DAV Class 8 Science Solution Chapter 3 Metals and Non-Metals

DAV Class 8 Science Solution Chapter 3 Metals and Non-Metals

DAV School Books Class 8 Science Solution Chapter 3 Metals and Non-Metals all Question Answer. DAV Class 8 3rd Chapter Metals and Non-Metals full Chapter explanation by expert teacher.

DAV Class 8 Science Solution Chapter 3 Metals and Non-MetalsDAV School Books Class 8 Science Solution Chapter 3 Metals and Non-Metals

 

A.) Fill in the blanks.

1.) The property, due to which a metal piece can be hammered into thin sheets, is known as ___________.

2.) Bronze is an alloy of ___________ and ___________.

3.) Gold is mixed with ___________ and /or ___________ to make it hard.

4.) ___________ is the only non-metal to have a natural lustre.

5.) ___________ is a non-metal which catches fire in air.

6.) The only metal, which exists in the liquid state at room temperatures, is ___________.

Answer: (1) malleability (2) copper, tin (3) silver, copper (4) Iodine (5) Phosphorus (6) mercury

 

B.) Match the following

1.    Hardest substance a. bromine
2.    Aluminium ore b. graphite
3.    A non-metal, normally existing in liquid state c. bauxite
4.    A good electrical conductor d. diamond
5.    A metalloid e. arsenic

 Answer: (1) d, (2) c, (3) a, (4) b, (5) e

 

C.) Tick the correct option.

1.) The two most abundant metals, found in the earth’s crust, are-

Answer: aluminium and iron

2.) The metals, used in making the alloy ‘german silver’, are-

Answer: copper ,zinc  and nickel

3.) When a metal reacts with oxygen, the resulting oxide of the metal-

Answer: The resultant oxide will be basic in nature.

4.) Out of the metals, gold, silver, copper and aluminium, the one, that is most ductile, is-

Answer: gold

5.) Two of the metals, that cannot be stored either in air, or under water, are-

Answer: potassium and sodium

 

D.) Answer the following questions in brief.

1.) Name (i) one metal and (ii) one non-metal which normally exists in the liquid state.

Answer: (i) Mercury (ii) Bromine

 

2.) State the fraction of gold present in an 18-carat gold piece.

Answer: Pure gold is measured in the unit carats and  it is said pure solid gold is usually 24 carats. 18 carat means ,18 portion of gold and 6 parts of impurities. Hence,  gold present in 18 carats = 18/24 = ¾ th.

 

3.) State the property of copper wires that makes them useful for electrical fittings.

Answer: the property of copper wires that makes them useful for electrical fittings are:

  • Electric current flows well through copper.
  • It can be moulded and is ductile.
  • Additionally, copper is cheap.

 

4.) Define an alloy.

Answer: A homogenous mixture of two or more metals, or a metal and a non-metal is known as an alloy.

 

5.) List any two uses of non-metals.

Non metals are used for –

  • Non metals like nitrogen that is required by plants for protein synthesis is used in the manufacture of fertilisers
  • Diamond, which is known to be a precious gemstone is also a non metal and is used for ornamental purposes.

 

E.) Answer the following questions.

1.) Write the balanced chemical equations for the following reactions:

(a) sodium reacts with oxygen

Answer: 4Na (Sodium) + O2 (Oxygen) → 2Na2O (Sodium Oxide)

(b) aluminium reacts with dilute hydrochloric acid

Answer: 2Al (s) + 6HCl (aq) → 2AlCl3 (aq) + 3H2 (g)

 

2.) Why are gold and platinum suitable for making jewellery?

Answer: Golden Platinum are both used for making jewellery because not only are they malleable and ductile but also they are way below in the reactivity series hence are unreactive to most of the acids water and the substances .They also have and unique Shine which makes them fit for being moulded into jewellery

 

3.) ‘Sodium and potassium is stored under kerosene. Give reason.

Answer: Sodium and potassium both are high up in the reactivity series as a result they might react to air as well as temperature and humidity as a result it can catch fire and can cause danger however it is unreactive to kerosene and paraffin wax hence it is stored in these.

 

4.) Why is bronze preferred over copper metal for making statues?

Answer: Bronze is an alloy as a result it is much more strong in nature and is resistant to corrosion

Updated: January 28, 2023 — 11:32 am

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