THE WORLD OF METALS AND NON-METALS – Class 7 - Science
SUMMARY
1. Introduction
Our earth is made of many substances.
Metals and non-metals are two important groups of elements.
They differ in appearance, properties, and uses.
2. Metals – General Properties
Shiny (lustrous)
Hard and strong
Good conductors of heat and electricity
Malleable (can be beaten into thin sheets)
Ductile (can be drawn into wires)
Usually solid at room temperature (except Mercury)
Examples: Iron, Copper, Aluminium, Gold, Silver
3. Non-Metals – General Properties
Dull in appearance (not shiny)
Brittle (breaks easily)
Poor conductors of heat and electricity (insulators)
Not malleable, not ductile
Can be solid, liquid or gas
Examples: Carbon, Sulphur, Phosphorus, Oxygen, Nitrogen
4. Metalloids
Some elements show properties of both metals and non-metals.
Example: Silicon, Arsenic
5. Uses of Metals
Iron – construction of bridges, buildings, machinery
Aluminium – aircraft, utensils, foils
Copper – wires, utensils, coins
Gold & Silver – jewellery, coins
Mercury – thermometers
6. Uses of Non-Metals
Oxygen – breathing, combustion
Nitrogen – making fertilizers
Carbon – fuel (coal), pencils (graphite)
Sulphur – making gunpowder, medicines
Phosphorus – safety matches, fertilizers
7. Importance in Daily Life
Metals and non-metals are essential for industries, medicines, agriculture, transport, communication, and household needs.
In short:
Metals are shiny, strong, malleable, ductile, and good conductors.
Non-metals are usually dull, brittle, poor conductors.
Both play a major role in our daily life and industries.
SHORT QUESTIONS & ANSWERS
What are metals?
→ Elements that are generally hard, shiny, malleable, ductile, and good conductors of heat and electricity.
Give two examples of metals.
→ Iron, Aluminium.
What are non-metals?
→ Elements that are usually dull, brittle, poor conductors of heat and electricity.
Give two examples of non-metals.
→ Sulphur, Oxygen.
Name one metal that is liquid at room temperature.
→ Mercury.
Name one non-metal that is liquid at room temperature.
→ Bromine.
What is malleability?
→ The property of a metal to be beaten into thin sheets.
What is ductility?
→ The property of a metal to be drawn into thin wires.
Why is copper used in making electrical wires?
→ Because copper is a good conductor of electricity and ductile.
Why is aluminium used in making aircraft?
→ Because it is light in weight, strong, and does not corrode easily.
Name two metals used in jewellery.
→ Gold and Silver.
Name two metals used in making utensils.
→ Aluminium and Steel (Iron).
Which metal is used in thermometers? Why?
→ Mercury – because it is liquid and expands uniformly on heating.
Why is iron not used directly in bridges and buildings?
→ Because it rusts easily. Instead, steel (an alloy of iron) is used.
What is an alloy? Give one example.
→ A mixture of metals with other metals/non-metals. Example: Brass (Copper + Zinc).
Why is gold considered a precious metal?
→ Because it is rare, does not rust or corrode, and has high economic value.
Name one non-metal used in fertilizers.
→ Nitrogen (in the form of urea or ammonium compounds).
Which non-metal is used in pencils?
→ Carbon (Graphite form).
Which non-metal is essential for respiration?
→ Oxygen.
Name one non-metal used in safety matches.
→ Phosphorus.
Which non-metal is used in medicines and explosives?
→ Sulphur.
Why is aluminium foil used for wrapping food?
→ Because it is malleable, non-toxic, and resists corrosion.
What are metalloids? Give two examples.
→ Elements showing properties of both metals and non-metals. Examples: Silicon, Arsenic.
Why is silicon important?
→ Because it is used in making electronic devices like computers and mobiles.
Why are metals good conductors of electricity?
→ Because they have free electrons that carry current.
Why are non-metals poor conductors of electricity?
→ Because they do not have free electrons.
Which metal is used in making coins?
→ Copper, Nickel.
Why are cooking utensils made of metals?
→ Because metals are good conductors of heat.
Why is stainless steel preferred over iron?
→ Because stainless steel does not rust easily.
Name two non-metals that exist as gases.
→ Oxygen and Nitrogen.
Name one non-metal used in water purification.
→ Chlorine.
