Class 8 Metals and Non Metals

CH-4 Materials: Metals & Non metals

1. Define Matter?

• Anything that occupies space and has mass is called Matter.
• Ex: chair, car, train etc.

2. Define Element?

• Element is a substance that cannot be split up into two or more simpler substances by chemical methods that is applying heat, light, electric energy.
• Ex: Iron, Oxygen , Magnesium etc.

3.How are Elements classified?

• Elements are classified into Metals, Non Metals, Metalloids.
• Metals = Metals are hard and Shiny in appearance Ex: Iron, copper, tin, gold etc.
• Non metals = Non metals are not so hard, they are mostly dull appearance. Ex: Sulphur, Phosphorus, Hydrogen, Oxygen, Nitrogen, Carbon etc.
• Metalloids – Some elements have certain properties of metals and certain properties of nonmetals. These are known as Metalloids. Ex: Arsenic, Antimony, Germanium etc.

4. Define Ores?

• Earth’s crust is the main source of Metals and Non metals.
• Minerals from which metals extracted conveniently and profitably are called as Ores.

5.What is Gangue ?

In Ores, there are certain impurities present along with metallic minerals. These impurities are called as Gangue.

6.Define Metallury ?

The series of processes carried out to extract pure metals from their ores is called Metallurgy.

Ex: Some Important Ores are

• Bauxite – A1₂0₃. H₂0
• Iron pyrites = FeS₂
• Haematite = Fe₂O₃.2H₂O
• Copper glance = CUS

7. Occurrence:

i) Metals = It exist both in combined State and free state.

• Combined state = Iron copper.
• Free state = Gold, platinum etc
• Na, K, ca = found in sea water

ii) Non Metals – It exist both in combined state and free state.

• Combined state – Oxides, Carbonates, Phosphates.
• Free State – oxygen in atmosphere.
• Oxygen is present in combined State in water.

Physical properties of Metals and Non Metals:

1. Physical State:

• Metals = Metals exist as solid at room temperature Ex: Gold, aluminium.
• Metals exist as liquid. Ex. Mercury
• No metals exist in gaseous state.
• Non metals: Non metals exist as Solid or gaseous.
• Ex: Solid = Sulphur, phosphorous, carbon
• Gas – H₂, O₂, N₂ are gases.
• Bromine is the only non metal that exist as liquid at room temperature.

2. Malleability & Brittleness.

Property that allows the metals to be Hammered into thin sheets or foils is called Malleability

Metals – Metals are Malleable. Ex: Gold, Silver, aluminium, copper.

Ex: Aluminium foils are used for safe packing of foodstuff, medicine, chocolates etc.

Non metals – Non metals are non Malleable, they cannot be breaken into pieces, they are broke down into pieces.

Brittleness – Property due to non metals break up into pieces on hammering is called Brittleness.

Non metals are generally brittle

Ex: Sulphur, coal break up into small pieces on hammering.

3. Ductility:

• The property that allows the metals to be drawn into thin wires is called Ductility.
• Ex: Gold, Silver, Copper, aluminium, iron etc.
• Non metals are not ductile.
• Ex: When Stretched non metals like Sulphur, Phosphorus break into pieces and do not form wires.

4. Lustre:

Metals:

Metals are lustrous that is they have shiny surface. It makes them good reflectors of light. Ex: Gold, Silver, platinum. They are used for making Jewellery decorative articles.

Non Metals:

Non metals show dull appearance. Some Non metal iodine, graphite show some lustre.

5. Conductivity of Heat:

• Metals –  They are good conductors of heat. Ex: silver, copper, iron, aluminium. They are used for making utensils, water broilers etc.
• Non metals are poor conductor of heat. Ex: Diamond is a only non metal that is a good conductor of heat.

6. Hardness:

• Metals – Metals are hard. Ex: Iron metal is hard and strong.  Iron metal is used in construction of bridges, railway station etc.
• Sodium, potassium are Soft metals that can be easily cut into knife.
• Non metals are not hard or strong. Diamond  is the ONLY  hardest naturally occuring substance

7. Tensile Strength:

The property that allows a substance to bear lot of strain without breaking is called Tensile strength.

Metals have high tensile strength. Ex: Iron, but zinc has low tensile strength.

