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Class Notes

Class: 8th Topic: Metals & Non Metals ( Notes to be learnt. Definitions can be written)

Subject: Science

All elements can be divided into 2 main groups- METALS & NONMETALS. There is another group of elements called METALLOIDS. A metalloid is an element that has properties intermediate between those of metals & non metals. Some eg. of metals , Nonmetals & metalloids with their symbols are given below- Metals Non metals Metalloids Copper-Cu Oxygen- O silicon – Si Iron - Fe Nitrogen – N Boron - B Aluminium - Al Sulphur – S Germenium - Ge

Physical properties of Metals & Non metals

Malleability – It is the property by which they can be beaten into thin sheets.

Ductility- The property by which they can be drawn into wires is called ductility.

Sonorous – Metals make a ringing sound when struck against any hard object. This property is called sonority.

Lusture- Metals have a shiny appearance called Lusture.

Chemical properties of metals & non metals

Reaction with Oxygen – Metals react with oxygen to form metal oxides which are basic in nature.

Mg + O2 ----------- MgO (magnesium) ( oxygen) (Magnesium oxide)

Fe + O2 + H2O ---------- Fe2O3

(Iron) ( oxygen) (water) ( Iron oxide)

Non metals react with oxygen to form non metallic oxide which are acidic in nature.

S + O2 ------------- SO2

(Sulphur ) (Oxygen) ( sulphur dioxide)

Reaction with Water - Metals react with water to form metal hydroxide & hydrogen gas. Some metals react vigourously even with cold water (eg- sodium) , some react with hot water (Mg) & some react with steam ( zinc, iron)

Na + H2O --------- NaOH + H2 (sodium) (water) ( sodium hydroxide) (hydrogen)

Hydrogen gas burns with a “pop” sound when a lighted matchstick is brought near the mouth of test tube.

Non metals generally do not react with water though they may be very reactive in air. Such non metals are kept under water eg. Phosphorous is a very reactive nom metal. It catches fire if kept open in air. So it is kept in water.

Reaction with Acids

Most of the metals react with dilute acids to form salts & hydrogen gas.

Metal + Acid ------ Salt + Hydrogen gas

Only less reactive metals like copper , silver& gold do not react with dilute acids.

Generally Non- metals do not react with acids.

Reaction with bases

Some metals react with bases to form salts & hydrogen gas.

Metals + Bsaes ------ Salt + Hydrogen gas

Reaction of non metals with bases are complex.

Chemical properties of metals & non metals

Reaction with Oxygen – Metals react with oxygen to form metal oxides which are basic in nature.

Mg + O2 ----------- MgO (magnesium) ( oxygen) (Magnesium oxide)

Fe + O2 + H2O ---------- Fe2O3

(Iron) ( oxygen) (water) ( Iron oxide)

Non metals react with oxygen to form non metallic oxide which are acidic in nature.

S + O2 ------------- SO2

(Sulphur ) (Oxygen) ( sulphur dioxide)

Reaction with Water - Metals react with water to form metal hydroxide & hydrogen gas. Some metals react vigourously even with cold water (eg- sodium) , some react with hot water (Mg) & some react with steam ( zinc, iron)

Na + H2O --------- NaOH + H2 (sodium) (water) ( sodium hydroxide) (hydrogen)

Hydrogen gas burns with a “pop” sound when a lighted matchstick is brought near the mouth of test tube.

Non metals generally do not react with water though they may be very reactive in air. Such non metals are kept under water eg. Phosphorous is a very reactive nom metal. It catches fire if kept open in air. So it is kept in water.

Reaction with Acids

Most of the metals react with dilute acids to form salts & hydrogen gas.

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