NCERT Solutions for Class 8 Science Chapter 4 - Metal and Non-Metal


Why is gold jewellery so popular?

How can you make jewellery from it?

Metals are important to human civilisation. We use them in various ways in our everyday life. The plates we eat in to our phones, all are made from some type of metal. Similarly non-metals like Oxygen, Phosphorous, Chlorine etc are important to our survival. They all possess certain properties which allow us to make use of them in various ways.

This chapter highlights the metals and non-metals around us and how to distinguish them. This chapter also provides a detailed discussion of the physical and chemical properties of metal and non-metals.


✍ Download PDF of Class 8 Science Chapter 4 Solutions


Question 1. Which of the following can be beaten into thin sheets?

(a) Zinc

(b) Phosphorus

(c) Sulphur

(d) Oxygen

Solution: (a) Zinc

We can beat metals into thin sheets but cannot do the same with the case of non-metals. Zinc being a metal can be beaten into a thin sheet. Phosphorous and sulphur are solid non-metals. They are brittle. So, they break on beating with a hammer. Oxygen is a gaseous non-metal. It is impossible to break it with a hammer.


Question 2. 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.

Solution: (c) Generally, metals are ductile.

Metals are ductile but not all of them. Some metals like mercury and tungsten cannot be beaten into wires.

Non-metals aren't ductile in any way. They are brittle. They are not suitable for making wires.


Question 3. 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.

Solution:

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

Phosphorous is highly reactive. It reacts with atmospheric oxygen when left exposed to air and start igniting.

(b) Metals are conductors of heat and electricity.

Metals allow heat and electricity to pass through them. So, they are conductors.

(c) Iron is more reactive than copper.

Iron is above the copper in the reactivity series. It can displace copper in a chemical reaction. Due to this, iron is more reactive than copper.

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

The reaction of metals with acids gives metal salts and hydrogen gas.


Question 4. 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. ( )

Solution:

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

Non-metals generally do not react with acids. Some of the exceptions are silicon and sulphur.

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

Sodium is a highly reactive metal. It reacts immediately with air to produce heat and light. So, it is kept in kerosene oil so as to prevent its exposure to air.

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

Copper is less reactive than zinc. It is below zinc in the reactivity series. So, it cannot displace zinc from zinc sulphate solution.

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

Coal is a non-metal. The ductility property is not shown by non-metals. So, coal is non-ductile.


Question 5. Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.

class 8 science chapter 4 question 5

Solution:

Properties

Metals

Non-metals

1. Appearance

Lustrous

Dull

2. Hardness

Hard

Soft

3. Malleability

Have property of Malleability

Do not have a property of Malleability

4. Ductility

Have property of Ductility

Do not have the property of Ductility

5. Heat Conduction

Good conductor of Heat

Bad Conductor of Heat

6. Conduction of Electricity

Good conductor of Electricity

The bad conductor of Electricity

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Question 6. Give reasons for the following.

(a) Aluminium foils are used to wrap food items.

We use aluminium to wrap food. This is because aluminium being a metal is malleable. We can use a hammer to convert it into a thin sheet. Secondly, it is less reactive. It does not react with food items and does not alter their taste.

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

For making immersion rods, we need material that can transfer heat so that the liquid gets heated up. So, we use metals to make such rods.

(c) Copper cannot displace zinc from its salt solution.

Copper is less reactive than zinc. It cannot displace zinc from its salt solution.

(d) Sodium and potassium are stored in kerosene.

Sodium and potassium are highly reactive metals. When they come in contact with atmospheric oxygen, they burst out into flames and heat energy. To avoid oxygen contact, these metals are kept in kerosene.


Question 7. Can you store lemon pickle in an aluminium utensil? Explain.

Solution: Aluminium is a metal. Lemon pickle contains an acid. Metals react with acids to form salt and hydrogen. If we keep lemon pickle in an aluminium utensil, the lemon reacts with aluminium and the pickle gets spoiled.


Question 8. Match the substances given in Column A with their uses given in Column B.

A

B

(i) Gold

(a) Thermometers

(ii) Iron

(b) Electric wire

(iii) Aluminium

(c) Wrapping food

(iv) Carbon

(d) Jewellery

(v) Copper

(e) Machinery

(vi) Mercury

(f) Fuel

Solution: i-d, ii-e, iii-c, iv-f, v-b, vi-a

Gold is highly lustrous. So, we use it to make jewellery.

Iron is a hard metal. We use it to make machinery.

Carbon is a black-coloured non-metal. We use it as fuel.

We use copper to make electrical wires. It is done so because copper is highly ductile and good conductor of electricity.

Mercury is a metal that is found in a liquid state. It rises and falls due to changes in temperature. So, it is used in thermometers to tell body temperature.


Question 9. What happens when

(a) Dilute sulphuric acid is poured on a copper plate?

(b) Iron nails are placed in copper sulphate solution? Write word equations of the reactions involved.

Solution:

(a) When we pour dilute sulphuric acid on a copper plate, no reaction occurs.

(b) Iron is more reactive than copper. When we keep iron nails in blue-coloured copper sulphate solution, iron displaces copper and forms green-coloured iron sulphate and copper.


class 8 science chapter 4 question 9

Question 10. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.

(a) How will she find the nature of the gas?

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

Solution:

(a) The charcoal on burning release carbon dioxide gas. When we put a few drops of water and cover the test tube and shake it well. Carbon dioxide reacts with water and forms carbonic acid. To this liquid, when we blue litmus paper, it will turn red. This proves that the gas is acidic in nature.

class 8 science chapter 4 question 10

Question 11. 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?

Solution: Goldsmith uses aqua-regia (mixture of hydrochloric acid and nitric acid) to clean gold ornaments. While doing so, the outer layer of gold dissolves, and the inner shiny metal comes out. Due to this, there is reduction in weight of Reeta’s jewellery.





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