METALS AND NON METALS Notes for class 8

Class 08 CHAPTER -4    MATERIALS : METALS AND NON METALS

1) Occurrence of metals and non metals :-

Out of the 92 naturally occuringelements 70 are metals and about 22 are nonmetals. 

Some elements show properties of both metals and non metals. They are called metalloids.

•Only some metals like gold, silver, platinum etc are found in the free state. Most metals are found in the combined states as oxides, sulphides, carbonates, silicates etc.

•Some non metals are found in the free state like helium, neon, argon etc. and some are found in free and combined states like sulphur, phosphorus etc.

2) Metallurgy :-

•Metallurgy:-is science of extraction of metals from their ores and their purification.

•Minerals:-are naturally occuringsubstances containing one or more elements or their compounds.

•Ore:-is a mineral from which one or more metals can be extracted profitably.

•Metallurgical processes:-consists of three main steps. They are :-i) Concentration of the ore ii) Reduction iii) Refining

•Concentration of the ore:-is the removal of impurities from the ore.

•Reduction:-the process of obtaining the metal from its compound.

•Refining:-is the process of purification of the impure metals to obtain the pure metal.

3) Physical properties of metals and non metals:-

•Metals

•Metals are solids (except mercury).

•Metals are hard (except sodium, potassium etc.

•Metals have metallic lustre.

•Metals have high melting points and bolilingpoints.

•Metals are malleable ( can be made into thin sheets).

•Metals are ductile (can be made into thin wires).

•Metals are good conductors of heat and electricity.

•Metals are sonorus(produces sound).

•Non metals

•Non metals may be solids, liquids or gases.

•Non metals which are solids are brittle (diamond is the hardest).

•Non metals do not have lustresome have a dull luster.

•Non metals have low melting points.

•Non metals are not malleable.

•Non metals are not ductile.

•Non metals are bad conductors of heat and electricity (except graphite).

•Non metals are not sonorous

4) Chemical properties of metals and non metals:-

a) Reaction with oxygen:-

Metals react with oxygen to form metallic oxides. These oxides are  basic oxides because they react with water to form bases. Eg. Magnesium burns in air to form magnesium oxide. Magnesium  reacts with water to form magnesium hydroxide.

2 Mg + O2--à2 MgO

MgO+ H2O-à  Mg(OH)2

Non metals react with oxygen to form non metallic oxides. These  oxides are acidic oxides because they react with water to form  acids.

Eg. Sulphurburns in air to form sulphurdioxide. Sulphurdioxide  reacts with water to form  sulphurousacid.

S + O2->SO2

SO2+ H2O---> H2SO3

b) Reaction with water:-

Metals react with water to form metal hydroxides and hydrogen.

Eg. Sodium reacts with water to form sodium hydroxide and  hydrogen.

2 Na + 2 H2O--> 2 Na OH + H2

Magnesium reacts with water to form magnesium hydroxide and hydrogen.

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

Non metals do not react with water.

c) REACTION WITH ACIDS:-

Metals react with acids to form metallic salts and hydrogen.

 Eg. Zinc reacts with dilute hydrochloric acid to form zinc chloride  and hydrogen.

Zn + 2 HCl -----> ZnCl2+ H2

Most non metals do not react with acids.

Some non metals like sulphur reacts with concentrated nitric acid to forn sulphur dioxide, nitrogen dioxide and water.

S + 4HNO3 ------> SO2+ 4 NO2+2 H2O

d) Metals replace metals:-

A more reactive metal replaces a less reactive metal from its salt  solution.

Eg. Magnesium replaces copper from copper sulphate solution to form magnesium sulphate and copper.

Mg + CuSO4---> MgSO4+ Cu

Zinc replaces copper from copper sulphate solution to for zinc sulphate and copper.

Zn + CuSO4-----> ZnSO4 + Cu

Iron replaces copper from copper sulphate solution to form iron sulphate and copper

Fe + CuSO4-----> FeSO4+ Cu

Based on the reactivity of metals, they can be arranged in the decreasing order of their activity.

5) Activity series of metals :-

The arranging of metals in the decreasing order of their reactivity is called activity series of metals.

In decreasindg order

Potassium

Sodium

Magnesium

Aluminium Decreasing

Zinc order of

Iron reactivity

Lead

Copper

Silver

Gold

6) Noble metals :-

Metals like gold, silver, platinum etc. retain their lustre because they do not react with air, water or acids. So they are called noble metals.

Gold dissolves in aqua regia. Aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid in the ratio 1:3.

Pure is 24 carat gold. It is very soft and cannot be used for making ornaments. So it is mixed with some silver or copper to make it hard.

7) Uses of metals :-

Iron :-is used for making pins, nails, nuts, bolts, tools,

machines, construction of buildings, bridges etc.

