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

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.

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.

(i) Process − A is a chemical change.

(ii) Process − B is a chemical change.

(iii) Both processes A and B are chemical changes.

(iv) None of these processes is a chemical change.