SCIENCE PRACTICALS

class 9 science practicals

CLASS 9
Separating the components of a mixture 

The components of a heterogeneous mixture can be separated by simple methods like hand picking, sieving, filtration etc.

   Sometimes special techniques are used to separate the components of mixtures like :-

   i) Evaporation

  ii) Centrifugation

 iii) Decantation (Using separating funnel) 

 iv) Sublimation

  v) Centrifugation

 vi) Chromatography

vii) Distillation and fractional distillation

centrifugation

The method of separating denser particles and lighter particles from a mixture by using a centrifuging machine

is called centrifugation.

    Eg :- If we take some milk in a centrifuging machine and spin it rapidly, the cream separates from the milk because cream is less dense than milk.

 DECANTATION USING SEPARATING FUNNEL

This method is used for separating a mixture of immiscible liquids. Liquids separate into different layers depending on their densities.

     Eg :- If we take a mixture of kerosene oil and water in a separating funnel, it forms separate layers of oil and water. The water can be separated by opening the stop cock. After the water flows out the stop clock can be closed.

SUBLIMATION

This method is used to separate a mixture of a sublimable component from a  component  that does not sublimateby heating the mixture.

    Eg :- If a mixture of ammonium chloride and common salt is heated, the ammonium chloride sublimes and can be cooled and solidified and collected and salt is left behind

CHROMATOGRAPHY

This method is used for separating coloured components from a liquid by using a filter paper or blotting paper.

   Eg :- Put a drop of ink near one end of a strip of filter paper and dip the end of the paper in a test tube containing water. Ink is a mixture of two or more coloured components. The component which is more soluble in water rises faster and get separated.

DISTILLATION

 This method is used for separating a mixture of miscible liquids by boiling the mixture and cooling and condensing the vapours.

     Simple distillation :- is used for separating a mixture of two miscible liquids having sufficient difference in their boiling points.

     Eg :- If a mixture of acetone and water is heated in a distillation apparatus, the acetone which has a lower boiling point than water first boils and cools and condenses and is separated from the water

Fractional distillation :- is used for separating a mixture of two or more miscible liquids whose difference in boiling points is less than 25K.

    The apparatus used for fractional distillation is similar to that used for simple distillation except that a fractionating column is fitted between the distillation flask and condenser. The fractionating column has glass beads which increases the surface for the vapours to cool and condense.

    Fractional distillation is used for separating the components of petroleum, separating the different gases from air etc.

Separation of components of air

Air is a mixture of gases. The components of air can be separated by fractional distillation.

   Air is compressed by increasing the pressure and cooled by decreasing the temperature to get liquid air. The liquid air is then allowed to warm up slowly in a fractional distillation column. Then the different components separate at different heights depending on their different boiling points.

flow chart from the book

PURIFICATION OF SOLIDS BY CRYSTALLISATION

Crystallisation is the process of obtaining a pure solid in the form of crystals from its solution.

     Eg :- By crystallisation we can obtain pure copper sulphate from its solution.

     Dissolve about 5g of copper sulphate in minimum amount of water. Filter the solution to remove the impurities. Evaporate the solution in a china dish to get a saturated solution. Cover the solution with a filter paper and alllow it to cool. Pure copper sulphate crystals are formed.

TYPES OF PURE SUBSTANCES

         Pure substances are of two types. They are elements and

     compounds.

 i) Element :- is a basic form of matter which cannot be broken down

    into simpler substances by chemical reactions. Elements are of 

    three types. They are metals, non metals and  metalloids.  

   Properties of metals :-

   They have lustre. They are malleable and ductile. They are good

   conductors of heat and electricity. They are sonorous.

   Eg :- iron, aluminium, zinc, mercury, copper, silver, gold etc.

   Properties of non metals :-

   They do not have lustre. They are not malleable or ductile. They are 

   poor conductors of heat and electricity. They are not sonorus.

   Eg :- hydrogen, oxygen, nitrogen, iodine, carbon, sulphur,

   phosphorus etc.

