CBSE Class 9 Science Preparation Of Mixture And Compound Worksheet

Physical Change
• Changes which involve a change in the physical properties of a substance.
• Formation of a new substance does not take place during a physical change.
• Most physical changes can be reversed easily
• The chemical composition of the substance undergoing a physical change remains the same.

• Chemical Change
• Changes which involve a change in the chemical composition of a substance, undergoing the change
• Formation of one or more new substances takes place during a chemical change.
• Most chemical changes can not be reversed easily.
• The chemical composition of the substance undergoing a chemical change does not remain the same
• Chemical changes are always accompanied by a change in energy

Pure substance can be classified as elements or compounds.

Element: The basic form of matter that cannot be broken down into simpler substances by chemical reactions’.

Elements can be further classified as metals, non-metals, metalloids and noble gases.

Compound: Compounds are formed when two or more elements combine chemically in a fixed proportion.

• Mixture

1. Mixtures refer to those substances which consist of two or more elements or
compounds, mixed together in any ratio and do not give rise to new compound. For
example: sea water, air, chocolate milk etc.

2. Mixture is composed of two or more substances mixed together in any ratio i.e. the
composition is variable and do not possess properties like fixed melting or boiling
point.

3. Mixture shows the properties similar to that of its constituents and they can be
separated by using physical and chemical methods.

4. There are two types of mixtures:
i. Homogeneous mixtures: Such mixtures have only one phase. They have the
same composition throughout and there is no visible separation of line between the
constituents. For example: sugar solution, vinegar etc.
ii. Heterogeneous mixture: Mixtures which has more than one phase is known as
heterogeneous mixture. There is a visible boundary of separation between the
components and they do not have the same composition throughout.

5. Homogeneous mixtures are of three types: (i) Solid homogeneous mixture (alloys),
(ii) Liquid homogeneous mixture (solution of alcohol in water) and (iii) Gaseous
homogeneous mixture (air).

6. Heterogeneous mixtures are of three types: (i) Solid heterogeneous mixture
(mixture of sand and sugar), (ii) Solid-liquid heterogeneous mixture (solution of chalk in water) and (iii) Gaseous heterogeneous mixture (smoke in air).

• Substance – Cannot be separated into its constituent particles by any physical process

• Solution – Homogeneous mixture of two or more substances

• Alloys – Homogeneous mixture of metals

• Solution:
• The component of the solution that dissolves the other component in it is called solvent (present in larger amount).
• The component of the solution that is dissolved in the solvent is called solute (present in lesser quantity).

Properties of solution:
• Homogeneous mixture
• Particles are extremely small, not visible to the naked eye
• Light path not visible
• Solute particles cannot be separated by filtration

• Suspension
• Heterogeneous mixture of solids and liquids
• Solid particles suspend throughout the medium

• Properties
• Heterogeneous mixture
• Particles visible by the naked eye
• Light path visible
• Particles settle down
• Solute particles can be separated by filtration

• Example – sand in water

• Separation process

• Evaporation – For mixture of volatile solvents and non-volatile solutes

Centrifugation – Cream from milk
• Uses
• In diagnostic laboratories for blood and urine tests
• In dairies and homes for separation of butter from milk
• For drying wet clothes

• Separating funnel – Immiscible liquids are separated out in layers (oil and water, slag in iron extraction)

Sublimation process
• Sublime solids
• Ammonium chloride
• Camphor
• Naphthalene
• Anthracene

• Chromatography – To separate those solutes that dissolve in the same solvent
• To separate
• Colours in dye
• Pigments from natural colour
• Drugs from blood

Distillation – To separate two miscible liquids that boil without decomposition (acetone + water)

Fractional distillation
• When the boiling temperature difference is less than 25 K
• (Different factions from petroleum products)
• Air components are separated by fractional distillation

Crystallization – Process to separate pure solids from a solution by forming crystal (copper sulphate from an impure sample)
• Uses – Purification of salt
• Separation of alum from an impure sample

Solvent extraction − Process to separate substances using an appropriate solvent based on the soluble nature of the components of mixture (salt + sand)

PREPARATION OF MIXTURE & COMPOUND

Experiment No: ……4……. Date: ………..

Objective: To prepare (a) mixture and (b) a compound using iron filings and sulphur powder and distinguish between these on the basis of:

(a) Appearance (homogeneity and heterogeneity); (b) Behaviour towards magnet

(c) Behaviour towards Carbon disulphide (CS2); (d) Effect of heat.

Requirements: China dish, test tubes, test tube holder, mortar and pestle, watch glasses, magnet, Bunsen burner, iron filings, tripod stand, wire gauze, sulphur powder, CS2 etc.

Procedure:

1. Take 7 g of Iron filings and 4 g of sulphur powder and mix them well using mortar and pestle. Transfer half of this into watch glass no-1

2. Take half of this mixture in a china dish heat strongly on a Bunsen burner (Use tripod stand and wire gauze) till the mixture starts to show a red glow.

3. Cool the mixture, and grind into fine powder using a mortar and pestle.

4. Transfer the powder to watch glass no-2.

5. Perform the following experiments with the samples you have in both the watch glasses.

Properties of mixture of iron &sulphur

Properties of compound of iron &sulphur

Precautions:
1. Heating of the Fe & S mixture should be done with extreme care.
2. While performing the experiments, use only very little quantity of the samples.
3. Use china dish for heating the mixture.

Questions:

1. Name the compounds formed when the following chemicals react:
a) Hydrogen and Oxygen
b) Mg and S
b) S and Fe
d) Fe and Cl₂.

2 Classify the following into homogeneous and heterogeneous mixtures.
a) Sand and saw dust
b) Sugar dissolved in water.
c) Milk
d) Powders of Fe and S

3 Suggest suitable physical methods to separate the following mixtures:
a. Fe and S Magnet
b. NaCl and water Evaporation/Boiling
c. Sand and water Filtration

4 Classify the following into compounds, elements and mixture:
a. Air b. CO₂ gas, c. Fe metal d. S powder f. Sugar solution e. Ethane
f. Fe + S g. NaCl h. SO₂ gas. i. H₂S gas j. Ammonia gas k. Milk

Multiple choice type questions

1 On heating a mixture of iron filings & sulphur ,it is observed that
a) Sulphur starts melting
b) iron filings start melting
c) mixture becomes red hot
d) mixture evaporates

2 When dilute sulphuric acid is added to a mixture of iron filings & sulphur owder ,it is observed that
a) A brisk reaction takes place without evolution of gas
b) A brisk reaction takes place with the evolution of a colourless gas
c) The yellow colour of sulphur disappears
d) Gas with the smell of rotten egg is evolved

3 A small amount of iron sulphide is added to 5 cc of carbon di sulphide and the test tube is shaken vigourously, it is seen that
a) Grey coloured iron particles dissolve,but not sulphur
b) Yellow coloured sulphur particles dissolve, but not iron
c) Both iron &sulphur dissolve to form a clear solution
d) None of the particles of the compound dissolves.

4 When a mixture iron &sulphur powder is reacted in a china dish ,then after some time it glows with
a) Yellowish colour
b) Bluish colour
c) Greenish colour
d) Reddish colour

5 On heating a mixture of iron filings &sulphur powder strongly,the colour of the product becomes
a) Grey b) Black c) Brown d) Yellow

6 To prepare iron sulphide ,by heating a mixture of iron filings &sulphur powder ,we should use
a)copper dish
b) china dish
c) petri dish
d) china dish

7 The reaction of iron and sulphur to form iron sulphide takes place at:
a) at high temperature
b) in the presence of a catalyst
c) at moderate temperature
d) in the presence of an acid