Which non-metal is found in diamonds?
→ Carbon.
Why is gold used in making ornaments?
→ Because it is lustrous, malleable, and does not tarnish.
Name a metal which is very soft and can be cut with a knife.
→ Sodium or Potassium.
Why are metals like sodium and potassium stored in kerosene?
→ Because they react quickly with air and water.
Which metal is known as ‘Queen of Metals’?
→ Aluminium.
Why is copper used in making hot water tanks?
→ Because it is a good conductor of heat and does not rust easily.
Why is oxygen called a supporter of combustion?
→ Because it helps in burning of fuels.
Name one non-metal used in making antiseptics.
→ Iodine.
Why is coal considered a non-metal?
→ Because it is a form of carbon, which is brittle and a poor conductor.
LONG QUESTION-ANSWERS
State the physical properties of metals.
→ Metals are generally lustrous (shiny), hard and strong. They are malleable (can be beaten into sheets), ductile (can be drawn into wires) and good conductors of heat and electricity. They usually have high melting and boiling points. Examples: Iron, Copper, Aluminium.
State the physical properties of non-metals.
→ Non-metals are usually dull in appearance, soft and brittle. They are not malleable or ductile. They are poor conductors of heat and electricity. They may be solids, liquids, or gases at room temperature. Examples: Sulphur, Oxygen, Carbon.
What are metalloids? Give examples.
→ Elements that show properties of both metals and non-metals are called metalloids. For example:
Silicon – shiny like a metal but brittle like a non-metal.
Arsenic – conducts electricity like a metal but is brittle like a non-metal.
What are alloys? Write examples and their uses.
→ An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.
Examples:
Brass (Copper + Zinc) – used in musical instruments.
Bronze (Copper + Tin) – used in statues and medals.
Stainless steel (Iron + Nickel + Chromium) – used in utensils, machinery.
Explain with examples why metals are used in making cooking utensils.
→ Metals are good conductors of heat and strong. Therefore, they allow heat to pass quickly and cook food evenly. Examples: Aluminium, Copper, Stainless steel.
Why are electrical wires made of copper and aluminium?
→ Because both are good conductors of electricity and ductile, hence can be drawn into thin wires without breaking.
What is malleability? Explain with examples.
→ Malleability is the property of metals to be beaten into thin sheets. Gold and Aluminium are highly malleable. That is why aluminium foil is used for wrapping food.
What is ductility? Explain with examples.
→ Ductility is the property of metals to be drawn into wires. Gold, Silver and Copper are highly ductile. One gram of gold can be drawn into thin wire several metres long.
Why is sodium not used in making utensils?
→ Sodium is a metal but it is very soft and reacts violently with water and air. Therefore, it is unsafe and unsuitable for making utensils.
Why are gold and silver used for making jewellery?
→ Because they are lustrous (shiny), highly malleable and ductile, do not corrode or tarnish easily, and have high economic value.
Describe the uses of metals in our daily life.
→ Metals are used in:
Construction (iron, steel, aluminium)
Electrical appliances (copper, aluminium)
Utensils (aluminium, stainless steel)
Jewellery (gold, silver, platinum)
Machinery and transport (iron, steel)
Describe the uses of non-metals in our daily life.
→ Non-metals are used in:
Breathing (oxygen)
Fertilizers (nitrogen, phosphorus)
Medicines and antiseptics (iodine, sulphur)
Fuel (coal, a form of carbon)
Matches and fireworks (phosphorus, sulphur)
Explain why diamond and graphite, though forms of carbon, are so different.
→ Diamond: Hardest natural substance, used in cutting tools, jewellery.
Graphite: Soft, slippery, good conductor of electricity, used in pencils, lubricants.
Difference is due to different arrangement of carbon atoms.
Why is mercury used in thermometers?
→ Because it is liquid at room temperature, expands uniformly on heating, and is shiny, making it easy to read.
Why is aluminium preferred over iron for making utensils and machinery?
→ Aluminium is light, strong, resistant to corrosion and a good conductor of heat. Unlike iron, it does not rust.
Write a note on rusting of iron and its prevention.
→ Rusting is the slow reaction of iron with oxygen and moisture forming reddish-brown iron oxide.
Prevention: Painting, galvanisation, oiling, greasing, and using stainless steel.
Explain the role of oxygen, nitrogen and carbon as non-metals in daily life.
