Extra 30 short questions and answers from Chapter:3 Metals and Non-Metals for Class 10 CBSE Science:

 

What are the physical properties of metals?

 

Ans:

Metals are generally malleable, ductile, good conductors of heat and electricity, have high melting and boiling points, and possess metallic

lustre.

 

Why are metals good conductors of electricity?

 

Ans:

Metals contain free electrons that can move easily through the metal lattice, allowing electricity to flow.

 

Define malleability and ductility with examples.

 

Ans:

Malleability:

The ability of a metal to be hammered into thin sheets (e.g., Gold, Aluminium).

Ductility:

The ability of a metal to be drawn into thin wires (e.g., Copper, Silver).

 

Why is sodium stored in kerosene?

 

Ans:

Sodium is highly reactive and reacts with oxygen and moisture in the air, producing heat and catching fire. Storing it in kerosene prevents such reactions.

 

Name two metals that do not react with water.

 

Ans:

Copper (Cu) and Gold (Au) do not react with water.

 

What happens when a metal reacts with an acid? Give an example.

 

Ans:

Metals react with acids to form salt and hydrogen gas.

 

Example:

 

Zn+2HCl→ZnCl2+H2Zn + 2HCl → ZnCl_2 + H_2Zn+2HCl→ZnCl2​+H2​

 

Why is gold preferred for making

jewellery

?

 

Ans:

Gold is highly malleable, ductile, has a bright

lustre

, and does not corrode, making it ideal for

jewellery

.

 

What is galvanization? Why is it done?

 

Ans:

Galvanization is the process of coating iron with zinc to prevent rusting. Zinc forms a protective layer that prevents iron from reacting with moisture and oxygen.

 

Which metal is used for making aircraft and why?

 

Ans:

Aluminium is used for making aircraft because it is lightweight, strong, corrosion-resistant, and has good tensile strength.

 

Why is graphite a good conductor of electricity while diamond is not?

 

Ans:

Graphite has free electrons that can move and conduct electricity, whereas diamond has all valence electrons bonded, making it an insulator.

 

Name the metal that exists in the liquid state at room temperature.

 

Ans:

Mercury (Hg) is the only metal that is liquid at room temperature.

 

What is meant by amphoteric oxides? Give an example.

 

Ans:

Amphoteric oxides are oxides that react with both acids and bases to form salt and water.

 

Example: Aluminium oxide (

Al₂O

₃

)

With acid:

Al₂O

₃ + 6HCl → 2AlCl₃ + 3H₂O

With base:

Al₂O

₃ + 2NaOH → 2NaAlO₂ + H₂O

 

What happens when copper sulphate solution is treated with iron nails?

 

Ans:

Iron displaces copper from copper sulphate solution, forming iron sulphate and depositing copper.

 

Fe +

CuSO

₄ →

FeSO

₄ + Cu

 

Why does aluminium not corrode easily?

 

Ans:

Aluminium forms a protective layer of aluminium oxide (

Al₂O

₃

) on its surface, preventing further corrosion.

 

What is an alloy? Give two examples.

 

Ans:

An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.

 

Examples:

Brass

(Copper + Zinc)

Bronze

(Copper + Tin)

 

Name two metals that do not react with hydrochloric acid.

 

Ans:

Copper (Cu) and Silver (Ag) do not react with hydrochloric acid.

 

What are the components of stainless steel?

 

Ans:

Stainless steel is an alloy of

Iron (Fe), Chromium (Cr), Nickel (Ni), and Carbon (C)

.

 

How is the corrosion of iron prevented?

 

Ans:

Corrosion of iron can be prevented by:

Painting

Galvanization (coating with zinc)

Oiling and greasing

Using stainless steel (alloying)

 

What is the chemical name and formula of rust?

 

Ans:

Rust is

hydrated

iron(

III) oxide

, with the formula

Fe₂O

₃·

xH₂O

.

 

Name two non-metals that are essential for life.

 

Ans:

Oxygen (

O₂

) – Required for respiration.

 

Carbon (

C

) – Essential in organic molecules like carbohydrates and proteins.

 

Why are metals sonorous?

 

Ans:

Metals produce a ringing sound when struck due to their elastic nature, making them sonorous.

 

What happens when magnesium reacts with hot water?

 

Ans:

Magnesium reacts slowly with hot water to form magnesium hydroxide and hydrogen gas.

 

Mg + 2H₂O →

Mg(

OH)₂ + H₂

 

Why is iron used in construction?

 

Ans:

Iron is strong, durable, cheap, and can be alloyed with carbon to form steel, which has high tensile strength.

 

Write the reaction of sodium with water.

 

Ans:

 

2Na + 2H₂O → 2NaOH + H₂

 

Sodium reacts violently with water, producing sodium hydroxide and hydrogen gas.

 

What is the difference between roasting and calcination?

 

Ans:

Roasting:

Heating sulphide ores in presence of oxygen. (

ZnS + O₂ →

ZnO

+ SO₂

)

Calcination:

Heating carbonate ores in absence of oxygen. (

CaCO

₃ →

CaO

+ CO₂

)

 

Why does silver turn black over time?

 

Ans:

Silver reacts with

hydrogen sulphide (H₂S)

in air to form

silver sulphide (

Ag₂S

)

, which is black.

 

Why does copper turn green over time?

 

Ans:

Copper reacts with

CO₂, water, and oxygen

to form

copper carbonate (

CuCO

₃) and copper hydroxide (

Cu(

OH)₂)

, which gives a green coating.

 

Write the chemical equation for the reaction of zinc with hydrochloric acid.

 

Ans:

 

Zn + 2HCl →

ZnCl

₂ + H₂

 

How does chlorine help in water purification?

 

Ans:

Chlorine is a strong oxidizing agent that kills bacteria and germs in water, making it safe for drinking.

 

Why is aluminium used in making soft drink cans?

 

Ans:

Aluminium is

lightweight, non-corrosive, and can be easily moulded

, making it suitable for beverage cans.