CH-4 MATERIALS: METALS AND NON-METALS //important notes//Ak Raj..

CH-4

    MATERIALS: METALS AND NON-METALS

Important notes:-

4.1 PROPERTIES OF METALS AND NON-METALS:-

There are two types of properties:-

• Physical properties
• Chemical properties

Physical properties of metals:-

• Metals are solid, except mercury that is found in liquid states at room temperature.
• They are hard and tough except sodium and potassium that can be cut with knife.
• They are lusterous i.e. they shine in light because metals posses free electrons that vibrates on getting in contact with light.
• They have high melting points except caesium and gallium hane a low melting points..
• They are conductors of heat and electricity. The best conductor of electricity are silver and copper whereas, lead and mercury are comparatively poor conductors.
• They have high density except alkali metals like lithium, sodium and potassium.
• They are malleable. They can be beaten into thin sheets.
• They are ductile. They can be drown into wires.
• They are sonorous. They produce a singing sound when struck against a hard object.
• Examples:- Iron, Gold, Silver, Copper, Magnesium, Aluminium nad many more.

Physical properties of non-metals:-

• Non-metals may be either, solids, liqid or gases.
• Solids non-metals are brittle and break down into powdery mass on striking with a hammer, except Diamond which is the hardest non-metals.
• They have a dull luster but iodine is  a lusterous.
• They have low melting points except diamond that has very high melting point.
• They are poor conductor of heat and electricity, except graphite.
• They are not malleable.
• They are not ductile.
• They are not sonorous.
• Examples:- Carbon, Sulpher, Oxygen, phosphorous and many more.

4.2 CHEMICAL PROPERTIES OF METALS AND NON-METALS

Reaction of matals with oxygen:-

• Metals reacting with oxygen is observed in our day to day life. We are must have observed rusting of iron, silver jewellary getting tarnished or copper articles getting covered by green layer. Metals reacts with atmospheric oxygen and produces metaloxides that are basic in nature because they react with water to form basic.
• In case of rusting of iron , the iron reacts with the oxygen present in air nad moisture and develops rust (hydroted iron (III) oxide)

4Fe  + 3O2 + 2H2O  ------------------------>  2Fe2O3H20

Iron + Oxygen + Water    -----------------> Rust

• In case of rusting of copper, the metalic copper reacts with oxygen, carbon-dioxide and atmospheric moisture and develops a green coloured coating of copper hydroxide and copper carbonate.

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

    Copper + Water + Carbon-dioxide + Oxygen ----> copper hydroxide + copper carbonate

• In case of tarnishing of silver articles, the metallic silver reacts with hydrogen sulpheride or sulpher present in air  gets tarnished.

4Ag + 2H2S  + O2  -------------> 2Ag2S  + 2H2O

Polished silver         Tarnished silver

• Copper burns in air to combine with oxygen and form copper (II)oxide, a black oxide.

2Cu + O2 -------------> 2Cuo

Copper + Oxygen---------------> Copperoxide

Reaction of metals with water:-

• Sodium being very reactive, it reacts vigorously with water leading to the production of sodium hydroxide and hydrogen. Therefore it is stored in kerosene.

2Na + 2H2O------------>2NaOH+ H2

Sodium + Water--------------> Sodium hydroxide + Hydrogen

• Magnesium undergoes reaction with water to form magnesium hydroxide and hydrogen.

Mg + H2O  -------------------> Mg(OH)2   +  H2

• Iron reacts very slowly with water .

3Fe + 4H2O  ---------------> Mg(OH)2 + H2

Reaction of metals with acids:-

• Metals reacts with acids to produce hydrogen gas. If a matchstick is brought near the product of all the reaction then we hear a pop sound. It is this hydrogen gas that burns with pop sound.
• Magnesium reacts with dilute hydrochloric acids to form magnesium chloride and hydrogen.

Mg + 2Hcl  --------------> MgCl2  + H2

• Copper does not react with hydrochloric acid but reacts with sulphuric acid.

CuO + H2SO4  ----------------> CuSO4 + H2O

Reaction of metals with bases:-

• Metals react with sodium hydroxide to produce hydrogen gas.
• Zinc reacts with sodium hydroxide to give sodium zincate.

Zn + 2NaOH -------> Na2 ZnO2 + H2

Reaction of non-metals with oxygen:-

• Non-metals reacts with oxygen to produce non-metallic oxides that are acidic in nature because when dissolved in water non-metallic oxides gives off non-metallic acids.
• Sulphur reacts with oxygen producing sulphur dioxide which on further reaction with water gives sulphurous acid.
• S + O2 -----------> SO2
• SO2 + H2O -> H2SO3

Reaction of non-metals with water:-

• Non-metals do not react with water but are very reactive in air due to which they are stored in water. Phosphorous is a vigorously reacting non-metals that catches fire if exposed  in air. To avoid such reaction phosphorous is stored in water that cuts off its contact with atmospheric oxygen.

Reaction o fnon-metals with acids:-

• Non-metals do not react withj acids. This is due to the fact that a substance undergoing reaction with acids donates electronsto the H+ ions produced by the acids. But non-metals are acceptor of electrons and hence, They do not donate electron to the hydrogen ions of the acid. As a result they do not react with dilute acids. But they are some exceptions:-

6HNO3  + S  -------->  H2SO4  + 6NO2  + 2H2O

Reaction of  non-metals with bases:-

• Reaction of non-metals with bases are quite complex. They react with base to form salt.
• reaction of calcium hydroxide  and chlorines gives bleaching powder.

Ca(OH)2  + Cl2  ------------->  Ca(OCl) + H2O

Displacement reactions:-

• In displacement reaction a more reactive metal displaces a less reactive metal but a less reactive metal cannot displace a more reactive metal.
• Let us take 5 beakers.

• In beaker A Zn being more reactive than copper replaces copper from the solution of copper sulphate and forms zinc sulphate.
• CuSO4 + Zn -----------------> ZnSO4 + Cu
• In beaker B iron being more reactive than copper replaces it from its solution and forms iron sulphate.
• CuSO4 + Fe ----------------> FeSO4 + Cu
• In beaker C there would be no reaction as less reactive metal (copper) cannot displace more reactive metal (zinc) from its solution.
• In beaker D there would be no reaction as less reactive metal (copper) cannot displace more reactive metal (iron) from its solution.
• In beaker E there would be no reaction as less reactive metal (iron) cannot displace more reactive metal (zinc) from its solution.

4.3 USES OF METALS AND NON-METALS

Uses of metals

• Metals being hard, tough are used in manufacturing automobiles, machinery, trains, satellites, aeroplanes, industrial gadgets.

• Due to its characteristic of being a good conductor of electricity and ductility it is used in making wires, electrical appliances, circuits and many more.
• Being a good conductor of heat it is used in making utensils, water boilers.

Uses of non-metals:-

• Non-metal is the basic requirement of life. Oxygen is inhaled while breathing.
• Nitrogen is used in fertilizers to enhance the fertility of soil.
• Chlorine and fluorine are used for water purification.
• It is used as an antiseptic and applied on wounds.
• It is used as disinfectant.
• It is used in crackers.

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• AK Raj..