NCERT Book Class 10 Science Chapter 1 Chemical Reactions and Equations

“Facts are not science — as the dictionary is not literature.”
Martin H. Fischer

CHAPTER 1
Chemical Reactions
and Equations

C onsider the following situations of daily life and think what happens
when –
n milk is left at room temperature during summers.
n an iron tawa/pan/nail is left exposed to humid atmosphere.
n grapes get fermented.
n food is cooked.
n food gets digested in our body.
n we respire.
In all the above situations, the nature and the identity of the initial
substance have somewhat changed. We have already learnt about physical
and chemical changes of matter in our previous classes. Whenever a chemical
change occurs, we can say that a chemical reaction has taken place.
You may perhaps be wondering as to what is actually meant by a
chemical reaction. How do we come to know that a chemical reaction
has taken place? Let us perform some activities to find the answer to
these questions.

Activity 1.1
CAUTION: This Activity needs
the teacher’s assistance. It
would be better if students
wear suitable eyeglasses.
n Clean a magnesium ribbon
about 3-4 cm long by rubbing
it with sandpaper.
n Hold it with a pair of tongs.
Burn it using a spirit lamp or
burner and collect the ash so
formed in a watch-glass as
shown in Fig. 1.1. Burn the
magnesium ribbon keeping it
away as far as possible from
your eyes. Figure 1.1
n What do you observe? Burning of a magnesium ribbon in air and collection of magnesium
oxide in a watch-glass