NCERT Class VIII Science Solutions: Chapter 4-Materials: Metals and Non-Metals Part 5

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Question 27:

Match the substances in Column A with their applications given in Column B.

Match the Column a and Column B.(Q)
Match the Column A and Column B.(Q)

Column A

(Substance)

Column B

(Application)

Oxygen

For making crackers

Copper

For disinfecting water

Sulphur

All living beings inhale during breathing

Iron

For making electric wires

Chlorine

For making rails

Answer:

Match the Column a and Column B.(A)
Match the Column A and Column B.(A)

Column A

(Substance)

Column B

(Application)

Oxygen

iii All living beings inhale during breathing

Copper

iv For making electric wires

Sulphur

i For making crackers

Iron

v For making rails

Chlorine

ii For disinfecting water

LONG ANSWER QUESTIONS

Question 28:

Some of the following statements are incorrect. Find the incorrect statements and correct them.

  1. The property of metals by virtue of which they can be drawn into wires is called ductility.

  2. Metals are good conductor of electricity but poor conductor of heat.

  3. Articles made of metals produce ringing sound when struck hard.

  4. Oxides of non-metals and metals are acidic in nature.

  5. A less reactive metal replaces a more reactive metal from its salt solution in water.

Answer:

Image of what is the conductor of electricity

What is the Conductor of Electricity

Image of what is the conductor of electricity

Statements (B), (D) and (E) are not correct.

(B) Metals are good conductor of electricity and also good conductor of heat.

(D) Oxides of non-metals are acidic in nature and oxides of metals are basic in nature.

(E) A more reactive metal replaces a less reactive metal from its salt solution in water.

Question 29:

Iron is more reactive than copper. Can you write an activity to show this?

Answer:

Take about 50 ml of water in a beaker and dissolved 5 g of copper sulphate in it to obtain copper sulphate solution. Put a clean iron nail in this solution and keep the beaker undisturbed for some time.

We will find that the blue color of copper sulphate solution starts fading gradually and the iron nail gets covered with a red brown layer of copper metal. It is because iron is more reactive than copper, so it displaces copper metal from its solution of copper sulphate.

It is the copper metal set free from its compound which forms a red brown layer on the surface of iron nail. This shows that iron is more reactive than copper.

Question 30:

Fill in the blanks to complete the following paragraph.

The name of the product formed in the reaction of Sulphur and _____________ is sulphur dioxide gas. When sulphur dioxide is dissolved in_________________, sulphurous acid is formed. The sulphurous acid turns _____________ litmus paper to ____________. Generally oxides of __________ are acidic in nature. After completing the paragraph write two questions which you can raise on the basis of this information.

Answer:

The name of the product formed in the reaction of sulphur and oxygen is sulphur dioxide gas. When sulphur dioxide is dissolved in water, sulphurous acid is formed. The sulphurous acid turns blue litmus paper to red. Generally oxides of non-metals are acidic in nature. After completing the paragraph write two questions which you can raise on the basis of this information.

  1. Which gas is formed when sulphur reacts with oxygen?

  2. What is the nature of oxides of non-metals?