NCERT Class VII Science Solutions: Chapter 6-Physical and Chemical Changes Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 3:

Fill in the blanks in the following statements:

  1. When carbon dioxide is passed through lime water, it turns milky due to the formation of ________.
  2. The chemical name of baking soda is ________.
  3. Two methods by which rusting of iron can be prevented are ________ and ________.
  4. Changes in which only ________ properties of a substance change are called physical changes.
  5. Changes in which new substances are formed are called ________ changes.

Answer:

  1. When carbon dioxide is passed through lime water, it turns milky due to the formation of Calcium carbonate (CaCO3) .
As Showing in Images is a Result for Calcium Carbonate (CaCO …
  1. The chemical name of baking soda is Sodium bicarbonate (NaHCO3) .
As Showing in Images is a Sodium Bicarbonate (NaHCO3)
  1. Two methods by which rusting of iron can be prevented are greasing and galvanization.
As Showing in Images is a Greasing and Galvanization
  1. Changes in which only physical properties of a substance change are called physical changes.
  2. Changes in which new substances are formed are called chemical changes.

Question 4:

When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

Answer:

This a chemical change as new products are formed.

Baking soda + Lemon juice ⇾ Salt + Carbon dioxide + Water

When acid react with carbonates, salt is formed releasing carbon dioxide and water.