Page 79 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

Let us assess

1. Classify the following into elements and compounds.
Ammonia, sugar, nitrogen, mercury, sodium chloride, water,
copper sulphate, sodium, carbon.
2. Analyse the chemical equation given for the reaction between
nitrogen and hydrogen to give ammonia.

N + 3H 2NH
2 2 3
(a) What are the reactants and products in this reaction?
(b) Find the total number of molecules and atoms of the
reactants.

(c) Find the total number of molecules and atoms of the
products.
(d) What is the relation between the number of atoms of the
reactants and products?

3. N is the symbol of nitrogen.
(a) What do N , 2N and 2N indicate?
2 2
(b) How many molecules and atoms are present in 5N ?
2
4. Some chemical equations are given.

C+ O CO
2 2
CH + 2O CO + 2H O
4 2 2 2
N + O NO
2 2
CaCO CaO + CO
3 2
H + I HI
2 2
Fe + HCl FeCl +H
2 2
CO + C CO
2
(a) Which of these are balanced chemical equations?

(b) Balance those equations which are not balanced.
5. Find whether the following statements are right or wrong.
(a) All atoms of the same element show the same properties.

(b) The atoms present in a compound are different.
(c) Elements are pure substances.

(d) Hydrogen is a monoatomic molecule.

Basic Science VIII
78 78 Basic Science VIII