NCERT Solutions for Class 7 Term_policy Chapter 6 Physical And Chemical Changes

Classify the changes involved in the following processes as physical or chemical changes:

(a) Photosynthesis

(b) Dissolving sugar in water

(c) Burning of coal

(d) Melting of wax

(e) Beating aluminium to make aluminium foil

(f) Digestion of food

State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.

(a) Cutting a log of wood into pieces is a chemical change. (True/False)

(b) Formation of manure from leaves is a physical change.

(True/ False)

(c) Iron pipes coated with zinc do not get rusted easily. (True/False)

(d) Iron and rust are the same substances. (True/False)

(e) Condensation of steam is not a chemical change. (True/False)

Fill in the blanks in the following statements:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _________.

(b) The chemical name of baking soda is _________.

(c) Two methods by which rusting of iron can be prevented are _________ and

____ ____.

(d) Changes in which only _____ __ properties of a substance change are called physical changes.

(e) Changes in which new substances are formed are called _________changes.

When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.

How would you show that setting of curd is a chemical change?

Explain why burning of wood and cutting it into small piece are considered as two different types of changes.

Describe how crystals of copper sulphate are prepared.

Explain how painting of an iron gate prevents it from rusting.

Explain why rusting of iron objects is faster in coastal areas than in deserts.