IS MATTER AROUND US PURE?

Chemical classification of matter [NOTE: to be done in L.H.S ]

I. a) PURE SUBSTANCE: Pure substances are elements and compounds having uniform

composition of similar atoms or molecules in a fixed ratio.

Eg: ELEMENTS: Substance having similar kind of atoms. Eg: H, O, Na, Cl

COMPOUNDS: Pure substances in which two or more elements (dissimilar atoms)

combine chemically in a fixed ratio by weight. Eg: CuSO4, BaSO4, NaOH, H2O.

b) MIXTURE: Two or more substances which remain together and can be separated by

simple physical methods.

TYPES OF MIXTURES:

i) Homogeneous mixtures: Mixtures with uniform composition.

Eg: air, alloys, salt solution, lemonade, alcohol + water

ii) Heterogeneous mixtures: Mixtures with non – uniform composition.

Eg: soil+ water, oil +water, S + Fe fillings, chalk+water, smoke (mixture of

carbon particles in air)

Tabulate the differences between compounds and mixtures with examples

Compounds Mixtures

1. Compounds are formed as a result of chemical

reactions between two or more elements .

1. They are formed by simple mixing of 2 or

more constituents

2. Components of a compound are always

present in a definite ratio by mass

2.The components of a mixture may be present

in any ratio.

2. Homogeneous in nature 3. Can be homogeneous or heterogeneous.

4. Properties of a compound are entirely different

from its constituents.

4. Properties of a mixture are same as those of

its constituents.

5. Components of compound can be separated by

Chemical methods.

5. Components of a mixture can be

separated by physical methods.

6.Melting and boiling points of a compound are

fixed

6. Melting and boiling points of a mixture are

usually not fixed.

Tabulate the differences between Elements and Compounds with examples

Element Compound

1.Consists of same kind of atoms. 1.Dissimilar atoms combine in a fixed ratio.

2.Elements cannot be broken down. 2.Compounds can be broken by chemical methods

3.H,Na,Li,Pb…. 3.CO2,SiO2,H2SO4….

Q1. Air is considered to be mixture. Justify i) Air is a homogeneous mixture of different gases (N2 , O2 , CO2 , watervapour

, noble gases)

ii) The component gases retain their individual properties

iii) The components of air can be separated by physical methods (liquefaction

followed by fractional distillation)

Home work: Q The mixture of sulphur and iron filling is considered to be heterogeneous

in nature. Give reasons.

Q2. CO2 is a compound. Prove it.

i) CO2 has C and O in the ratio of 1:2

ii) C and O lose their individual properties after forming CO2.

iii) The components cannot be separated by physical methods.

iv) A compound has fixed melting and boiling point.

Homework: Solve worksheet

II. SOLUTIONS:

➢ It is a homogeneous mixture of two or more substances (also called as true solution)

➢ It has two components solute and the solvent.

Solute +solvent = solution

Eg: i) sugar + water = sugar solution

iii) Iodine + alcohol = Tincture of iodine

➢ Solute: substance which dissolves in solvent to form solution (present in less

amount)

➢ Solvent: substance in which solute dissolves to form solution (present in larger

amount)

Eg: water of sugar solution

TYPES OF SOLUTIONS:

1. Saturated solution: A solution in which no more solute can be added to form a

true solution.

Amount of solute = solubility

Eg: 36gms of NaCl dissolves completely in 100gm of water at 20OC

Note: Solubility depends on temperature.

➢ Solubility of solid in liquid increases with increase in temperature.’

➢ Solubility of a gas in liquid decreases with increase in temperature.

2. Unsaturated solution: A solution in which more solute can be added to make it

saturated.

Amount of solute < solubility

Eg: 20gm of NaCl is dissolved in 100ml of water at 20OC.

3. Super saturated solution: A solution in which some solute is left undissolved.

Amount of solute > solubility

Eg: 50gms of NaCl is present in 100ml of water at 20OC.

Tabulate the difference between [NOTE: to be done in L.H.S]

a) Homogeneous mixture and Heterogeneous mixtures with examples

b) Saturated and Unsaturated solutions with

examples CONCENTRATION OF SOLUTION:

➢ The amount of solute present in a solution.

