not normally go
below 35 °C or above 42 °C. A body temperature of 101 °C is impossible — water
itself boils at about 100 °C. So 101 has to be a Fahrenheit reading.

How high a fever is 101 °F? Compare it with normal:

Normal = 98.6 °F = 37.0 °C

Komal’s temperature = 101 °F

Rise above normal = 101 – 98.6 = 2.4 °F

In Celsius: (101 – 32) × 5/9 = 69 × 5 ÷ 9 = 345 ÷ 9 = 38.3 °C (rounded to one decimal place)

So Komal has a fever of about 38.3 °C — a moderate fever, about 1.3 °C above normal.

Page 48 of 55

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Class 6 Science Chapter 7 Temperature and its Measurement
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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Tip: If you visit a veterinary hospital, ask the doctor two things — what the normal
temperature of that animal is, and how much above normal counts as fever. Write
the answers in your notebook with the unit °C.

Q2 Find out which places in India are usually regarded to be the coldest and hottest.
Also, find out the minimum and the maximum temperatures recorded for these
places.

Usually regarded as the coldest:

Dras, in the Kargil district of Ladakh — often called the coldest inhabited place in India.
Temperatures near –45 °C have been recorded there.
The Siachen Glacier is colder still, but nobody lives there permanently.
Leh (Ladakh), Sela Pass (Arunachal Pradesh) and Keylong (Himachal Pradesh) are other very
cold places.

Usually regarded as the hottest:

Phalodi, in Rajasthan — where India’s highest reliably recorded temperature, about 51 °C,
was measured in May 2016.
Churu and Bikaner in Rajasthan, and Nagpur and Titlagarh (Odisha), regularly cross 47 °C
in summer.

Difference between the two extremes

= 51 °C – (–45 °C)

= 51 °C + 45 °C

= 96 °C — almost the whole range of a laboratory thermometer!

Check it yourself: Records change. Look up the India Meteorological Department
(IMD) website for the latest all-time maximum and minimum for these stations, and
note the date of each record along with the temperature.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q3 Various planets in our Solar System are at different distances from the Sun. Search
the Internet and make a table with the planets, their distances from the Sun (in
increasing order) and their temperatures written. Does the average temperature of
planets decrease as their distance from the Sun increases? If it is not true for any
planet, find out for which planet and why.

Here is the table, with the planets in increasing order of distance:

PLANET AVERAGE DISTANCE FROM THE SUN AVERAGE SURFACE TEMPERATURE

Mercury 58 million km about 167 °C

Venus 108 million km about 464 °C

Earth 150 million km about 15 °C

Mars 228 million km about –65 °C

Jupiter 778 million km about –110 °C

Saturn 1430 million km about –140 °C

Uranus 2870 million km about –195 °C

Neptune 4500 million km about –200 °C

Yes — as a general rule, the farther a planet is from the Sun, the colder it is. From Earth
outwards the temperature falls steadily, all the way to about –200 °C at Neptune.
But there is one clear exception: Venus. Venus is farther from the Sun than Mercury, yet it is
by far the hottest planet — about 464 °C against Mercury’s 167 °C.

Why Venus breaks the rule: Venus is wrapped in a thick atmosphere of carbon
dioxide. Sunlight gets in, warms the surface, but the heat cannot escape back into
space — the atmosphere traps it. This is the greenhouse effect, and on Venus it is
so strong that the planet stays hot enough to melt lead. Mercury, by contrast, has
almost no atmosphere, so all its heat escapes at night.

Did you know? Because it has no blanket of air, Mercury swings between roughly
430 °C in the day and –180 °C at night — the biggest temperature swing of any
planet in the Solar System.

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Q4 Hang a room thermometer in your classroom. Set up the apparatus, as shown in
Fig. 7.11, near the thermometer hung on the wall. Take the readings of
thermometers 1 and 2 three times during the day, say, first period, lunch break, and
last period. Record your readings. Compare the readings and draw your
conclusions. Repeat this for two weeks.

Thermometer 1
(Room thermometer)

Thermometer 2
(Laboratory thermometer)

Beaker

Water

Fig. 7.11, page 141 — set-up to measure the temperature of water and the room
temperature. Thermometer 1 is the room thermometer hung on the wall; Thermometer
2 is a laboratory thermometer clamped in a stand with its bulb dipped in a beaker of
water.

