9 - Chemical Reaction 

In this post, you can check the solutions to the exercises of Chemical Reaction of Oasis School Science Grade 9 by Jayananda Kapadi.

Group A

1. What is a physical change?
Answer: A change in which no new substance is formed is called a physical change. Such changes are reversible.

2. What is a chemical change?
Answer: A change in which new substance(s) is/are formed as the product is called a chemical change. Such changes are usually irreversible.

3. What is a chemical reaction?
Answer: The process of synthesis, analysis, or displacement of elements or compounds to produce products during a chemical change is called a chemical reaction.

4. What are 'reactants' and 'products'?
Answer: Reactants are the elements or compounds that undergo change during a chemical reaction. Products are the substance formed as the result of a chemical change.

5. What is a word equation?
Answer: A chemical reaction written by using the names of the reactants and products is called as a word equation.

6. What is a chemical (or formula) equation?
Answer: A chemical reaction written by using the symbols and molecular formulae of the reactant and products is called as a chemical (or formula) equation. 

7. Write any two pieces of information which can be obtained from a balanced chemical equation.
Answer: Following are the two pieces of information which can be obtained from a balanced chemical equation:
  1. The names and symbols of reactants and products
  2. The total number of atoms or molecules of reactants and products

8. Write any two limitations of a balanced chemical equation.
Answer: Following are the two limitations of a balanced chemical reaction:
  1. It gives no information about the physical state of the reactants and products.
  2. It doesn't give any information about the duration of the chemical reaction.
9. What is a catalyst?
Answer: A catalyst is a chemical substance that increases or decreases the rate of chemical reaction without getting involved in the reaction.

10. What type of catalyst is called a positive catalyst?
Answer: A catalyst that increases the rate of a chemical reaction is called a positive catalyst.

11. Define negative catalyst with one example.
Answer: A catalyst that decreases the rate of chemical reaction is defined as negative catalyst. Example: Glycerine.

12. Write any two characteristics of catalysts.
Answer: Following are the two characteristics of catalysts:
  1. It increases or decreases the rate of chemical reaction.
  2. It remains unchanged during a chemical reaction.

Group B

1. Melting of ice is called physical change but rusting of iron is called chemical change, why?
Answer: It is because during melting of ice, only the state changes which can again be reversed back. So, it is called a physical change. But, rusting of iron is called chemical change because a new product is formed which cannot be reversed back to iron.

2. Chemical equation should be balanced, why?
Answer: Sum of atomic masses of the reactants is always equal to that of the products. This is the law of conservation of mass. Due to this, chemical equation should be balanced.

3. Formula equation is more informative than word equation. Give reason.
Answer: It is because a formula equation tells us only about the reactants and products. However, a formula equation gives us information about the ratio of combining atoms.

About this book:

Oasis School Science Grade 10
Author: Jayananda Kapadi
Editor: Dr. Rameshwar Adhikari

About Oasis Publication:

Oasis Publication (P) Ltd.
Anamnagar, Kathmandu, Nepal
Phone: 0977-01-4224004