Page 7 - NCERT Science Class 10 English Medium

You must have observed that magnesium ribbon burns with a
dazzling white flame and changes into a white powder. This powder is
magnesium oxide. It is formed due to the reaction between magnesium
and oxygen present in the air.

Activity 1.2
Activity
Activity 1.2 Activity 1.3
Activity 1.21.2
Activity 1.2
Activity 1.31.3
Activity 1.3
Activity
Activity 1.3
n Take lead nitrate n Take a few zinc granules in a conical flask or a test tube.
solution in a test n Add dilute hydrochloric acid or sulphuric acid to this
tube. (Fig. 1.2).
n Add potassium CAUTION: Handle the acid with care.
iodide solution n Do you observe anything happening around the zinc
to this. granules?
n What do you n Touch the conical flask or test tube. Is there any change in
observe? its temperature?
From the above three activities, we can say that any of
the following observations helps us to determine whether
a chemical reaction has taken place –
n change in state
n change in colour
n evolution of a gas
n change in temperature.
As we observe the changes around us, we can see
that there is a large variety of chemical reactions taking
place around us. We will study about the various types
of chemical reactions and their symbolic representation
in this Chapter.

1.1
1.1 CHEMICAL EQUA
CHEMICAL EQUATIONS
1.1 CHEMICAL EQUAAL EQUATIONSTIONS
1.1 CHEMICCHEMICAL EQUATIONSTIONS
1.1
Figure 1.2
Figure 1.2
Figure 1.2
Figure 1.2
Figure 1.2
Formation of hydrogen Activity 1.1 can be described as – when a magnesium ribbon is burnt in
gas by the action of
dilute sulphuric acid on oxygen, it gets converted to magnesium oxide. This description of a
zinc chemical reaction in a sentence form is quite long. It can be written in a
shorter form. The simplest way to do this is to write it in the form of a
word-equation.
The word-equation for the above reaction would be –
Magnesium + Oxygen → Magnesium oxide (1.1)
(Reactants) (Product)
The substances that undergo chemical change in the reaction (1.1),
magnesium and oxygen, are the reactants. The new substance is
magnesium oxide, formed during the reaction, as a product.
A word-equation shows change of reactants to products through an
arrow placed between them. The reactants are written on the left-hand
side (LHS) with a plus sign (+) between them. Similarly, products are
written on the right-hand side (RHS) with a plus sign (+) between them.
The arrowhead points towards the products, and shows the direction of
the reaction.

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