NCERT Class VIII Science Solutions: Chapter 4-Materials: Metals and Non-Metals Part 4

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Question 9:

What happens when?

  1. Dilute sulphuric acid is poured on a copper plate?

  2. Iron nails are placed in copper sulphate solution?

Write word equations of the reactions involved.

Answer:

  1. Copper does not react with dilute sulphuric acid. When concentrated sulphuric acid is poured on a copper plate, copper reacts with sulphuric acid to liberate hydrogen gas.

  1. The reactivity of iron is more than copper. So, iron will displace copper from copper sulphate solution. In this reaction, the blue colour of copper sulphate fades.

Question 10:

Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.

  1. How will she find the nature of the gas?

  2. Write down word equations of all the reactions taking place in this process.

Answer:

  1. Add some water in the test tube in which gas is collected. Now, cover the test tube. Shake it well. Test the solution with blue litmus and red litmus. Blue litmus turns red. Thus, the nature of gas is acidic.

  2. Charcoal when reacts with oxygen forms carbon dioxide gas

Image result for burning charcoal and collected the gas

Burning Charcoal and Collected the Gas

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Question 11:

One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

Answer:

To polish a gold ornament, it is dipped in an acid (called Aqua Regia). The outer layer of gold dissolves in the acid and the inner shiny layer is visible. Because of loss of upper layer of jewellery, its weight is reduced.