The rain containing excess of acid is called acid rain. The rain becomes acidic because carbon dioxide, sulphur dioxide and nitrogen dioxide which are present in the atmosphere mix with the rain to make it acidic.

Take some turmeric and mix it in some water to make a paste. Deposit it on blotting paper of filter paper and dry it. Cut thin strips of the yellow paper so obtained. These thin strips are turmeric paper

To prepare lime water, dissolve some lime in water in a bottle. Stir the solution and keep it for some time. Pour a little more water from the top. This is lime water

Vegetable stain is due to turmeric which gives reddish brown colour with base (presence of soap solution).

Stomach contains hydrochloric acid

Each cell of our body contains deoxyribonucleic acid (DNA).

When a metal oxide is dissolved in water, a base is formed e.g., sodium oxide (Na₂O) in water gives sodium hydroxide. These are called alkalies.

The effect of an ant bite can be neutralised by rubbing moist baking soda.

Carbonic acid.

(i) Baking soda
(ii) Soap or detergent

When hydrochloric acid reacts with sodium hydroxide solution, then sodium chloride salt is formed.

Milk of magnesia which contains magnesium hydroxide (base) is used to neutralise the effect of excessive acid in stomach.

The citric acid in lemon juice and oxalic acid in tomato.

(i) Turmeric
(ii) China rose

Acids turn blue litmus paper red while bases turn red litmus paper blue.