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4. Materials – Metals and Non Metals

This chapter talks about materials that are used to create various objects around us and the comparison between them

All the objects around us are made up of some material. Different materials have different properties. Depending upon the appearance, hardness, lustre and few other properties, materials can be divided into

  1. Metals
  2. Non Metals

There are some elements, which exhibit the properties of both Metals and Non Metals. They are called Metalloids

For Example

  1. Metals – Iron (Fe) and Copper (Cu), Gold (Au) and Silver (Ag)
  2. Non Metal – Carbon (C), Sulphur (S) and Lead (Pb)
  3. Metalloids – Boron (B), Silicon (Si) and Germanium (Ge)

4.1      Physical Properties of Materials

The following attributes of a material are called Physical Properties

  1. Strength and Hardness
  2. Lustre – Shine on their surface
  3. Malleability – The ability to be beaten into sheets
  4. Ductility – The ability to be drawn into wires
  5. Sonorousness (also sonority) – The ability to produce sound when struck
  6. Conductivity of Heat
  7. Conductivity of Electricity

Metals and Non-Metals have different physical properties

Physical Property Metals Non Metals
Strength and Hardness Generally, they are Strong and hard. However there are a few exceptions
  • Sodium (Na) & Potassium (k) are so soft, that they can be cut with a knife
  • Mercury is a metal which is liquid at room temperature
Soft
Lustre Shiny Non Shiny/ dull
Malleability Malleable Non Malleable – Cannot be beaten into sheet, as they are brittle and break into powder/small pieces
Ductility Ductile Non Ductile – Cannot be drawn into a wire, as they are brittle
Sonorousness Sonorous – Make sound when struck with another hard object Non Sonorous
Conductivity of Heat Good Conductors of Heat Bad Conductors of Heat
Conductivity of Electricity Good Conductors of Electricity Bad Conductors of Electricity

4.2      Chemical Properties of Materials

The following attributes of a material are called its Chemical Properties

  1. How does it react with Oxygen
  2. How does it react with Water
  3. How does it react with Acids
  4. How does it react with Bases
  5. Ability to displace other materials from its compounds
Chemical Property Metals Non Metals
Reaction with Oxygen Most metals oxidize in the presence of moisture and form a layer of oxide (salt) on their surface. This is called rusting

The generated salt is basic in nature

 

For example

Iron (Fe) + Oxygen (O2) + Water (H2O) -> ????

Most non metals oxidize in the presence of heat and oxides which are in gaseous form

The generated oxides are acidic

 

For example

Sulphur (S) + Oxygen (O2)  -> Sulphur dioxide (SO2)

Reaction with Water All metals react with Water (H2O), some like Sodium (Na) react vigorously, whereas others like Iron (Fe) react slowly

 

Sodium is kept in kerosene oil to cutoff its contact with water and air(moisture)

Generally, non-metals do not react with water

 

For example

Phosphorous is kept in water to cutoff its contact with air (oxygen)

Reaction with Acids Metals react with acids to produce Hydrogen (H) gas. The reaction produces a pop sound, which is due to the presence of Hydrogen Gas.

 

Generally, Non metals do not react with acids

 

 

Reaction with Bases Metals react with bases to produce Hydrogen (H) gas. Reactions of Non Metals with bases are complex
Ability to displace materials from its compounds In an aqueous solution, a more reactive metal will replace less reactive metal from its compound

For example

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

 

Generally, Non Metals are less reactive and do not replace materials from their compounds

4.3      Uses of Materials

Both Metals and Non Metals have their own uses

Metals are used in the making of

  1. Kitchen utensils
  2. Electrical wires
  3. Tools like hammers
  4. Ornaments

Metals are also present in human body as well as plants in the form of salts, which can be dissolved and get absorbed by the body

Non Metals are used in the making of

  1. Fertilizers
  2. Medicines
  3. Crackers
  4. Fabrics – For example, Nylon
  5. Food products like Vinegar