EXERCISE

I.

1. Ans. Hydrogen

2. Ans. is corrosive

3. Ans. Carbonic acid.

4. Ans. Salt and water.

5. Ans. Weak acid.

II.

1. ✓

2. ×

3. ×

4. ✓

5. ✓

III. 

1. c.

2. e.

3. a.

4. b.

5. d.

IV.

1. 

Ans. Acids are compounds in which one of the elements that makes up a molecule is always the hydrogen element.

2.

Ans. Lemon and curd.

3.

Ans. Bases heav a soapy feel and bitter taste. Bases are compounds which contain oxygen oxygen with hydrogen.

4.

Ans. Sodium hydroxide and potassium hydroxide.

5. 

Ans. When an acid reacts with a base it produces salt and water and they neutralize each other.

6. 

Ans. A base that readily dissolves in water is known as alkali.

7.

Ans. A bee sting contains formic acid therefore it should be treated with a base to neutralize the acid.

V. Answer the following questions in two sentences.

1. 

Ans. Indicators substances which can be used to identify a given substance is an acid or base. Indicators are substances which changes colour when placed in acidic or basic conditions. 

Example: turmeric powder, bryophyllum leaves.

2.

Ans: When acids react with bases then salt and water is produced. This is called neutralisation reaction. In neutralisation reaction, the acid loses its acidity and the base its alkalinity.

3.

Ans: Different types of bacteria present in our mouth, they feed on the food particles that is left in our mouth. When the bacteria digest the food particles inside our mouth they release some acids. This acids can damage our tooth. Toothpaste being a base neutralises the weak acids and protect our teeth from damage.

4. 

Ans: Salt is a compound which is produced when acid and base reacts with each other. Some salts are available in nature they occur  naturally. Sea water is abundantly filled with table salt i.e. sodium chloride. Many other types of salts are found in earth crust. Some salts are man made. 

5. 

Ans: Normal rainwater is always slightly acidic because carbon dioxide from the air dissolves in water and forms mild carbonic acid.