Non metals have low tensile strength, so they break easily, Carbon has high tensile strength

8. Density:

• Metals = Metals have high density but Na, k has low density.
• Non metals – Non metals have low density and soft but diamond has high density.

9.Conductors of electricity:

• Metals  – They are good conductors of electricity. Ex: copper, aluminium, silver.
• Non metals – They are poor conductors of electricity
• Ex: Sulphur, phosphorous. Graphite is a non metal that is good conductor of electricity.

10. Sonority:

• The property of producing ringing sound by metal when it strikes with hard material is called Sonority.
• Metals are Sonorous.
• Non metals are Non Sonorous.

11. Melting and Boiling point:

Metals = They have high melting and boiling point.

Ex: Iron has a melting point 1535°C. However, Na, K, Hg, Gallium have low melting point.

Non metals have low melting and boiling point

Ex: Melting point of sulphur is 115°C. However, Diamond has very high melting point.

Chemical properties of Metals and Non metals:

Reaction with 0₂:

Metals react with 0₂ to form metal oxides that are basic.

• Mgo + H₂0 ———> Mg (OH)₂

                             (Magnesium Hydroxide)

• 4 Na + 0₂ ——–>2 Na₂O
• 2Zn + 0₂ ——–> 2Zn0

2. Non metals act with 0₂ to form acidic oxides

• S+ 0₂ ——-> S0₂ Sulphur dioxide
• S0₂ +H₂0 ——–> H₂S0₃ (sulphurous acid)
• C + O₂ ——-> CO₂
• CO₂ + H₂0 ———> H₂C0₃ (carbonic acid)
• 2N₂ + 0₂ ——-> 2N₂O (Nitrous oxide)

Exception: Metals like gold is unreactive, It does not react with air, water vapour, other gas in atmosphere so gold ornaments look “New” after years.

2. React with water:

Metals

Metals react with water and displace H₂ from water to form metal hydroxide ,

metal oxide, H₂ gas. Some metals react with cold water, some with hot water

1. 2K +2H₂0 ——–> 2KOH + H₂ () + Heat

cold

water

2. Mg + H2O ——–> Mgo + H₂

(Boiling water/steam) Magnesium

                                     oxide  Gas

3. Zn + H₂0  ——-> ZnO +H₂

                                  Zinc

                                   Oxide

Non Metals:

• Non metals do not react with water/steam.
• Copper, gold, silver, platinum do not react with water.
• They are used to make decorative items, coin, ornaments, Platinum is used to make alloys, electronic gadgets.

3. Reaction with acids:

Metals react with acids to form Salt and H₂ gas.

1. Zn +H₂SO₄ ——–> ZnSO₄ + H₂

2. Mg + H₂S0₄ ——–> MgS0₄ + H₂

Dilute HCl.

1. Mg + 2HCl ——–> MgCl₂ + H₂

2. 2Al +6HCl ———> 2AlCl3 + 3H₂       

                                      Aluminium

                                        Chloride

3. Fe + 2HCl ——-> FeCl₂+ H₂

4. Cu + HCl ——-> No reaction.

Non metals do not react with dilute HCl ( Ex: Coal, Sulphur)

Reaction with Bases:

Metals react with bases to form respective salt and form H₂ gas.

2Al +2NaOH + 2H₂O —–> 2NaAl0₂ + 3H₂

                                                 Sodium

                                                aluminate

Reaction of bases with Non metals is slightly complicated.

Displacement reactions:

It is the chemical reaction in which more reactive element displaces less reactive element from its compound (salt solution)

Ex: Fe + CuSO₄ ——> FeSO₄ + Cu

       Grey    Blue             Green    Reddish         

                                                      Brown

CUSO₄ + Zn ——-> ZnSO₄ + Cu

Blue                         Colourless Reddish Brown 

CuSO₄ + Mg ——-> MgS0₄ +      Cu

 Blue                          Colourless Reddish

                                                       Brown

FeSO₄ + Zn ——–> ZnSO₄ + Cu

 Green                    Colourless Reddish

                                                  Brown

Non metals: Most of the Non metals do not show displacement reactions. But more reactive Non metals displace less reactive ones.