Aluminium :-is used for making utensils, wires, furniture,  parts of aircrafts, vehicles, machines, for packing food and medicines etc.

Copper :-is used for making wires, vessels, electric  gadgets etc.

Gold :-is used for making jewellery, coins medals etc

Silver :-is used for making jewellery. Coins, medals etc.

Platinum :-is used for making jewellery, electric gadgets, plugs in vehicles etc.

Sodium :-compounds are used as common salt,  chemicals etc.

Calcium :-compounds are used for making cement, glass etc.

8) Uses of non metals:-

Sulphur:-is used for making sulphuric acid, salts of  metals etc.

Oxygen:-is used for respiration by living things, burning  of fuels etc.

Nitrogen:-is used for making ammonia which is used for  making fertilizers.

Hydrogen:-is used for making ammonia which is used for making fertilizers, as fuel in rockets, for welding etc.

Chlorine:-is used to kill germs in water.

Iodine:-is used as tincture iodine which is an antiseptic

10) Corrosion:-

The surface of some metals gets corroded when exposed  to moist air for a long time. This is called corrosion.

Prevention of corrosion of metals:-

The corrosion of metals can be prevented by:-

i) Applying oil or grease.

ii) Applying paint

iii) Galvanisation ( coating of metals with non corrosive metals like zinc)

iv) Electroplating ( coating of metals with non corrosive metals like chromium tin by passing

electricity)

v) Alloying ( Eg. When iron is alloyed with chromium and nickel, it forms stainless steel which is resistant to corrosion) 

CCE :Class VIII :Metal and Non Metal : Fill in the blanks

CCE :Class VIII :Metal and Non Metal : Fill in the blanks

1. ---------- is liquid  metal

(mercury)

2. ------ , -------------- and     ----------- are soft metal

(Lithium, Potassium, Sodium)

3.    ------------ and  ------------ are have low melting points. They melt in the palm of the hand

(Gallium and Ceasium)

4. Metals can be beaten into thin sheets so they are called     ----------------

(malleable)

5. ---------- is only liquid Non metals

(Bromine)

6.  -------------- is the hardest natural substance

(diamond)

7. Non metals are bad conductors of electricity  except -------------

(graphite)

8. Metals react with oxygen to form ---------- oxides (Basic)

9. Some metal oxides show acidic and basic properties. They are called ---------. Eg :- Aluminum oxide, Zinc oxide etc.

(amphoteric oxides)

10. Al2O3  +  6HCl    ------à ----------  +  3H2O

(AlCl3)

11.    Al2O3  +  NaOH     -------à --------    +  H2O

(NaAlO2)

12. -------------- and  ---------does not react with oxygen even at high temperature.

( Silver, gold)

13. Metals like potassium and sodium react vigorously with oxygen and catch fire if kept in open. Hence they are stored in ------------ to prevent burning.

(kerosene)

14. Magnesium reacts only with ---------- water to form magnesium hydroxide and hydrogen.

( hot)

15. Metals like aluminium, iron and zinc react only with  ----  to form the metal oxides and hydrogen. (steam)

16.  --------  gas is not evolved when metals react with nitric acid (HNO3) because it is a strong oxidising agent

(Hydrogen)

17. A more reactive metal displaces a ------- reactive metal from its salt solution

(less)

18. The arranging of metals in the decreasing order of their reactivity is called  -----------series of metals.

( reactivity)

19. Metals lose electrons and become positive ions. So they are called ------elements

(electropositive)

20. Non metals ----- electrons and become negative ions. So they are called electro negative elements

(gain)

21. ----------are compounds formed by the transfer of electrons from a metal to a non metal(Ionic compounds)

22. If one of the metals in an alloy is mercury, it is called an  -------

( amalgam)

23. ---------is the damage caused to metals due to the reaction of metals with oxygen, moisture, carbon dioxide etc.

(Corrosion)

24. Some elements show properties of both metals and non metals. They are called -----

(metalloids)

25. -------------is a mixture of concentrated nitric acid and concentrated hydrochloric acid in the ratio 1:3.

( Aqua regia)

CBSE Extra score Notes for: Metals and Nonmetals for VII Science

Metals : The elements that lose electrons and form positive ions are called metals. They are also called electropositive elements. E.g. sodium, potassium, calcium, magnesium, gold, silver, copper, etc.

Hydrogen is a nonmetal but it is placed in the in the group of metals because like metals it also loses electron and forms positive ion.

Physical properties of metals:

Metals are malleable, ductile, hard, good conductors of heat and electricity, and sonorous. They are generally solids and have high melting and boiling points.

Lusture :  The property of an element due to which it has a shiny appearance is called metallic lusture.

Malleability  The property of metals to be beaten into thin sheets is called malleability. Gold and silver are most malleable metals.

