Chapter 4 – Materials: Metals And Non-Metals Revision Notes

Metals and Non-Metals Class 8 Notes

These Metals and Non-Metals Class 8 Notes will surely help you to get good marks in your school exams.

Chapter Content

Physical Properties

What do you understand by physical properties of substances?

Any property of matter that can be observed or measured without changing the identity of the matter.

Physical properties do not change the chemical nature of the matter.

It is observed with touch, taste, smell and sight.

It is measured with balances, graduated cylinders, etc.

Chemical Properties

What do you understand by Chemical Properties?

It is the characteristic or ability of a substance to react to form new substances.

Also Read: Chapter 12 Friction Class 8 Notes Pdf

Chemical property can also be defined as how a substance interacts with other substances.

Physical Properties of Metals and Non-Metals

Important Facts Metals and Non-Metals

• Generally, all the metals are ductile, malleable, sonorous, hard and high strength and also mostly exist in solid form, but there are a few exceptions.
• Mercury is a liquid metal.
• Diamond is a non-metal but is the hardest element.
•  Most Ductile element – Gold
• Most Malleable Element – Gold

Chemical Properties of Metals And Non-Metals

Reaction of Metals with Oxygen

When metals are burnt in the air, they form metal oxides.

Metal + Oxygen → Metal Oxide

• Metal oxide formed is usually basic in nature.
• The metal oxides can be Amphoteric in nature.

Amphoteric Oxide

Question: What is an Amphoteric Oxide?

Answer: The metal oxides that show acidic as well as basic behaviors.

Examples: The oxides of aluminium (Al2O3), Zinc (ZnO), Tin, etc. are amphoteric in nature.

Important Points to Remember

• Most metal oxides are insoluble in water, but some may dissolve to form alkalis.
• Sodium (Na) and Potassium (K) react vigorously with air.
• Silver (Ag) and Gold (Au) do not react with air even on heating (high temperature).
• Cu, Mg, Al, Zn, Pb react with air (oxygen) to form a protective layer of oxide.
• Iron doesn’t burn on heating but the iron filings burn vigorously after being heated.

Corrosion

What do you understand by corrosion?

It is a natural process where a metal when exposed to moist air gets damaged.

Reaction of Non-Metals with Oxygen

Except white Phosphorus non-metals do not react with air (oxygen) at room temperature to form nonmetal oxides.

• This is the reason that White Phosphorus is stored  under Water.
• Phosphorous Varieties: White, Black and Red.

Non-Metals + Oxygen → Non-metal oxides

When ignited carbon and Sulphur burn to form respective oxides.

C (s) + O2 (g) → CO2 (s)

2C + O2 → 2CO (Insufficient supply of air form carbon monoxide)

S (s) + O2 (g) → SO2 (g)

Generally, all non-metals oxides are acidic in nature.

CO2 + H2O → H2CO3 (Carbonic Acid)

SO2 + H2O → H2SO3 (Sulphurous Acid)

• CO, H2O, NO, N2O are neutral non-metal oxides.

Reaction of Metals with Water

Metal + Water → Metal oxide + H2 (g)

(metal oxide dissolves in water to form metal hydroxide)

Metal Oxide + Water → Metal Hydroxide + Hydrogen

• Sodium (Na) and Potassium (K) are so reactive that they react even with cold water.

Question: Why sodium and potassium catches fire when put in water?

Answer: When Sodium and Potassium is put in water it releases hydrogen gas and also a lot of heat is released during the reaction. Due to this heat hydrogen gas catches fire.

• Calcium (Ca) also react with cold water but not so violently like Na and K.
• Calcium when put in water starts floating due to the release of hydrogen gas during the reaction and sticking of this gas on the calcium.
• Magnesium (Mg) do not react with cold water but reacts with water water and starts floating like Calcium.
• Al, Zn, Fe reacts with his team to form metal oxide and hydrogen.

2Al + 3H2O(steam) → Al2O3 + 3H2

• Gold (Au), Silver (Ag), Copper (Cu), Lead (Pb) do not react with water at all.

Reaction of Non-Metals with Water

Generally, the non-metals do not react with water.

• Chlorine dissolves in water to form an acidic solution and when this solution is heated or kept in sunlight oxygen is liberated and HCL is formed.

2Cl2 + 2H2O → 4HCl + O2

Water Gas

What do you understand by Water Gas?

Water Gas is a gaseous mixture of carbon monoxide and Hydrogen. It is formed when steam is passed over red-hot coke (carbon).

C + H2O (steam) → CO + H2

Reaction of Metals with Acids

Metal + Acid → Metal Salt + Hydrogen (g)

• Metals above hydrogen in the reactivity series or more reactive than hydrogen will displace hydrogen from its dilute acid.
• Metals below hydrogen will not be able to displace and so no reaction will take place.

Reaction of Non-Metals with Acids

Non-Metals do not react with a acid in ordinary conditions.

But, Charcoal on the action with sulphuric acid forms carbon dioxide, sulphur dioxide and water.

Charcoal (C) + H2SO4 → CO2 + 2SO2 + 2H2O

Reaction of Metals with Bases

Only some metals react with a base to give salt and hydrogen gas.

Example: Copper (Cu), Zinc (Zn), Lead (Pb), Aluminium (Al), Tin (Sn), Beryllium (Be).

Question: Why metals do not react with a base?

Most Metals do not react with a base because metals have basic properties.

Only those metals react with a base that an effort Eric in nature like Copper Zinc, Aluminium, Tin etc.

Zn + 2NaOH → Na2ZnO2 (Sodium Zincate) + H2

Reaction of Non-Metals with Bases

The reaction of nonmetals with the base are complex.

Reactivity Series

Displacement Reaction

Displacement reaction is a reaction in which a more reactive metal or non-metal displaces a less reactive metal or non-metal from their salt solutions.

• Since magnesium is more reactive than copper so magnesium displaces copper from its solution copper sulphate.

Mg + CuSO4 → MgSO4 + Cu

• Chlorine displaces Bromine from Bromides

2KBr (Potassium Bromide) + Cl2 → 2KCl + Br2

Uses of Metals

Here is the list of few uses of metals.

• Iron is used for construction works, making steel, engines, gates etc
• Silver and gold is used for jewellery purpose
• Mercury is used in Thermometers
• Copper is used in making electrical wires cables, alloys, utensils, coins, etc.

Uses of Non-Metals

Here is the list of few uses of non-metals.

• Iodine is used for medical purpose (tincture of Iodine)
• Sulphur is used for manufacturing gun powder, used in vulcanisation of rubber.
• Phosphorus is used for manufacturing fertilisers
• Oxygen is used for respiration by living organisms.
• Coal (Carbon) is used as a fuel.

We hope you like this notes on metals and non-metals.