→ Oxygen: essential for respiration, combustion.
Nitrogen: used in fertilizers, preserves food.
Carbon: used as fuel (coal), in pencils (graphite), diamonds for cutting tools and jewellery.
Why are coins not made of pure copper today?
→ Because copper is expensive and soft, gets worn out easily. Instead, cheaper alloys (nickel + copper, stainless steel) are used.
Why are gold and platinum considered noble metals?
→ Because they do not corrode or react with air, water, or most chemicals.
Explain why phosphorus is stored under water.
→ Because it is highly reactive with air and catches fire easily. Keeping it under water prevents contact with oxygen.
A student was asked to select a material for making a frying pan. Should he choose plastic or metal? Why?
→ Metal, because it is a good conductor of heat, strong, and can withstand high temperatures. Plastic melts easily and is a poor conductor.
Why is stainless steel preferred for making surgical instruments?
→ Because it is strong, corrosion-resistant, easy to sterilise, and does not rust.
Gold is more malleable than aluminium. Explain with a use.
→ Gold can be beaten into very thin foils (used in jewellery, temple decoration) whereas aluminium foils are used for wrapping food.
Why do electrical wires have plastic covering though the wire inside is metal?
→ The metal (copper/aluminium) conducts electricity, but the plastic covering insulates and prevents electric shock.
Explain why non-metals like oxygen and nitrogen are essential for life.
→ Oxygen is needed for respiration, nitrogen maintains balance of atmosphere and helps in plant growth through fertilizers.
Write a short note on chlorine and iodine as useful non-metals.
→ Chlorine: disinfectant, used in water purification, PVC plastics.
Iodine: antiseptic, used in medicines.
Why can aluminium not replace copper in all electrical appliances?
→ Though aluminium is a good conductor, it is less ductile and less durable than copper. Hence copper is preferred in delicate wiring.
Why is diamond valuable even though it is a non-metal?
→ Because it is the hardest natural material, has brilliant shine, and is rare. Used in jewellery and industrial cutting tools.
Why does sulphur not conduct electricity whereas graphite does?
→ Sulphur has no free electrons, but graphite has free electrons in its layered structure which conduct electricity.
Explain why silver and copper articles lose shine after some time.
→ Because they react with gases in air (like hydrogen sulphide, carbon dioxide) forming tarnished layers (silver sulphide, copper oxide).
List four differences between metals and non-metals.
(Mention lustre, conductivity, malleability, ductility).
Give reasons why coal is considered a non-metal.
→ Coal is brittle, dull, and a poor conductor (form of carbon).
Explain why alloys are better than pure metals.
→ Stronger, resistant to rust, harder, and often cheaper.
Why is helium (a non-metal gas) used in balloons instead of hydrogen?
→ Because helium is non-flammable, whereas hydrogen is highly explosive.
Write a note on importance of metals and non-metals in agriculture.
→ Metals like iron are used in tools, machinery, pipes.
Non-metals like nitrogen, phosphorus, potassium are used in fertilizers.
MCQS
Which of the following is a metal?
a) Sulphur
b) Carbon
c) Copper
d) Oxygen
→ c) Copper
Which of the following is a non-metal?
a) Iron
b) Sulphur
c) Aluminium
d) Zinc
→ b) Sulphur
The only liquid metal at room temperature is:
a) Sodium
b) Mercury
c) Aluminium
d) Iron
→ b) Mercury
Which non-metal is essential for respiration?
a) Carbon
b) Oxygen
c) Nitrogen
d) Sulphur
→ b) Oxygen
Which metal is used in making foils for wrapping food?
a) Iron
b) Aluminium
c) Copper
d) Zinc
→ b) Aluminium
Which non-metal is used in fertilizers?
a) Nitrogen
b) Sulphur
c) Iodine
d) Carbon
→ a) Nitrogen
The hardest natural substance is:
a) Iron
b) Graphite
c) Diamond
d) Quartz
→ c) Diamond
Which property allows metals to be beaten into sheets?
a) Ductility
b) Malleability
c) Hardness
d) Conductivity
→ b) Malleability
Which property allows metals to be drawn into wires?
a) Malleability
b) Brittleness
c) Ductility
d) Softness
→ c) Ductility
Which metal is used in thermometers?