➢ Concentration can be expressed in m/m %, v/v %, m/v%

➢ Concentration of solution = 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑆𝑜𝑙𝑢𝑡𝑖𝑜𝑛

➢ Solute + solvent = solution

% concentration = 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 solute X 100

𝑋 100

𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 + 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑣𝑒𝑛𝑡

NUMERICAL PROBLEMS:

1. 10gm of CuSO4 is added to 90ml water to make a saturated solution. Find the %

concentration of the solution.

Solution:

Given CuSO 4 (solute) = 10gm

Water (solvent)= 90ml [or 90gm]

% concentration =?

% concentration = 𝑎𝑚𝑜𝑢𝑛𝑡𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 + 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑣𝑒𝑛𝑡

𝑋 100.

% concentration = 10

10 + 90 𝑋 100 = 10 %.

2. 30% of HNO3 is prepared by adding nitric acid to 200ml distilled water. Find the

amount of acid used?

Solution:

Given % concentration = 30%

Water (solvent) = 200ml

Acid (solute) = x ml

% concentration = 𝑎𝑚𝑜𝑢𝑛𝑡𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 + 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑣𝑒𝑛𝑡

𝑋 100.

30 % = 𝑥 𝑥+200

𝑋 100

30 (x+200) = 100x

6000 = 100x -30x

x = 6000 / 70 = 85.7ml

3. How will you prepare 10% of 500ml sugar solution?

Solution:

Given % concentration = 10%

Solution = 500ml

Solute = x gm

Concentration of solution = 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑆𝑜𝑙𝑢𝑡𝑖𝑜𝑛

𝑋 100

10 = x/ 500 X 100

(Sugar) x = 50gm

Solvent (water) = solution - solute

= 500- 50

= 450 ml.

Homework questions:

Q1. 32ml of kerosene is added to petrol to prepare 20% of its solution. Find the amount of

petrol required?

(Hint kerosene (solute) petrol (solvent)

Q2. Solve Pg 17 eg2.1

Home work: solve worksheet questions of above sums of concentration.

Properties of True Solutions:

➢ Homogeneous mixture

➢ Solute particle size less than 1nm [ 1 nm = 10 -9

m]

➢ Solute particles are very small in size and cannot be separated by filtration but can be separated

by evaporation.

➢ They are stable. Solute particles do not separate on leaving undisturbed.

➢ Does not show tyndall effect

➢ Examples: Sugar solution, CuSO4 solution

TYNDALL EFFECT: The phenomenon of scattering of light rays by the particles in the medium so

that the path of the light rays can be seen.

Eg: 1. Sunlight passing through canopy of a dense forest gets scattered.

2. Light seen from the projector

3. Light from the car head light during night times.

SUSPENSIONS:

➢ Heterogeneous mixture

➢ Solute particle size is greater than 100nm.

➢ Solute particles can be seen with the eyes.

➢ Suspensions are unstable, solute particles settle down when left undisturbed.

➢ They show tyndall effect in the disturbed state, but does not show tyndall effect When the

particles settle down.

➢ Solute particles are separated by simple physical methods like filtration.

➢ Examples: sulphur + iron filling

Sand + water, chalk powder + water

COLLOIDS:

➢ Heterogeneous mixture in which solute particle size is in between 1 nm and 100nm.

➢ Brownian movement: particles of colloid move in zig - zag motion giving it a blurred

appearance. This movement is called Brownian movement.

➢ A colloid has two component

i) Dispersed phase (component in less quantity - solute)

ii) Dispersion medium (component in larger quantity - solvent)

➢ Solute particles do not settle down when left undisturbed.

➢ Particles cannot be separated by ordinary filter paper, but can be separated by special techniques

- Ultra filtration, centrifugation

➢ Colloids show tyndall effect

➢ Examples starch solution, egg albumin + water, blood, milk etc.

Home work: solve blue box questions pg no 18

TYPES OF COLLOIDS:

Depending on the physical state of the dispersed phase and dispersing medium colloids are classified

into 8 types:

1. Sol: A colloid of solid dispersed phase in liquid / solid dispersing medium. Eg: starch solution, mud

water, milk of magnesia etc.

2. Emulsion: A colloid of liquid dispersed phase in liquid dispersing medium.

Eg : milk, face cream

3. Aerosol: A colloid of solid / liquid dispersed phase in gas dispersing medium. Eg fog, clouds,

smoke, automobile exhaust.

