NCERT Class VII Science Solutions: Chapter 5-Acids, Bases and Salts Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 18:

Match the substances in Column I with those in Column II.

Match the Substances in Column I with Those in Column II (Q)
Column IColumn II
  1. Tartaric acid
  • Soap
  • Calcium hydroxide
  • Curd
  • Formic acid
  • Unripe mangoes
  • Sodium hydroxide
  • Ant՚s sting
  • Lactic acid
  • Lime water

Answer:

Match the Substances in Column I with Those in Column II (A)
Column IColumn II
  1. Tartaric acid
iii. Unripe mangoes
  1. Calcium hydroxide
v. Lime water
  1. Formic acid
iv. Ant՚s sting
  1. Sodium hydroxide
i. Soap
  1. Lactic acid
Ii. Curd

Question 19:

Fill the blanks in the following sentences

  1. Lemon juice and vinegar taste ________contain________.
  2. Turmeric and litmus are ________ acid-base Indicators.
  3. Phenolphthalein gives ________ colour with lime water.
  4. When an acidic solution is mixed with a basic solution, they ________ each other forming ________ and water.

Answer:

  1. Lemon juice and vinegar taste sour contain acids.
  2. Turmeric and litmus are natural acid-base Indicators.
  3. Phenolphthalein gives pink colour with lime water.
  4. When an acidic solution is mixed with a basic solution, they neutralize each other forming salt and water.

LONG ANSWER QUESTIONS

Question 20:

Boojho, Paheli and their friend Golu were provided with a test tube each containing China rose solution which was pink in colour. Boojho added two drops of solution ‘A’ in his test tube and got dark pink colour. Paheli added 2 drops of solution ‘B’ to her test tube and got green colour. Golu added 2 drops of solution ‘C’ but could not get any change in colour. Suggest the possible cause for the variation in their results.

Answer:

‘A’ is an acidic solution.

‘B’ is a basic solution.

‘C’ is a neutral solution.

Question 21:

Fill in the cross word given as Figure with the help of the clues provided.

As Showing in Images is a Fill in the Cross Word (Q)

Across:

(2) The solution which does not change the colour of either red or blue litmus.

(4) Phenolphthalein gives pink colour in this type of solution.

(7) Colour of blue litmus in lemon juice.

Down:

(1) It is used to test whether a substance is acidic or basic.

(3) It is a natural indicator and gives pink colour in basic solution.

(5) Nature of ant՚s sting.

(6) It is responsible for increase in temperature during a neutralization reaction.

Answer:

As Showing in Images is a Fill in the Cross Word (A)

Across:

(2) The solution which does not change the colour of either red or blue litmus - Nautral

(4) Phenolphthalein gives pink colour in this type of solution - Base

(7) Colour of blue litmus in lemon juice - Red

Down:

(1) It is used to test whether a substance is acidic or basic - Indicator

(3) It is a natural indicator and gives pink colour in basic solution - Turmeric

(5) Nature of ant՚s sting -Acidic

(6) It is responsible for increase in temperature during a neutralization reaction - Heat