What to set up: Thermometer 1 is the room thermometer on the wall; Thermometer 2 is a
laboratory thermometer clamped in a stand with its bulb dipped in a beaker of water, standing
near the wall. Both must be read with the eye in line with the top of the column.
Sample record for one day (make a fresh row for each day, for two weeks):

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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

TIME OF DAY THERMOMETER 1 — ROOM THERMOMETER 2 — DIFFERENCE
AIR WATER

First period (8 am) 22 °C 23 °C 1 °C

Lunch break (12 29 °C 27 °C 2 °C
noon)

Last period (3 pm) 31 °C 29 °C 2 °C

Conclusions you can expect to draw:

Both temperatures rise from morning to afternoon and are highest in the last period,
because the Sun has been heating the building all day.
The water temperature follows the air temperature but lags behind it — it is a little higher
than the air in the cool morning and a little lower in the hot afternoon.
Over two weeks, days that felt hot show higher readings on both thermometers, so the water
is a fair, if slow, record of room temperature.

Why the water lags: water takes in and gives out a great deal of heat for every
degree it changes. So when the air warms quickly, the water has not caught up yet
— and when the air cools at night, the water is still holding yesterday’s warmth. This
is the same reason why places near the sea have milder weather than places inland.

Tip: Keep the beaker away from the window. Direct sunlight falling on it would heat
the water on its own and spoil the comparison.

Chapter at a glance
The temperature of a body is a reliable measure of how hot or cold it is. Our sense of
touch is not reliable — the same water in container B feels cool to a hand coming out of
warm water and warm to a hand coming out of ice-cold water.
A thermometer is the device that measures temperature. A clinical thermometer (today
usually a digital one) measures human body temperature; a laboratory thermometer is
used for everything else.
The three common scales are the Celsius scale (unit degree Celsius, °C), the Fahrenheit
scale (unit degree Fahrenheit, °F) and the Kelvin scale (unit kelvin, K). The SI unit of
temperature is kelvin, and temperature in K = temperature in °C + 273.15.
The normal temperature of a healthy human body is taken to be 37.0 °C, which is the same
as 98.6 °F. It is an average, so a perfectly healthy person may read a little above or below it.

Page 53 of 55

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Class 6 Science Chapter 7 Temperature and its Measurement
a g l AglaSem · NCERT Solutions

Human body temperature does not normally go below 35 °C or above 42 °C.
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Class 6 Science Chapter 7 Temperature and its Measurement AglaSem · NCERT Solutions

Quick revision

TERM WHAT IT MEANS KEY VALUE / UNIT WHERE IT
COMES IN THE
CHAPTER

Temperature A reliable measure of the hotness or SI unit: kelvin (K) Section 7.2, page
coldness of a body 125

Thermometer A device that measures temperature — Section 7.2, page
125

Clinical Thermometer used to measure human body Body range only, Section 7.3.1, page
thermometer temperature; today mostly digital about 35 °C to 42 °C 125

Laboratory Glass tube with a bulb of liquid (alcohol or Range –10 °C to 110 Section 7.3.2, page
thermometer mercury) and a Celsius scale, used for all °C 130
other purposes

Celsius scale The everyday temperature scale used on Unit: degree Celsius, Page 126
thermometers in India °C

Fahrenheit scale An older scale, still printed on some digital Unit: degree Page 128
thermometers Fahrenheit, °F

Kelvin scale The scale used in scientific work Unit: kelvin, K; K = °C Pages 128 and 129
+ 273.15

Normal body The average body temperature of a large 37.0 °C = 98.6 °F Page 128
temperature number of healthy people

Range of a From its lowest to its highest marked Lab thermometer: – Activity 7.3, page
thermometer temperature 10 °C to 110 °C 130

Smallest value (least The smallest temperature difference the Fig. 7.3b: 10 °C ÷ 10 Activity 7.4, page
count) thermometer can show = value between two = 1 °C 131
big marks ÷ number of divisions

Non-contact Measures body temperature without Used widely during Page 126
(infrared) touching the body COVID-19
thermometer

Absolute zero The lowest temperature that can be –273.15 °C = 0 K Page 141
achieved

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