Match the statements in column A with those in column B. Column A Column B 1. A substance which turns turmeric solution reddish brown. (a) Base 2. A reaction between an acid and a base. (b) Acetic acid 3. An acid present in the vinegar. (c) Neutralisation 4. An indicator derived from the lichen. (d) Ant 5. An insect whose sting contains formic acid. (e) Litmus

A substance that turns turmeric solution reddish brown is a base. Turmeric is a natural indicator. Turmeric is yellow in acid and neutral substances, but turns reddish brown in basic medium. A reaction between an acid and a base is called neutralisation. This reaction gives salt and water. The acid present in vinegar is acetic acid. Acetic acid is a weak organic acid. Its chemical formula is CH 3 COOH . Vinegar is applied to cure wasp bite. An indicator derived from lichen is litmus. Litmus is used to test whether a substance is acidic or basic. The acidity or alkalinity of a solution is determined by the concentration of hydrogen ions, expressed as a pH value. An insect whose sting contains formic acid is an ant. The stings of ants and bees contain formic acid. When these insects sting, they inject formic acid in our body which causes a painful irritation and swelling. It can be cured by applying a base such as soap solution or calamine. Column A Column B 1. A substance which turns turmeric solution reddish brown. (a) Base 2. A reaction between an acid and a base. (c) Neutralisation 3. An acid present in the vinegar (b) Acetic acid 4. An indicator derived from the lichen. (e) Litmus 5. An insect whose sting contains formic acid. (d) Ant

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q IV

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Most of the fruits contain organic acids.

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Important Questions on Acids, Bases and Salts

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q V

Match the statements in column A with those in column B.

Column A	Column B
1. A substance which turns turmeric solution reddish brown.	(a) Base
2. A reaction between an acid and a base.	(b) Acetic acid
3. An acid present in the vinegar.	(c) Neutralisation
4. An indicator derived from the lichen.	(d) Ant
5. An insect whose sting contains formic acid.	(e) Litmus

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q VI

Name three organic and three inorganic acids.

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q VI

What are indicators? Name any three indicators and state the colour change which takes place in (i) acids (ii) bases.

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q VI

What are neutral substances? Give examples of two neutral substances.

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q VI

You are given three unlabelled bottles A, B and C containing colourless solutions, such that one of them is acid, the other base and the third neutral. How will you distinguish between them by using china rose as an indicator?

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q VI

What do you understand by the term neutralisation? Describe an activity in which neutralisation of hydrochloric acid takes place with sodium hydroxide, using phenolphthalein as an indicator.

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q VI

Explain why Farmers add slaked lime to acidic soils?

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Learning Elementary Science for Class 7>Chapter 5 - Acids, Bases and Salts>EXERCISES>Q VI

Explain why soap solution or baking soda paste is applied on the part of the body stung by a bee?