Ex:

2KBr + Cl₂ ——-> 2KCl + Br₂

Potassium            Potassium

Bromide               Chloride

Uses of Metals:

• Copper is used for making electrical wires, cables, since it is good conductor of electricity. It is used to make alloys, utensils, car radiators.
• Iron = Pig Iron is hard and brittle used to make pipe, storage tank, sink.
• Wrought Iron is tough malleable used to make belt, chain, nail, agricultural tools.
• Stainless steel (alloy of Iron) used to make utensils, Knives.
• Aluminium used to make utensils, paint, body parts of aircraft.
• Gold, Silver, Platinum used to make Jewellery, decorative items. Platinum used to make electrolytic cells
• Lead used to make electrodes for automobile batteries.
• Chrominum used  for electroplating.
• Zinc used in dry cells, galvanisation (coating Iron particles to prevent rust)

Uses of Non Metals:

• Carbon is used in the form of graphite is used to make pencil lead, lubricants,. electrodes in dry cells etc.
• Carbon in form of diamond used to make Jewellery. It is used for cutting and grinding.

• Sulphur is used to make skin ointment, manufacture of dyes, gunpowder, firework, H₂S0₄. It is also used as fungicide, insecticide.
• Iodine is used to prepare salt.
• 0₂ for respiration and combustion.
• Phosphorus for phosphate fertiliser, phosphoric acid and rat poison.
• Nitrogen is used for Manufacturing NH₄,  HNO₃, fertiliser.
• Chlorine is used for disinfecting water, manufacture of bleaching powder, PVC, plastics, pipes
• Hydrogen is used in extraction of metals such as Copper, lead , tin and
• also used to manufacture ammonia gas.

Define Corrosion?

The process in which metal is reacted by the action of air, moisture or chemical on their surface is called Corrosion.

Ex: Iron, copper, silver.

How Iron objects / Define Rusting of Iron?

when Iron object is left for a considerable

time in a place where there is high moisture, it result in the formation of reddish brown flaky substance on called Rusting of Iron.

Iron + O₂ + H₂0 ——-> Hydrated Iron Oxide

                                               Reddish Brown. This is called Rust.

How Copper reacts with Moisture?

When copper is left for a long time in a moisture place it reacts with CO₂ & H₂0 to form green coating of Copper hydroxide and Copper carbonate. It loses its Shine.

2Cu+ O₂ + H₂O + CO₂ ——-> Cu(OH)₂ + CuCO₃

How Silver objects react with moisture ?

When silver objects are kept in air, they get tarnished and turns black. Silver reacts with H₂s in air to form a thin silver sulphide on its  surface.

How to prevent Corrosion?

• Oil, grease or paint is applied on the the metal away from grease air & moisture.
• Zoating on Zinc  on the surface of Iron object. This is called galvanisation.
• A layer of another metal deposited on surface of metal object by electroplating.
• Uniform protective layer of aluminium oxide is formed on aluminium object by process of anodising.
• Some other metals/ Non metals are mixed with metal objects to create alloys.

Alloy

A homogenous mixture of two or more metals  along with non metals 

is known as alloy.

Characteristics of alloys.

• Alloys are hard.
• They are resistant to corrosion.
• They have high tensile strength.
• Some have low melting point.

Uses of alloys.

1. Carbon added to Iron increases its hardness. It is used to construct ship, bridge, vehicles.
2. Stainless steel – Iron, chrominum, nickel combination is Stainless Steel. It is used to make surgical instrument, cutlery.
3. Chrome steel – Combination of Iron & chrominium used to make axle, cutting tools.
4. Solder – Alloy made by combining tin and lead. It is used for joining electrical wires.
5. Brass combination of Copper and Zinc. It is malleable and resistant to corrosion. It is used to make utensils, screw, bolt
6. Bronze- combination of copper and tin. very strong highly resistant to corrosion. used to make Statues, medals, coins.
7. Duralumin – combination of Al, Cu, Mg, Mn, strong resistant to corrosion.  It is used to make parts of automobiles, pressure cooker. It is light and ductile.
8. German Silver – Combination of Cu, Zn, Ni, Resistant to corrosion and shines like Silver. It is used to make resistance wires and electroplating.

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