Materials: Metal And Non-metals

(1) Iron – It is used to make doors and windows.

(2) Copper – It is used to make electric wires.

(3) Gold – It is used to make ornaments.

(4) Silver – It is also used to make ornaments.

Materials can be divided as metals and non-metals. Metals can be separated on the basis of physical and chemical properties.

Physical properties – Ductility, Malleability, Lustre and Hardness are physical properties.

Chemical properties –

(i) Metals on reaction with oxygen form basic oxides while non -metals on reaction with oxygen form acidic oxides.

(ii) Metals react with water but non-metals do not react with water.

(iii) Metals react with acids and produce hydrogen gas but non-metals do not react with acids.

(iv) Metals react with bases and produce hydrogen gas but reactions of non-metals with bases are complex.

Iron, Copper and Aluminium are metals because these are hard and lustrous but Sulphur, Nitrogen and Oxygen are non-metals.

We cannot hold hot metal pan directly because metals are good conductor of heat and they hurt us. So we use plastic or wooden handle to hold the hot metal pan because plastic and wood are bad conductor of heat and they do not hurt us.

Connecting wires are made up of copper and aluminium because these metals are ductile and good conductor of electricity.

We don’t use non-metals for making jewellery because non-metals are not lustrous. We use metals for making jewellery because they are lustrous.

Diamond is a non-metal which is very hard. Diamond is an allotrope of carbon.

Metal oxides are basic in nature while non-metal oxides are acidic in nature.

When metals react with dilute acids then hydrogen gas is produced. This hydrogen gas burns with a pop sound.

Na + dil.HCl→ NaCl + H₂

When sulphur dioxide reacts with water then sulphurous acid (H₂SO₃) is produced.

SO₂ + H₂O→ H₂SO₃

When magnesium reacts with oxygen then magnesium oxide (MgO) is produced. Magnesium oxide is basic in nature.

Note- Oxides of metal are basic in nature while oxides of non-metals are acidic in nature.

Gold and silver are used to make ornaments.

No. Copper cannot displace zinc from its salt solution because copper is less reactive than zinc. More reactive displaces less reactive metal from its salt solution.

When copper sulphate reacts with zinc then zinc displaces to copper and zinc sulphate is formed because zinc is more reactive than copper. So the blue colour of copper sulphate disappears and a powdery red mass of copper is deposited at the bottom of the beaker. Hence the colour of the solution formed is red.

CuSO₄ (Blue) + Zn→ ZnSO₄ (colourless) + Cu (Red)

Yes, Sulphur dioxide is acidic in nature because oxides of non-metal are acidic in nature.

Copper and aluminium are used for making cooking utensils and water boilers for factories.

Zinc is used to galvanise iron to protect it from rusting.

The physical properties on the basis of which metals can be distinguished from non-metals are:

(i) Hardness- Metals are hard while non-metals are soft.

(ii) Lustre- Metals are lustrous while non-metals are not lustrous.

The oxides of metals are basic because they dissolve in water to form metal hydroxides which are basic in nature. These metal hydroxides release OH^- ions. So they are basic in nature.

Iron can react with steam because iron is less reactive so it reacts with steam.

Pencil lead is made up of graphite.

Bromine is a liquid non-metal.

Metals are sonorous. Sonorous means metals make noise on striking with another metal. So bells used in temples are made up of metals and not of wood which is a non-metal.

Heated iron + steam→ ferrous ferric oxide + Hydrogen gas

3Fe + 4H₂O→ Fe₃O₄ + 4H₂

Phosphorus is a very reactive element. It catches fire spontaneously in air. But it is insoluble in water so it is kept in water.

(a) When metals combine with oxygen then metal oxides are formed which are basic in nature because they dissolve in water to form metal hydroxides which are basic in nature. These metal hydroxides release OH- ions.

(b) When non-metals combine with oxygen then non-metal oxides are formed which are acidic in nature because these react with water to form acids or with bases to form salts.

Copper cannot displace zinc from its salt solution because copper is less reactive than zinc. More reactive metal displaces less reactive metal from its salt solution.

(a) (i) Malleability- Malleability is a property of metals in which metals can be beaten into sheets.

Example- Gold and aluminium

(ii) Ductility- Ductility is a property of metals in which metals can be drawn into wires.

Example- Copper

(b) Diamond is a non-metal which is very hard. Diamond is an allotrope of carbon.

(a) Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and so metals conduct heat.

(b) Metals are sonorous. Sonorous means metals make noise on striking with another metal but non-metals do not make noise on striking. So non-metals cannot be used for making bells.

Uses of metals are

(i) Metals are used in making machinery and automobiles.

(ii) Metals are used in making aeroplanes and trains.

(iii) Metals are used in making satellites.

(iv) Metals are used in making industrial gadgets.

(v) Metals are used in making cooking utensils and water boilers.

Uses of non-metals are

(i) Non metals are used in fertilisers to enhance the growth of plants.

(ii) Non metals used as a food preservative.

(iii) Non metals used in respiration.

(iv) Non metals used in firecrackers.

(v) Non metals used in water purification process.

(i) When metals come in contact with air and water then rusting takes place. In iron, rusting is a process in which iron is oxidised into ferric oxide (Fe₂O₃).

(ii) The presence of impurities in the iron like water vapours, acids, salts and carbon dioxide also responsible for rusting.

(iii) Iron does not rust in pure water which is free from dissolved salts.

(iv) Metals like chromium, zinc and magnesium prevent rusting. So zinc is used to galvanise the iron to prevent rusting of iron.

(i) Sodium reacts vigorously with cold water and a large amount of heat releases but iron reacts with steam very slowly.

(ii) Sodium metal reacts with ferric oxide (Fe₂O₃) and forms sodium oxide by displacing iron.

6Na + Fe₂O₃ → 3Na₂O + 2Fe

(iii) Sodium reacts with acids very quickly but iron takes some time to react with acids.

When a piece of sodium is dropped in water then it reacts vigorously with water to form sodium hydroxide with the evolution of hydrogen gas in the form bubbles. This hydrogen gas catches fire and a large amount of heat releases. This is a highly exothermic reaction. The solution will be basic in nature because sodium hydroxide is formed.

2Na + 2H₂O→2NaOH + H₂