a) Mercury
b) Sodium
c) Aluminium
d) Iron
→ a) Mercury
Which non-metal is used in pencils?
a) Graphite
b) Diamond
c) Phosphorus
d) Sulphur
→ a) Graphite
Which of the following is a good conductor of electricity?
a) Plastic
b) Rubber
c) Copper
d) Sulphur
→ c) Copper
Which non-metal is used in making antiseptics?
a) Nitrogen
b) Iodine
c) Oxygen
d) Phosphorus
→ b) Iodine
Which of these is NOT an alloy?
a) Brass
b) Bronze
c) Steel
d) Oxygen
→ d) Oxygen
The main metals in stainless steel are:
a) Copper, Zinc
b) Iron, Chromium, Nickel
c) Copper, Tin
d) Aluminium, Zinc
→ b) Iron, Chromium, Nickel
Which metal is used in jewellery along with gold?
a) Iron
b) Platinum
c) Zinc
d) Aluminium
→ b) Platinum
Which gas is given off when metals react with water?
a) Oxygen
b) Carbon dioxide
c) Hydrogen
d) Nitrogen
→ c) Hydrogen
Which non-metal is stored under water?
a) Sulphur
b) Phosphorus
c) Oxygen
d) Nitrogen
→ b) Phosphorus
Which is the most ductile metal?
a) Aluminium
b) Gold
c) Copper
d) Zinc
→ b) Gold
Which metal is used for making aircrafts because it is light?
a) Iron
b) Aluminium
c) Zinc
d) Copper
→ b) Aluminium
Which metal is found in liquid form?
a) Mercury
b) Sodium
c) Gold
d) Iron
→ a) Mercury
The gas used in filling balloons is:
a) Oxygen
b) Hydrogen
c) Helium
d) Nitrogen
→ c) Helium
Why is sodium not used for utensils?
a) Too heavy
b) Too hard
c) Too soft and reacts violently with water
d) Expensive
→ c) Too soft and reacts violently with water
Which non-metal is used in making safety matches?
a) Sulphur
b) Phosphorus
c) Iodine
d) Carbon
→ b) Phosphorus
Which is a property of non-metals?
a) Lustrous
b) Malleable
c) Brittle
d) Ductile
→ c) Brittle
Which non-metal is used to disinfect water?
a) Sulphur
b) Nitrogen
c) Chlorine
d) Oxygen
→ c) Chlorine
Which metal is used in making wires for electrical purposes?
a) Iron
b) Copper
c) Aluminium
d) Both (b) and (c)
→ d) Both (b) and (c)
Which of the following is NOT a property of metals?
a) Conductivity
b) Brittleness
c) Malleability
d) Ductility
→ b) Brittleness
Which form of carbon is used as fuel?
a) Diamond
b) Graphite
c) Coal
d) Charcoal
→ c) Coal
Which non-metal is used in making gunpowder?
a) Carbon
b) Nitrogen
c) Sulphur
d) Iodine
→ c) Sulphur
Which of these metals does not corrode easily?
a) Iron
b) Aluminium
c) Gold
d) Copper
→ c) Gold
Which is a noble metal?
a) Aluminium
b) Iron
c) Gold
d) Zinc
→ c) Gold
Which non-metal is used in making fertilizers along with nitrogen?
a) Sulphur
b) Phosphorus
c) Iodine
d) Helium
→ b) Phosphorus
What happens when iron is exposed to moist air for long?
a) Rusting
b) Tarnishing
c) Melting
d) Polishing
→ a) Rusting
Which of these is a metalloid?
a) Silicon
b) Oxygen
c) Zinc
d) Iron
→ a) Silicon
Which metal is mixed with copper to make bronze?
a) Zinc
b) Tin
c) Nickel
d) Aluminium
→ b) Tin
Which metal reacts vigorously with water producing hydrogen gas?
a) Gold
b) Sodium
c) Aluminium
d) Copper
→ b) Sodium
Why is graphite used in making electrodes?
a) Shiny
b) Soft
c) Conducts electricity
d) Cheap
→ c) Conducts electricity
Which of these is NOT a use of aluminium?
a) Aircrafts
b) Utensils
c) Jewellery
d) Foils
→ c) Jewellery
Which gas is essential for burning?
a) Nitrogen
b) Oxygen
c) Carbon dioxide
d) Hydrogen
→ b) Oxygen
