Acids and Bases

Samacheer Book Back Questions And Answers For Science Standard 8 “Acids and Bases“

I. Choose the best answer:
1. Acids are _____ in taste.
a) sour
b) sweet
c) bitter
d) salty

2. Aqueous solutions of _____ conduct electricity.
a) acid
b) base
c) salt
d) All of these

3. In acidic solutions blue litmus changes into _____ colour.
a) blue
b) green
c) red
d) white

4. Base is a substance that gives _____ on dissolving in water.
a) OH−
b) H+
c) OH
d) H

5. Sodium hydroxide is a _____.
a) acid
b) base
c) oxide
d) alkali

6. Red ant sting contains _____.
a) acetic acid
b) sulphuric acid
c) oxalic acid
d) formic acid

7. Magnesium hydroxides are used for treating _____.
a) acidity
b) head pain
c) teeth decay
d) None of these

8. Acid mixed with base forms _____.
a) salt and water
b) salt
c) water
d) No reaction

9. We brush our teeth with tooth paste because it is _____ in nature.
a) basic
b) acidic
c) Both a and b
d) None of these

10. In basic solution turmeric indicator paper changes from yellow to _____.
a) blue
b) green
c) yellow
d) red

II. Fill in the blanks:
1. Benzoic acids are used for _____.
2. The word sour refers to _____ in Latin.
3. Bases are _____ in taste.
4. Chemical formula of calcium oxide is _____.
5. Wasp sting contains _____.
6. Turmeric is used as a _____.
7. In acidic solution the colour of the hibiscus indicator paper will change to _____.

Answers:
1. preservation of food
2. acidus
3. bitter
4. CaO
5. alkaline substance
6. indicator
7. deep pink or deep red

III. State true or false. If false, correct the statement:
1. Most of the acids are not soluble in water.
2. Acids are bitter in taste.
3. Bases are soapy to touch when they are dry.
4. Acids are corrosive in nature.
5. All bases are alkalis.
6. Hibiscus flower is an example for natural indicator.

Answers:
1. True
2. False (Acids are sour in taste)
3. False (Bases are soapy to touch only in aqueous media, not in dry nature)
4. True
5. False (All alkalis are base, but all bases are not alkalis)
6. True

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