CBSE Notes for Class 8 Science Chapter 4 – Materials Metals and Non Metals

Important Notes for CBSE Class 8 Science Chapter 4 – Materials Metals and Non Metals. Materials Metals and Non Metals Class 8 Notes and Study Material Download in PDF form.

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Materials Metals and Non Metals Class 8 Notes

An important classification of elements is in terms of metals and non-metals. Most of the elements are metals. The remaining are either non-metals or metalloids. Metalloids possess character of both metals and non-metals.

  • Materials are mainly of two types:

1) Metals

i) Definition:These are substances characterized by high electrical and thermal conductivity. They also posses’ properties like malleability, ductility and light reflectivity.

ii) Examples:Aluminum, copper, iron, tin, gold. Around 90 naturally found elements are metals.

iii) Physical Properties:

    • Good conductors of heat and electricity
    • Ductility: The property of metals by which they can be drawn into wires.
    • Malleability: The property by which metals can be beaten into thin sheets is called malleability.
    • Metals are sonorous. It means they produce a ringing sound when they are struck with a hard object or beaten.
    • Metals are usually hard and they are lustrous or have a shiny appearance. An exception to this is Metals like sodium and potassium are soft.
    • Metals are normally found in solid state except Mercury is the only metal which is found in liquid state at room temperature.

iv) Chemical properties:

    • Reaction with air: Metals react with oxygen to form basic metallic oxides. Burning of magnesium ribbon in presence of oxygen produces magnesium oxides.
    • Reaction with water: Some metals react vigorously with water, Example: Sodium. There are other metals which react slowly with water, example: iron. Apart from these metallic oxidesare easily dissolved in water and form alkalis.
    • Reactions with Acids: Metals are generally reactive with acids and produces hydrogen gas, more reactive metals displace the hydrogen from its dilute acid form metallic salt and hydrogen gas which makes a popping sound.
    • Reactions with Bases: Some Metals react with bases. Example: 2NaOH(aq.)+Zn(s)→Na2ZnO2(aq.)+H2(g).
  • Displacement reaction:

Metals have the capability to displace another less reactive metal in aqueous environment. The product of such a reaction is salt solution

Example:

i) Copper Sulphate (CuSO4) + Zinc (Zn)→Zinc Sulphate (ZnSO4) + Copper (Cu)

ii) 2Al(s)+Fe2O3(molten)→Al2O3(s)+2Fe(molten)

Uses:

  • Metals are used in making heavy machinery, automobiles, Aeroplan’s, trains, satellites, industrial gadgets, cooking utensils, water boilers, etc.
  • Metals are used to make electrical wires and heigh in tensile strength metal sheets.
  • Aluminum foils are used in packaging medicines, cigarettes and food materials.
  • Silver and gold are used to make jewelry, coins etc.

2) Non- metals

i) Definition: Non-metals are those compound’s which do not have the attributes of metals.

ii) Examples: Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, Iodine, Carbon, Sulphur, Silicon etc.

iii) Physical Properties:

    • Poor conductor of heat and electricity (except graphite) and can act as insulators.
    • They are non- malleable and non-ductile.
    • They are soft, brittle and appear dull i.e., they lack luster.
    • They are not sonorous
    • They are converted into a powder like material wen struck with a hard object
    • They can occur in any state of matter viz. solid, liquid or gas

iv) Chemical properties:

  • Reaction with air: Generally, oxides of non-metals are acidic in nature. Example: Sulphur dioxide (SO2) + Water (H2O) ® Sulphurous acid (H2SO3)
  • Reaction with water: Generally, non-metals do not reactwith water. This is why non-metals arestored in water. An example isphosphorus is a very reactive non-metal. To prevent contact of phosphorus withatmospheric oxygen, it is stored in water.
  • Reactions with acids: They do not react with acids.
  • Reaction with Bases: Such reactions are complex

 v) Uses:

    • Non-metal is essential for our life which all living beings inhale during breathing,
    • Non-metals used in fertilizers to enhance the growth of plants.
    • Non-metal used in water purification process.
    • Non-metal like iodine is applied on wounds as an antiseptic.
    • Non-metals used in crackers.

Materials Metals and Non Metals Class 8 Notes PDF

Metarials Metals and Non Metals Class 8 Notes

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