Chapter 3| Metals and Non-Metals| Class- 8 DAV Science Solutions

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Class- 8 DAV Science Metals and Non-Metals Question and Answer

A. Fill in the blanks.

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

2. Bronze is an alloy of copper and tin.

3. Gold is mixed with copper and/or silver to make it hard.

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

5. Phosphorous is a non-metal which catches fire in the air.

6. The only metal, which exists in the liquid state at room temperature, is mercury.


B. Match the following.

1. Hardest substance- Diamond

2. Aluminium ore- Bauxite

3. A non-metal, normally, existing in the liquid state- Bromine

4. A good electrical conductor- Graphite

5. A metalloid- Arsenic

C. Tick the correct options.

The two most abundant metals, found in the earth’s crust, are—

A. Aluminium and copper
B. aluminium and iron
C.iron and copper
D.iron and silver

Answer- aluminium and iron

The metals, used in making the alloy ‘german silver’, are-
A.copper + zinc + tin
B. copper + nickel + tin
C.copper + zinc + nickel D.copper + nickel + cobalt

Answer – Copper+zinc+nickel

When a metal reacts with oxygen, the resulting oxide of the metal—
is a neutral oxide
is a acidic oxide
turns blue litmus red
Answer: is a basic oxide

Out of the metals, gold, silver, copper and aluminium, the one, that is most ductile, is—
gold
aluminium
silver
copper

Answer:Gold

Two of the metals, that cannot be stored either in air, or under water, are—
sodium and magnesium
magnesium and calcium
calcium and potassium
potassium and sodium

Answer:potassium and sodium

D. Answer the following questions in brief.

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

Mercury is a metal that exists as a liquid at room temperature.

Bromine is a non-metal that exists as a liquid at room temperature.

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

Pure gold is 24 carat, so 18 carat would be 18/24, or 3/4. 75% is correct.

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

Copper wires are used to make electrical fittings because copper is a good conductor of electricity and also ductile.

Define an alloy.

Alloy is a homogenous mixture of one or more metals, or metal or nonmetal.

List any two uses of non-metals.

Potassium is used in fertilizer. Graphite is used in making leads.

E. Answer the following questions.

Write the balanced chemical equations for the following reactions: (a) sodium reacts with oxygen (b) aluminium reacts with dilute hydrochloric acid

a.) 4 Na + O2 → 2 Na2O

b.) Aluminum reacts with hydrochloric acid to produce aluminum chloride and hydrogen gas. Aluminum reacts with hydrochloric acid to produce aluminum chloride and hydrogen gas. The reaction is,2Al(s)+6HCl(aq)→2AlCl3​(aq)+3H2​(g) 

Why are gold and platinum suitable for making jewellery?

The following are the reasons why platinum gold and silver are used to produce jewellery. They are highly lustrous metals and is highly resistant to corrosion.
They may be molded into any shape or design because they are highly malleable and ductile.

‘Sodium and potassium is stored under kerosene.’ Give reason.

Sodium is very reactive that it reacts vigorously in air and catches fire. Hence to protect it, it is stored under kerosene.

Why is bronze preferred over copper metal for making statues?

Bronze is used to construct statues because it is tougher and more pliable than other metals. It’s also ductile, which means it can be readily sculpted into a statue. As a result, bronze is more commonly used for statues than copper.

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