NCERT solutions for Class 7 Science chapter 6 - Physical and Chemical Changes [Latest edition]

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

Photosynthesis

Dissolving sugar in water

Burning of coal

Melting of wax

Beating aluminium to make aluminium foil

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.

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

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

Formation of manure from leaves is a physical change. (True/ False)

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

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

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

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

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

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

Fill in the blanks in the following statements:

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

Fill in the blanks in the following statements:

The chemical name of baking soda is _________.

Fill in the blanks in the following statements:

Two methods by which rusting of iron can be prevented are _________ and ____ _

Fill in the blanks in the following statements:

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

Fill in the blanks in the following statements:

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.

The gas we use in the kitchen is called liquefied petroleum gas (LPG). In the cylinder it exists as a liquid. When it comes out from the cylinder it becomes a gas (Change − A) then it burns (Change − B). The following statements pertain to these changes. Choose the correct one

Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.