Question

E. Answer the following questions in detail.
1. When a candle burns, both physical and chemical change take place. How?
2. Setting of curd is a chemical change. Explain.
3. What do you observe when you mix vinegar and baking soda? How do you
perform a test for the evolving gas?
4. Describe how crystals of copper sulphate are prepared.
5. Which of the changes given below are chemical changes? Give reasons for your
answers.
a. Cutting grass b. Burning toast c. Making tea with a tea bag and water d. Frying an
egg e Combustion of petrol in a car f. Ironing of clothes g. Preparing custard from
milk h. Drying wet hair
6. An iron nail is taken to the moon. Another is kept near the Gateway of India,
Mumbai, while the third one is kept near the Red Fort, Delhi. Compare the degree
of rust formation on the three nails.
7. The liquified petroleum gas (LPG) is the gas which is used for cooking at home. In
the cylinder it comes as a liquid. When it comes out from the cylinder it become a
gas (Change A). Then it burns (Change B). What are the differences between change
A and B?
C
The decomposition of animal waste by anaerobic bacteria produces biogas
(Change A). The biogas is then burnt as fuel (Change B). What are the similarities
between the two changes.
Enhance Your Life Skills​

Answer 1

Answer:

1)because it can be reversed by cooling it. It is chemical change because it release carbon dioxide and many others gases

Answer 2

Explanation:

1. Because it can reverse by cooling.