4. Foam: A colloid of gas dispersed phase in solid / liquid dispersing medium. Eg: rubber, sponge ,

shaving cream

5. Gel: A colloid of liquid dispersed phase in solid dispersing medium. Eg: jelly, cheese, butter

Home work: Draw table 2.1 and write common examples of colloids.

SEPERATION OF MIXTURES:

Principle: the components of a mixture can be separated based on the difference in the physical and

chemical properties between the different components of the mixture.

I. Separation of coloured component (Dye) from ink: - Evaporation

Principle: Evaporation technique is applied non - volatile (dye) from volatile water (ink)

Procedure:

➢ Take a beaker half filled with water.

➢ Place watch glass on the mouth of the beaker and put few drops of ink.

➢ Place the beaker on a tripod stand with a wire gauze.

➢ Start heating the beaker. Steam formed in the beaker will heat the watch glass.

➢ Water evaporates from ink leaving behind the dye in the watch glass.

Application:

➢ To obtain salt from sea water.

[Home work: Draw fig.2.5 pg.19 in L.H.S]

II. Separation of cream from milk. (Centrifugation)

Principle: to separate denser particles from lighter particles in a medium.

Procedure:

➢ Take some full cream milk in a test tube and place in a centrifuge machine.

➢ Run the centrifuge machine for about 2 minutes.

➢ The lighter cream particles of milk move to the surface and the denser part of the milk remains in

the bottom.

Application:

1. To separate cream from milk

2. To test urine and blood samples in diagnostics laboratories.

3. Used in washing machines to dirt and also squeeze water from wet clothes.

III. Separation of immiscible liquids:

Immiscible Liquids: Liquids that do not dissolve in each other. Eg: oil and water, petrol + water

Principle: Separating funnel is used to separate immiscible liquids based on their difference in

densities.

Procedure:

➢ Take a mixture of kerosene and water each 50ml in a separating funnel and allow it to stand

undisturbed for some time.

➢ We observe that lighter kerosene floats on heavier water

➢ If we open the stopcock, water drips out of the funnel slowly. Close the stopcock as the kerosene

Applications:

1. To separate a mixture of oil and water

2. To separate lighter slag from the heavier molten iron during the extraction of iron from its ore.

Home work: draw fig 2.6 from pg 20.

IV. To separate a mixture of sodium chloride and ammonium chloride [SUBLIMATION]

Principle: sublimation technique is used to separate a mixture of sublimable and non - sublimable

salts.

Procedure:

➢ Take a mixture of NaCl and NH4Cl in a china dish and place it on a tripod stand with a wire

gauze.

➢ Put an inverted funnel over the china dish and plug the stem of the funnel with cotton.

➢ Start heating the china dish slowly.

➢ We observe dense white fumes of NH4Cl emitting out.

➢ These fumes cool and condense in the inner walls of the funnel which can be scrapped out and

NaCl remains in the china dish.

Uses: to separate sublimable and non - sublimable salts.

Note: Draw fig 2.7 from pg no 20

V. SEPARATION OF DIFFERENT COLOUR DYES FROM BLACK INK.

Principle: Chromatography technique is applied to separate different dyes (solutes) that dissolve in ink

(same solvent) based on the difference in solubility.

Procedure:

➢ Take a filter paper and cut it into a thin strip.

➢ Draw a line 3cm approximately above from one end and then put a drop of black ink in the centre

of the line and dry.

➢ Lower the filter paper in the beaker half filled with water in such a way that the ink does not

touch the surface of water.

➢ Later we find that different dyes present in the ink absorb water, rises up to different heights on

the filter paper due to difference in their solubility.

Applications:

➢ Separation of colors from dyes

➢ Pigments from plant parts.

➢ To test drugs in blood.

Note: Draw fig 2.8 from pg no 21 in L.H.S

VI. Separation of miscible liquids:

Note: Liquids which dissolve or mix in each other are called miscible liquids. Eg alcohol and water,

Acetone and water.

A) SIMPLE DISTILLATION:

Principle: separation of miscible liquids which has more difference in their boiling points (more than

25oC)

Procedure:

➢ A mixture of acetone and water is taken in a distillation flask fitted with a rubber cork.

➢ The rubber cork is fixed to a thermometer and a delivery tube which is in turn connected to a

water condenser.

➢ Steam the mixture slowly by using Bunsen burner.

➢ We observe that acetone having lower boiling point vaporizes first and condenses in the

condenser4 and is collected separately.

