Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Science Class 8

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Class 8 : Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

The document Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes is a part of the Class 8 Course Science Class 8.
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CHEMICAL PROPERTIES OF METALS AND NON-METALS

REACTION OF METALS WITH OXYGEN

Metals form their oxides when react with oxygen.
Metal + oxygen → Metal oxide
Metal oxides are basic in nature.
Example:

(i) Reaction of Iron metal with oxygen:

When iron reacts with moist air, it forms rust. Rust is iron oxide. Articles made of iron, such as grills, fencing, etc. are getting rusted because of reaction with moist air.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes
Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev NotesRust is reddish brown in colour and is iron oxide.

Iron oxide is basic in nature. It turns red litmus blue.

(ii) Reaction of Magnesium metal with oxygen:

When magnesium is burnt in air, it forms magnesium oxide. Burning in air means reaction with oxygen.
Magnesium (Mg) + Oxygen (O2) → MgO (Magnesium oxide)
Magnesium oxide forms magnesium hydroxide with water. Solution of Magnesium oxide turns red litmus paper blue. This means magnesium oxide is basic in nature.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

REACTION OF NON-METALS WITH OXYGEN

Non-metals forms their oxides when react with oxygen.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Thus, Non-metal forms their oxide when reacts with oxygen.

Non-metal oxides are acidic in nature.

(i) Reaction of sulphur with oxygen:

When sulphur is burnt in air, it forms sulphur dioxide.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Solution of sulphur dioxide turns blue litmus paper red. Sulphur dioxide forms sulphurous acid when dissolved in water. Thus, sulphur dioxide is basic in nature.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

(ii) Reaction of carbon with oxygen:

When carbon is burnt in air, it forms carbon dioxide. You can observe that when coal (carbon) is burnt it forms smoke, which contains carbon dioxide.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Carbon dioxide is acidic in nature. The solution of carbon dioxide in water turns blue litmus paper red.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

REACTION OF METALS AND NON-METALS WITH WATER

Generally, metals form respective hydroxides when they react with water. Some metals react vigorously with water like in case of sodium. It is stored in kerosene. While, some metals reacts very slowly with water like in case of iron.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes
(i) Reaction of sodium metal with water:

Sodium metal vigorously reacts with water and forms sodium hydroxide along with lot of heat.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev NotesReaction of Sodium with water(ii) Reaction of potassium with water:

Potassium metal vigorously reacts with water and forms potassium hydroxide along with lot of heat.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes


For Non-metals:
Non-metals generally do not react with water. Rather some non-metals which react with air vigorously are stored in water.

REACTION OF METALS AND NON-METALS WITH DILUTE ACID:

Metals give hydrogen gas when they react with dilute acid.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes
(i) Reaction of zinc with dilute acid:

Zinc gives hydrogen gas along with zinc chloride when it reacts with hydrochloric acid.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Similarly, zinc gives hydrogen gas along with zinc sulphate when it reacts with sulphuric acid.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

This method is used to produce hydrogen gas in laboratory.

(ii) Reaction of sodium metal with dilute acid:

Sodium gives hydrogen gas and sodium chloride when reacts with dilute hydrochloric acid (HCl).

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

(iii) Reaction of Aluminium with dilute acid:

Aluminium gives hydrogen gas along with aluminium chloride when it reacts with dilute hydrochloric acid.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Copper does not react with dilute sulphuric acid even on heating, but it reacts with concentrated sulphuric acid. Copper, silver and gold are considered as noble metals as do not react with dilute acid.
For Non-Metals:

Generally, non-metals do not react with dilute acid.

Reaction OF METALS AND NON-METALS WITH BASE

Metals give hydrogen gas when they react with a base.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

(i) Reaction of aluminium metal with sodium hydroxide:

Aluminium metal forms hydrogen gas and sodium aluminate when it reacts with sodium hydroxide.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Similarly, zinc gives sodium zincate and hydrogen gas when it reacts with sodium hydroxide.

DISPLACEMENT REACTION

During reaction if a metal replaces another metal from its compound then such reactions are called displacement reaction.
Metals can actually be arranged as per their reactivity order, thus, a more reactive metal will always displace a less reactive metal from its compound but a less reactive one cannot replace a more reactive metal.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

In the above equation, metal A is more reactive than metal B.
Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

Example:

(i) When aluminium metal is dipped in the solution of copper sulphate, it forms aluminium sulphate and copper.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

(ii) When iron reacts with solution of copper sulphate, it gives iron sulphate and copper.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes

In the above two reactions, aluminium and iron are more reactive than copper, that’s why they replace copper from the solution of copper sulphate.

When copper metal is dipped in the solution of aluminium nitrate, no reaction takes place. Because copper is less reactive than aluminium.

Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes


USE OF METALS AND NON-METALS

Use of metals:

  1. Metals being hard, tough are used in manufacturing automobiles, machinery, trains, satellites, aeroplanes, industrial gadgets.
    Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes
  2. Due to its characteristic of being a good conductor of electricity and ductility it is used in making wires, electrical appliances, circuits and many more.
    Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes
  3. Being a good conductor of heat it is used in making utensils, water boilers.
    Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes
  4. Gold is used in making ornaments.
  5. Silver is used in making ornaments.

Use of Non-metals:

  1. The number of non-metals is very less in comparison to metals and non-metals are more useful for us. So far only 22 non-metals are discovered.
  2. We breathe oxygen which is a non-metal. Without oxygen no one can live.
  3. Sodium chloride (common salt) cannot be formed without chlorine (a non-metal) which we use to enhance the taste of food. Without using common salt, food is tasteless.
  4. Nitrogen is used in making fertilizers.
  5. It is used as an antiseptic and applied on wounds.
  6. It is used as disinfectant.
    Notes of the Chapter - Materials:Metals & Non-Metals, Science, Class 8 | EduRev Notes
  7. It is used in crackers.
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