NCERT Solutions For Class 8 Science Materials Metals and Non Metals

Class 8 Science Chapter 4 Question Answer:

Q1. Which of the following can be beaten into thin sheets?

(a) Zinc

(b) Phosphorus

(c) Sulphur

(d) Oxygen

Answer:

(a) Zinc. It is a metal and can be beaten into sheets because metals are malleable.

Rest three options are non-metals which are not malleable.

NCERT Solutions for Class 8 Science Chapter 4

Q2. Which of the following statements is correct?

(a) All metals are ductile.

(b) All non-metals are ductile.

(c) Generally, metals are ductile.

(d) Some non-metals are ductile.

Answer:

(c) Generally, metals are ductile. - Correct

Metals like sodium and potassium are soft and can be broken into pieces. They cannot be drawn into wires and hence are not ductile.

Materials Metals and Non Metals Class 8 Solutions

Q3. Fill in the blanks.

(a) Phosphorus is a very _________ non-metal.

(b) Metals are________ conductors of heat and ________ .

(c) Iron is__________ reactive than copper.

(d) Metals react with acids to produce________ gas.

Answer:

(a) Phosphorus is a very reactive non-metal.

(b) Metals are good conductors of heat and electricity.

(c) Iron is more reactive than copper.

(d) Metals react with acids to produce hydrogen gas.

Materials Metals and Non Metals Class 8 NCERT Solutions

Q4. Mark ‘T’ if the statement is true and ‘F’ if it is false.

(a) Generally, non-metals react with acids.

(b) Sodium is a very reactive metal.

(c) Copper displaces zinc from zinc sulphate solution.

(d) Coal can be drawn into wires.

Answer:

(a) Generally, non-metals react with acids. (F)

-Non-metals do not react with acids (because they cannot donate an electron to hydrogen ion).

(b) Sodium is a very reactive metal. (T)

-Sodium reacts with water to liberate heat. That is why it is kept in kerosene.

(c) Copper displaces zinc from zinc sulphate solution. (F)

-Zinc is more reactive than copper. Hence, copper cannot displace zinc.

(d) Coal can be drawn into wires. (F)

- Coal is very brittle and breaks when force is applied.

Class 8 Science Chapter 4 Question Answer

Q5. Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of these properties.

Answer:

Class 8 Science Chapter 4 NCERT Solutions

Q6 (a). Give reasons for the following.

Aluminium foils are used to wrap food items.

Answer:

Aluminium is malleable and hence can be beaten into thin sheets known as foils. Hence it is used to wrap food items.

NCERT Solutions for Class 8 Science Chapter 4:

Q6 (b). Give reasons for the following.

Immersion rods for heating liquids are made up of metallic substances.

Answer:

Metals are a very good conductor of heat. Hence immersion rods for heating liquids are made up of metallic substances to transfer heat to the liquid.

Materials Metals and Non Metals Class 8 Solutions:

Q6 (c). Give reasons for the following.

Copper cannot displace zinc from its salt solution.

Answer:

A higher reactive metal can displace less reactive metal from its aqueous salt solution. Hence, copper being less reactive than zinc, cannot replace it from a zinc sulphate solution.

Materials Metals and Non Metals Class 8 NCERT Solutions:

Q6 (d). Give reasons for the following.

Sodium and potassium are stored in kerosene.

Answer:

Sodium and potassium are very reactive metals and readily catches fire in the air. They cannot be kept in water as they react exothermically in water. Therefore they are stored in kerosene.

Class 8 Science Chapter 4 NCERT Solutions:

Q7. Can you store lemon pickle in an aluminium utensil? Explain.

Answer:

Lemon contains a mild acid known as citric acid. We know that metal reacts with an acid to liberate hydrogen gas. Hence lemon pickle can't be kept in an aluminium (a metal) utensil as it will react with citric acid to liberate hydrogen.

Class 8 Materials Metals and Non Metals NCERT Solutions

Q8. Match the substances given in Column A with their uses given in Column B.

Answer:

Materials Metals and Non Metals Class 8 Questions and Answers

Q9 (a). What happens when

Dilute sulphuric acid is poured on a copper plate?

Write word equations of the reactions involved.

Answer:

When dilute sulphuric acid is poured on a copper plate, bubbles of hydrogen gas forms on the plate. This is because copper is metal and metal reacts with an acid to liberate hydrogen gas.

Equation:

$\\ Cu\ (m) +\ H_{2}SO_{4}\ (aq)\ \rightarrow\ CuSO_{4}\ (l)\ \ \ +\ \ \ H_{2}\ (g) \\ Copper+\ \ Sulphuric\ acid \ \rightarrow Copper\ Sulphate+\ \ Hydrogen\ gas$

Class 8 Materials Metals and Non Metals NCERT Solutions:

Q9 (b). What happens when

Iron nails are placed in copper sulphate solution?

Write word equations of the reactions involved.

Answer:

We know that a more reactive metal displaces a less reactive metal from its salt solution. When iron nails are placed in copper sulphate solution, iron being more reactive than copper, displaces copper and forms ferrous(iron) sulphate salt and copper deposits on the iron nails. The blue colour solution turns into green.

$\\ Fe\ (m) +\ CuSO_{4}\ (aq)\ \rightarrow\ FeSO_{4}\ (aq)\ \ \ +\ \ \ Cu\ (m) \\ Iron+\ \ \ \ Copper\ Sulphate\rightarrow \ \ \ Ferrous\ Sulphate+\ \ Copper$

Class 8 Science Ch 4 Question Answer

Q10 (a). Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.

How will she find the nature of the gas?

Answer:

After burning the charcoal and collecting the gas evolved in the test tube, add a few drops of water in the test tube. Cover the test tube and shake it well. Then put a few drops of the solution on blue litmus paper and red litmus paper. If the blue litmus turns red, the nature of the gas is acidic. But if the red litmus turns blue, the gas is basic.

Materials Metals and Non Metals Class 8 Questions and Answers:

Q10 (b). Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.

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

Answer:

The reactions are as follows:

(i) Charcoal reacts with oxygen to form carbon dioxide gas.

$\\ \ \ C\ (s)\ \ \ \ \ \ \ + O_{2}\ (g) \ \ \ \rightarrow\ \ \ \ CO_{2}\ (g) \\Carbon\ \ \ \ \ \ Oxygen\ \ \ \ \ \ \ \ \ Carbon\ Dioxide \\\ _{from\ Charcoal}$

(ii) Carbon dioxide reacts with water to form carbonic acid, hence acidic in nature

$\\ CO_{2}\(g) \ \ \ \ \ \ \ \ \ \ \ + H_{2}O\ (l)\ \ \ \rightarrow\ \ \ H_{2}CO_{3}\(aq) \\ Carbon\ Dioxide\ \ \ \ Water\ \ \ \ \ \ \ Carbonic\ Acid$

Class 8 Chapter 4 Science Solutions:

Q11. One day Reeta went to a jeweller’s shop with her mother. Her mother gave an 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:

Aqua regia (mixture of HCl and $HNO_{3}$ in the ratio 3:1) is used to polish gold ornaments. When dipped in the liquid, the gold layer starts dissolving which causes a reduction in the weight. The outer unpolished layer dissolves and the layer becomes shiny.