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NCERT Revision notes for class 8 Science Materials: metals and non metals

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Metal:

Metal is a substance that is hard, shiny, ductile and allows heat and electricity to travel through it.

Properties of metal

  1. Malleability
  2. Ductility
  3. Sonorous
  4. Lustrous  
  5. Good conductor of heat and electricity

The property through which the metal can be drawn into thin sheets is called malleability.

The property through which the metal can be drawn into wires is called ductility.

Sonorous is the property that allows the metal to produce ringing sound.

Metals have shine surface. This property is called lustrous.

Heat and electricity can be easily passed through metals. Example: copper is used in wiring and aluminum is used in making utensils.

Non-metal

Non-metal is a substance that generally does not have shine and are found in many colors.

Properties of non-metals

  1. Non-metals are poor conductors of electricity.
  2. They are found in many colors.
  3. Non-metals cannot be drawn into wire and sheets.
  4. They do not produce ringing sound.
  5. They generally do not react with air and water.

Metalloids:

The substance that has some property of both metals and non-metals are called metalloids. Example: Silicon.

Chemical properties of metal and non-metals

Reaction with oxygen

Metals: metals generally react with oxygen to form oxide. Example: Magnesium (Mg) + oxygen (O2) -> Magnesium oxide (MgO)

Non-metals: non-metal generally does not react with oxygen.

Reaction with water

Metals: metals react with water to form metal hydroxide. Example: Sodium (Na) + water (H2O) -> sodium hydroxide (NaOH)

Non-metals: non-metals do not react with water.

Reaction with acid

Metals: metals react with acids to produce hydrogen gas.

Non-metals: non-metals do not react with acids.

Reaction with bases

Metals: metals react with sodium hydroxide to produce hydrogen gas.

What is displacement reaction?

 The reaction in which the highly reactive substance displaces the least reactive substance from its compound is called displacement reaction.

Example: Copper Sulphate (CuSO4) + Zinc (Zn) -> Zinc Sulphate (ZnSO4) + Copper (Cu)

Atom:

The smallest particle that cannot be further divided into smaller particle is called atom.

Uses of metals

Metals are used in manufacturing of Aeroplane, automobiles, trains, utensils and water boilers.

Uses of non-metals

  1. Water is non-metal, which is necessary for our survival.
  2. Plastic a non-metal is used in making storage containers, pencil box, etc.
  3. Cotton is a non-metal used in making our clothes.
  4. Medicines are non-metal which are used for treatment.

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