➢ Water having higher boiling point in the distillation flask.

➢ Thermometer records the constant boiling point of the two liquids.

USES:

➢ To separate miscible liquids having large difference in their boiling points.

[Note: Draw fig 2.9 from pg no 2 in L.H.S]

B) FRACTIONAL DISTILLATION:

Principle: Separation of two miscible liquids having less difference in their boiling points (less than

25oC )

Procedure:

➢ Take the mixture of liquids in a distillation flask fitted with a condenser, thermometer to

fractionating column.

➢ The fractionating column is filled with glass beads. These beads provide surface area for the pure

vapours to move and cool into the condenser and avoid mixing of vapors.

➢ Liquids with low boiling points starts vaporizing first and are condensed in the condenser which

are collected as pure liquids after passing through the fractionating column.

➢ Thermometer connected to the fractionating column records the boiling points of liquids

vaporizing,

➢ In this way mixture of several liquids can be separated.

Uses:

➢ Crude oil / petroleum is refined and separated into different petro chemicals by the process of

fractional distillation.

➢ Separation of gases from liquid air.

[Note: Draw fig 2.10 from pg no 22 in L.H.S]

VII. LIQUIFACTION OF AIR (separation of gases from liquid air)

Principle: Conversion of air to liquid under high pressure and low temperature followed by fractional

distillation.

Air

Filter to remove solid dust particles

Compressed and cooled by applying high pressure and low temperature

Liquid air

Fracttional distillation

O2 , Ar , N2 (seperates out first)

(-183O C) (-186OC) (-196OC)

Increasing order of boiling point

N2 < Ar < O2

VIII. Crystallisation or purification of salts.

Principle: purification of salts by filtration on followed by evaporation.

Procedure:

➢ Take 10gm of impure CuSO4, in a beaker and add water to dissolve the salt to prepare a saturated

solution.

➢ Filter the solution to remove undissolved impurities.

➢ Take a filtered solution in the china dish and boil it to make a saturated solution. Cool the

solution slowly.

➢ Pure crystals of CuSO4 are formed in the liquid at the bottom which can be obtained by the

decantation of top liquid.

Uses:

➢ To purify common salt

➢ To purify alum and sugar

IX. WATER PURIFICATION SYSTEM IN WATER WORKS:

STEP 1 : Reservoir

STEP 2 : Sedimentation tank [to remove denser particles]

STEP 3 : Loading tank [to remove suspended impurities]

STEP 4 : Filtration tank [to remove lighter impurities]

STEP 5 : Chlorination tank [to kill microbes]

STEP 6 : Supply

PHYSICAL AND CHEMICAL CHANGES:

PHYSICAL CHANGE CHEMICAL CHANGE

Reversible change Irreversible change

Change in physical properties only Change in both physical and chemical properties

No new substance is formed New substance is formed

Temporary change Permanent change

Eg: sublimation, crystallisation, liquifaction etc. Eg: corrosion of metals, digestion of food,

burning of fuels.

NOTE: Burning of candle is both physical and chemical change

PURE SUBSTANCE:

➢ Substances which contain only one kind of particles.

➢ They are classified into elements (same kind of atoms) and compounds (same kind of molecules)

➢ Elements are classified into metals, non - metals and metalloids.

PROPERTIES OF METALS:

➢ Metals are the elements which loses electrons to form cations.

➢ Metals are generally solids except mercury (liquid metal) at room temperature.

➢ Good conductors of heat.

Silver - best, lead and mercury - poor conductors

➢ Good conductors of electricity

Silver - best, mercury and iron - poor conductors

➢ They are malleable and ductile.

Gold and silver - best, zinc - brittle

➢ Lustrous and sonorous

Eg: lead, tin, nickel etc.

PROPERTIES OF NON - METALS:

➢ Non - metals are the elements that gain electrons to form anion.

➢ All are solids and gases except liquid bromine

➢ Bad conductors of heat

➢ Bad conductors of electricity except graphite

➢ Non - malleable and non - ductile

➢ Non - sonorous

➢ Generally, non - lustrous except graphite

➢ Eg: Oxygen, hydrogen, nitrogen, carbon, Sulphur, etc.

METALLOIDS:

Elements having properties of both metals and non – metals.

Eg: boron, silicon, arsenic, silicon, germanium etc.