Ductility  The property of metals to be drawn into thin wires is called ductility. Gold is most ductile metal.

Followings are exceptional Metal which –

a) Is liquid at room temperature – mercury

b) Are most malleable – gold and silver

c) Are poor conductors of heat -lead and mercury

d) Can be cut with knife – sodium, potassium,lithium

e) Is not malleable and ductile – zinc

f) Have very low melting point – gallium and caesium

g) Is most abundant in earth crust – aluminium

h) React with dil HNO3- Mg and Mn

i) Do not react with water at all – gold, silver,platinum, lead and copper

j) React with steam only aluminum, iron and zinc

k)Do not react with oxygen even at high temperature – gold, platinum, silver
Chemical properties of metals.
a) Metals on burning in air forms basic oxides.
b) Metals displace hydrogen from water and steam.
c) Metals displace hydrogen from dilute acids.
d) Metals form ionic chlorides with chlorine.
e) Metals do not react with hydrogen. ( only few reactive metals react with hydrogen to form hydrides )
Hydrogen gas does not evolve when a metal reacts with nitric acid 

because nitric acid is strong oxidising agent. It oxidises the hydrogen gas produced to water and itself gets reduced to any of nitrogen oxides i.e. N2 O, NO or NO2 .Nonmetals : The elements that gain electrons and form negative ions are called nonmetals. They are also called electronegative elements. E.g. chlorine, sulphur, oxygen, bromine, phosphorus, nitrogen, etc.
Physical and Chemical Properties  

a) Nonmetals are not malleable and ductile but they are brittle.
b) Nonmetals are solid, liquid and gas at room temperature.
c) Nonmetals are not good conductors of heat and electricity.
d) Nonmetals have low melting and boiling points.
e) Nonmetals are soft.
f) Nonmetals form acidic or neutral oxides when react with air
g) Nonmetals do not react with water and steam.
h) Nonmetals do not displace hydrogen with dilute acids.
i) Nonmetals form covalent chlorides with chlorine.
j) Nonmetals react with hydrogen to form stable hydrides.
Followings are exceptional  Nonmetals which 
a) Is liquid at room temperature – bromine
b) Are lustrous – iodine and graphite
c) Is hardest – diamond
d) Are good conductors of electricity – carbon and gas carbon
e) Is most abundant in earth crust – oxygen
f) Show allotropy – carbon, sulphur and phosphorus
g) They do not conduct electricity because they do not contain ions in molten state.
Amphoteric oxides
The metal oxides which show the properties of both acidic oxides as well as basic oxides are called amphoteric oxides. They react with both acids and bases to produce salt and water.
E.g. aluminium oxide and zinc oxide
Al2 O3 + 6HCl -----> 2AlCl3 + 3H2 O ;
Al2 O3 + 2NaOH ---> 2NaAlO2 + H2 O (Sodium aluminate)
ZnO + 2HCl ----> ZnCl2 + H2 O ;

ZnO + 2NaOH ------> Na2 ZnO2 + H2 O (Sodium zincate)

Alloy : The homogeneous mixture of a metal with other metal or nonmetal in molten state is called an alloy.
a) Stainless steel is an alloy of iron, nickel and chromium.
b) Brass is an alloy of copper and zinc.
c) Bronze is an alloy of copper and tin.
d) Solder is an alloy of lead and tin. It has low melting point and is used for welding electrical wires together.
Properties of Alloy:
a) Increase hardness ,                              b) Make resistant to corrosion,     

c) Decrease melting point,                      d) Change chemical reactivity    

e) Decrease electrical conductivity        f) Increase colour and tensile strength
Allotropy and allotropes
The phenomenon in which an element can exist in two or more different physical forms is called allotropy and the different physical forms of an element are called allotropes.Eg.  Allotropes of carbon are graphite, diamond and Buckminster fullerene.
Aqua regia. Aqua regia is the mixture of concentrated hydrochloric acid and nitric acid in the ratio 3:1. It is called ‘Royal water’ because it can dissolve gold and platinum.
Reactivity series :
The series of metals in which they are arranged in order of their decreasing reactivity is called reactivity of activity series.
Reactivity  : The tendency of an element to attain a completely filled outermost shell by losing or gaining electrons is called reactivity.
Ionic compounds  : The compounds formed by losing or gaining electrons or by the transfer of electrons from metal to nonmetal are called ionic compounds or electrovalent compounds. Ionic bonds are formed between metals and nonmetals.E.g. NaCl, MgO, CaCl2, NaOH, Al2O3, etc.
Properties of ionic compounds
a) Ionic compounds are solids and hard because of strong force of attraction between positive and negative ions. They are brittle.
b) Melting and boiling points of ionic compounds are high because a large amount of energy is required to break the inter-ionic attraction.
c) Solution of ionic compound in water contains ions which move towards oppositely charged electrodes when electricity is passed. This is why ionic compounds are very good conductors of electricity.
f) Ionic compounds in a solid state do not conduct electricity because movement of ions in solid state is not possible due to rigid structure. So they conduct electricity only in molten state.
g) The covalent compounds are usually liquids due to the weak forces of attraction between their molecules.
h) They usually have low melting and boiling points because the force of attraction between molecules is very weak and a small amount of energy is required to break these forces.
Minerals :

