Samacheer Kalvi 8th Science Book Back Answers Chapter 14

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Samacheer Kalvi 8th Science Book Back Question and Answers:

Samacheer Kalvi 8th Standard Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2022 to 2023 Book Back Questions & Answers/solutions available for both English and Tamil Medium. Class 8 std Science Book Chapter 14 – Acids and Bases Science Answers/Solutions Guide are uploaded on this page. 8th standard Science Book is consists of 23 Units. All 23 chapters of Science Book Back One, and Two Mark Solutions are given below.

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8th Science Book Back Chapter 14 Solutions Guide PDF:

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8th Science Chapter – 14

Acids and Bases – Book Back Answers

 

I. Choose the best answer:

1. Acids are ……………. in taste.
(a) sour
(b) sweet
(c) bitter
(d) salty
Answer:
(a) sour

2. Aqueous solutions of ……………. conduct electricity.
(a) acid
(b) base
(c) salt
(d) salt and base
Answer:
(d) salt and base

3. In acidic solution, blue litmus changes into ……………. colour.
(a) blue
(b) green
(c) red
(d) white
Answer:
(c) red

4. Base is a substance that gives ……………. on dissolving in water.
(a) OH–
(b) H+
(c) OH
(d) H
Answer:
(a) OH

5. Sodium hydroxide is a …………….
(a) acid
(b) base
(c) oxide
(d) alkali
Answer:
(d) alkali

6. Red ant sting contains …………….
(a) acetic acid
(b sulphuric acid
(c) oxalic acid
(d) formic acid
Answer:
(d) formic acid

7. Magnesium oxides are used for treating …………….
(a) acidity
(b) head pain
(c) teeth decay
(d) None of these
Answer:
(a) acidity

8. Acid mixed with base forms …………….
(a) salt and water
(b) salt
(c) water
(d) no reaction
Answer:
(a) salt and water

9. We brush our teeth with tooth paste because it is …………….
(a) basic
(b) acidic
(c) both a and b
(d) none of these
Answer:
(a) basic

10. In basic solution turmeric indicator paper changes from yellow to …………….
(a) blue
(b) green
(c) yellow
(d) red
Answer:
(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 formulae 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 …………

Answer:

  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.
Answer:
True.

2. Acids are bitter in taste.
Answer:
False
Correct statement:
Acids are sour in taste. Bases are bitter in taste.

3. Bases are soapy to touch when they are dry.
Answer:
False
Correct statement:
Bases are soapy to touch only in aqueous media, not in dry nature.

4. Acids are corrosive in nature.
Answer:
True

5. All bases are alkalis.
Answer:
False
Correct statement:
All alkalis are base, but all bases are not alkalis.

6. Hibiscus flower is an example for natural indicator.
Answer:
True

IV. Answer briefly:

1. Define acid.
Answer:
A substance which contains one or more replaceable hydrogen atoms.

2. Write any four physical properties of acids.
Answer:

  1. Acids are sour in taste.
  2. They are corrosive in nature. Strong acids can spoil substances like human skin, clothes and paper.
  3. Generally acids exist in liquid state but few acids exist in solid state too. E.g. Benzoic acid.
  4. Acids are colourless.
  5. Acids change the colour of the indicators. Blue litmus paper turns red and methyl orange turns pink when treated with acids.

3. What are the similarities between acids and bases?
Answer:

  1. They are corrosive in nature.
  2. They undergo ionization in aqueous solution.
  3. They conduct electricity in aqueous solution.
  4. They undergo neutralization reaction.

4. State the difference between acids and bases.
Answer:
Acids:

  1. They produce H+ions in water.
  2. They are sour in taste.
  3. Few acids are in solid state.
  4. Acids turn blue litmus paper red.

Bases:

  1. They produce OH–ions in water.
  2. They are bitter in taste.
  3. Most of the bases are in solid state.
  4. Bases turn red litmus paper blue.

5. What is an indicator?
Answer:
An indicator or acid – base indicator is a chemical substance which indicates the acidic or basic nature of a solution by suitable colour change.

6. What is a neutralization reaction?
Answer:
Neutralization is a chemical reaction in which an acid and a base react with each other to form water and salt.

7. Write any four physical properties of base.
Answer:

  1. Bases generally exist in solid state but some bases exist in liquid state also. E.g. Ammonium hydroxide, calcium hydroxide.
  2. Bases give soapy touch only in aqueous media not in dry nature.
  3. Bases are bitter in taste.
  4. Bases are corrosive in nature. When come in contact with the skin frequently they form painful blisters.
  5. Bases also change the colour of the indicators. Red litmus paper turns blue when . treated with bases. Similarly, they turn methyl orange yellow and phenolphthalein pink.

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