Lesson: Metals and Non-metals
Topic 1

Question: 1

Give examples of two metals.

Solution:

Iron and copper

Question: 2

Give examples of two non-metals.

Solution:

Carbon and nitrogen

Question: 3

Why are immersion rods for heating liquids made of metallic substances?

Solution:

Immersion rods are made of metallic substances because metals are good conductors of heat and electricity. They get hot very quickly when electric current is passed through them and are good for heating liquids.

Question: 4

A. You must have seen in the laboratory that sodium is always stored in kerosene oil. Why?

B. Name a non-metal that is very reactive and is stored in water.

Solution:

A. Sodium is very active element. It reacts vigorously with oxygen present in air by combining with it at room temperature and burning. It reacts violently with water also and produces hydrogen gas, which can get ignited by the heat of the reaction. To prevent sodium from reacting with oxygen or water vapour in the air, it is stored in kerosene.

B. Phosphorous is a non-metal that ignites when it comes into contact with air. So, it is stored in water.

Question: 5

What are sonorous materials?

Solution:

Materials that emit a rich, ringing sound when hit, are called sonorous materials. Except for soft metals like sodium, all others are sonorous, while non-metals are not sonorous.

Question: 6

Define: (1) Malleability (2) Ductility (3) Metals (4) Non-metals

Solution:

Malleability: The property of a substance that allows it to be beaten into thin sheets, without breaking, is called malleability. This is one of the physical properties of metals.

Ductility: The property of a substance that allows it to be drawn into wires is called ductility. This is one of the physical properties of metals.

Metals: Metals are substances that exhibit the following physical properties:

· Hardness (except Sodium and Potassium)

· Lustre

· Mostly exist in a solid state (except Mercury)

· Malleability

· Ductility

· Sonority

· Conductivity of heat and electricity

Non-Metals: Non-metals are substances that are found in all the three states (solid, liquid and gaseous). They exhibit the following properties:

· Non-lustre

· Non-sonority

· Brittleness

· Poor conductivity of heat and electricity

Question: 7

Name a non-metal that exhibits the property of being a good electrical conductor.

Solution:

Carbon, in the form of graphite, exhibits good electrical conductivity.

Question: 8

Name a non-metal used for making fertilisers.

Solution:

Nitrogen is a non-metal that is used for making fertilisers.

Question: 9

Name a non-metal that is very hard.

Solution:

Carbon, in the form of a diamond, is a non-metal that is the hardest naturally occurring substance.

Question: 10

List different uses of metals that you come across in everyday life.

Solution:

Uses of metals are as follows:

· Iron along with other hard and malleable metals, is used in automobile and aviation industry.

· Aluminium is often used for making household items like utensils and foils.

· Metals such as copper, iron and aluminium are also used for making cooking utensils and water boilers.

· Copper and aluminium are used in electric wires because they are good conductors of electricity.

· Gold and silver are used for making jewellery because they are malleable and ductile.

Question: 11

What property of aluminium makes it useful for wrapping of food items?

Solution:

Aluminium has the property of malleability because of which it can be flattened into thin sheets. These sheets can be folded, bent and twisted in to different shapes to wrap food items. Moreover, aluminium is impervious to moisture and microbes.

Question: 12

Give reasons why:

i. Iron is used for construction of houses and bridges.

ii. Copper is used for making electrical wires.

Solution:

(i) Iron is used in construction of bridges and houses because iron, being a hard metal, has great strength. When cast with cement it forms reinforced concrete.

(ii) Copper is used for making electrical wires because it is ductile and is a good conductor of electricity.

Question: 13

What property of copper makes it useful as electric wires?

Solution:

The ability to conduct electricity effectively, as well as, the property of ductility makes copper useful in electric wires.

Question: 14

Which property of gold makes it suitable for making jewellery?

Solution:

Gold is suitable for making jewellery because it is:

• Lustrous

• Highly malleable

• Ductile

Topic 2

Question: 1

Define rust?

Solution:

Iron reacts with oxygen in the air to form iron oxide, which is reddish brown in colour. This is called rust.

Question: 2

What happens when iron nails are dropped in water in a test tube and left for a week?

Solution:

When iron nails are dipped in water for a week, a reddish-brown layer of iron oxide forms on them. This is known as rust.

Question: 3

What happens when a magnesium ribbon is burnt in air?

Solution:

When a magnesium ribbon is burnt in air it reacts with the oxygen in air to form magnesium oxide.

2Mg + O₂ → 2MgO

Question: 4

In a chemistry laboratory, Ritu drops some magnesium strips in blue coloured copper sulphate solution by mistake. What change will she observe in the colour of the solution?

Solution:

Magnesium is more reactive than copper. Therefore, it displaces copper from copper sulphate solution forming magnesium sulphate, due to which the blue colour of the copper sulphate solution turns colourless and a red colour deposition takes place on the magnesium trips due to the formation of copper powder on them.

Mg + CuSO₄ → MgSO₄ + Cu

Question: 5

What would happen if sulphuric acid was poured on a zinc plate?

Solution:

When metals react with acid their corresponding salt is formed and hydrogen gas is released. Therefore, zinc reacts with sulphuric acid to form zinc sulphate and hydrogen gas. The chemical reaction that takes place during the process is explained in the following chemical equation:

Zn + H₂SO₄ → ZnSO₄ + H₂

Question: 6

What happens if ash of magnesium is dissolved in water? Is the solution acidic or basic?

Solution:

When ash of magnesium, that is magnesium oxide, is dissolved in water, magnesium hydroxide is formed.

MgO + H₂O → Mg(OH)₂

The solution is basic. All metallic oxides are basic in nature, as their aqueous solutions turn red litmus blue.

Question: 7

Name the gas that is produced when dilute hydrochloric acid is added to any reactive metal.

Solution:

Hydrogen gas is produced when dilute HCl is added to a reactive metal. For example:

Fe(s) + H₂SO₄(dil.) → FeSO₄(aq) + H₂(g)

Question: 8

What do you observe when zinc is added to a solution of iron sulphate?

Solution:

The solution of iron sulphate slowly turns colourless and a grey coloured layer of Fe is deposited on the surface of the zinc.

Zn(s) + FeSO₄(aq) → ZnSO₄(aq) + Fe(s)

Question: 9

Why are lemon pickles not stored in an aluminium utensil?

Solution:

Lemon pickle is acidic in nature and should not be stored in aluminium utensils because aluminium being a metal readily reacts with acids to produce aluminium sulphate, which is toxic and therefore, poisons the lemon pickle.

Question: 10

List out some uses of non-metals.

Solution:

Some of the uses of non-metals are as follows $-$

i. Oxygen is used for respiration by plants and animals. It also supports the process of combustion.

ii. Compounds of nitrogen act as nutrients for the soil and plants. Fertilizers made of similar non-metallic compounds are extensively used in agriculture.

iii. Chlorine is popularly used as a disinfectant.

iv. Plastic and bakelite are used in kitchen and electrical appliances as they are heat and electrical insulators.

Question: 11

Which non-metal catches fire if exposed to air?

Solution:

Phosphorus