The elements and compounds which are found naturally in the earth crust are called minerals.Ores  The minerals from which metals can be extracted easily and profitably are called ores. An ore contains good percentage of metals and less impurities.
Rusting:. The process of depositing a brown flaky substance on the surface of iron due to air and moisture is called rusting. The brown substance is called rust. It is chemically Fe2O3.xH2O.
The process of depositing a thick layer of zinc metal on iron objects is called galvanization.
Chrome plating. 
The process of depositing a layer of chromium (Cr) on iron objects is called chrome plating.
Alloying. 
The process of making homogeneous mixture of a metal with other metal or nonmetal in molten state is called alloying.

 All ores are minerals but all minerals are not ores because there may be some minerals from which metals cannot be extracted easily and profitably.
Gangue :  The unwanted materials or the impurities like soil and sand present in an ore are called gangue.
Corrosion. : The process of slowly eating away of metals due to their conversion into oxides, carbonates, sulphides, sulphates, etc by the action of moisture and gases is called corrosion

Conditions for rusting are – presence of moisture and presence of air.
Prevention of rusting : Rusting of iron can be prevented

a) by painting, applying grease or oil,

b) galvanization,

c) chrome plating,

d) anodizing,

e) making alloys.
Galvanization:The process of forming a thick layer of zin over other metal is called  Galvanization .

Self protecting metals  : The metals that react with air to form a thin layer of their oxide over them to protect from further corrosion of oxidation are called self protecting metals. E.g. aluminium, zinc, magnesium, lead, etc.
Anodizing : The process of forming a thick layer of aluminium oxide over aluminium metal is called anodizing.
During anodizing process : A clean aluminum article is made anode and is electrolyzed with dil H2 SO4  . The oxygen gas produced at anode reacts with aluminium to make a thicker protective layer of its oxide.

CBSE Chemistry X- Ch: Metal and non Metal:Important guess very short type Questions answer solved

1 marks questions (very short answer type question)

Q.1:- Name a metal which can be cut with a knife?

Ans:- sodium

Q.2:- hich metal is the best conductor of electricity?

Ans:- silver

Q.3 Which metal is poorest conductor of electricity?

Ans:- iron

Q.4 Which metal is most ductile?

Ans.:- gold

Q.5 Which metal is best conductor of heat ?

ans:- silver(and copper)

Q.6:- Which metal other than mercury is liquid at room temperature?

Ans:- Gallium

Q.7:- Which metal is poorest conductor of heat?

Ans:- lead (and mercury)

Q.8:- What is the nature of oxides of metal?

Ans:- Basic

Q.9:- What is the nature of oxides of non- metal?

Ans:-Acidic

Q10:-Which non-metal conduct electricity?

Ans:-Graphite, allotrope of carbon conduct electricity.

Q.11:- Which non-metal is lusturous?

Ans:- iodine

Q.12:- Why metals are hard and have high melting point?

Ans:- because of their crystalline structure metals are hard.

Q.13:- What is an amalgam? Ans:- An alloy of two metals in which one is mercury is called amalgam.

Q.14:- What are the constituents of solder?

Ans:- tin and lead

Q.15:- Name the green coloured compound which appears on the surface of copper utensils?

Ans:- Basic copper carbonate

Q.16:- Why the item made of silver turns black when exposed to air?

Ans:- due to formation of silver sulphide

Q.17:- What are amphoteric oxides? Give an example.

Ans:- Oxides which react with both acids as well as bases to produce salt and water are called amphoteric oxides .for example:- Al2O3 . ZnO

Q.18:- Why sodium is kept immersed in kerosene oil?

Ans:- because sodium react with air to form Na2O (sodium oxide).

Q.19:- Which gas is produced when dil. HCl is added to a reactive metal? Write the chemical reaction when iron reacts with dil. H2SO4?

Ans:- hydrogen gas is produce when dil. HCl is added to a reactive metal.

Fe(s) + H2SO4(dil.) ------> FeSO4(aq) +H2(g)

Q.20:- Why metals like potassium and sodium catch fire when treated with water?

Ans:- The reaction between sodium and water is so violent that the H2 gas released catches fire .Reaction:- 2Na(s) + 2H2O(l) ----------> 2NaOH(aq) + H2(s) + heat energy