   Properties of metalloids :-  

   Metalloids are elements which show some properties of metals and

   some properties of non metals.

   Eg :- boron, silicon, germanium etc.

(ii) COMPOUNDS

I.Multiple Choice Questions carrying one mark each –

(1)A liquid that is immiscible and two times heavier than water is mixed in it. The two liquids

can be separated by:
(a) separating funnel	(b) evaporation
(c) filtration	(d) distillation

(2)Vinegar is a mixture of acetic acid and water, it is a:

(a)homogeneous liquid in liquid mixture

(b)homogeneous liquid gas mixture

(c)hetrogeneous liquid in liquid mixture

(d)none of these

(3)Which method of separation will be used to separate iron fillings from sand?

(a) magnetic separation	(b) sieving
(c) hand picking	(d) all of these

(4)Sarita wants to separate beads of different sizes. The easiest way to separate them would be:

(a) hand picking (b) sieving (c) magnetic separation

(d) all of these

(5)A mixture contains particles of two solids of almost the same size but different weight (solid B is light, while solid A is heavy).They can be separated by:

(a) winnowing	(b) sieving
(c) filtration	(d) handpicking

2. Match the following carrying one mark each:

	(1)	Sugar		(a) mixture
	(2)	Vinegar		(b) sieving
	(3)	Mustard seeds and suji		(c) handpicking
(4) Pebbles from rice			(d) filtration
(5) Tea leaves from tea			(e) pure substance

3.Write True (T) or False (F) carrying one mark each:

(a)Soil is a mixture.

(b)Husk from grain can be separated by sieving.

(c)Decantaion can be obtained from butter milk by centrifugation.

(d)Butter can be obtained from butter milk by centrifugation.

(e)When iron fillings and sulphur powder are mixed, a homogeneous mixture is obtained.

4.Fill in the Blanks carrying one mark each:

(a)A…………… does not have a definite melting and boiling point.

(b)Stone,wood,fruits are examples of …………………. occurring materials.

(c)…………………. Is removed from sea water,to make it fit for drinking.

(d)The process of deliberately mixing food materials with cheap , unwanted things is called

………………… .

(e)The clear liquid obtained after filtration is called ………………………. .

5.Answer in one line only carrying two marks each:

(a)Define sieving.

(b)Define winnowing.

(c)Define decantation.

(d)What is mixture?

(e)What is a pure substance?

(f)Define filtration.

(g)How can pieces of iron scrap be separated from garbage dumps?

(h)What kind of mixture can be separated by handpicking?

(i)Define sedimentation.

(j)Write three properties of mixture.

(k)How are homogeneous mixtures different from heterogeneous mixtures?

(l)Write the methods you will use to separate and mixture of iron filling, common salt and Sand.

(m)Write the methods you would use to separate:

(i) Coconut oil, water &salt

(ii) Chalk powder, marbles &water

(n)Which are the two most common filters used at homes to purify water for drinking?

(o)Meenu accidently drops tea leaves into a jar containing salt. Explain the process she should use to separate them so that both could be used.

6.Answer in two or three lines only carrying three marks each:

(a)List three properties of pure substances.

(b)Write three needs for separating of constituents of a mixture.

(c)Define loading.

(d)Explain how is salt obtained from sea water.

(e)Give two reasons why components of a mixture need to be separated.

(f)Describe a simple activity to explain the process of filtration.

(g)Explain the steps how you will separate the mixture of salt, sand and water?

Chapter4: Sorting Materials into Groups

I. Multiple Choice Questions carrying one mark each:

(1) Tick the material which is man ‐made:

(a) fruits	(b) cereals
(c) glass	(d) wood
(2) Tick the material which is hard:
(a) cotton	(b) sponge
(c) metal	(d) all of these
(3) An example of soluble substance is:
(a) sand	(b) wax
(c) chalk	(d) salt

(4) A gas that comes out when you open an aerated drink bottle is:

(a) carbon dioxide (b) oxygen	(c) nitrogen	(d) hydrogen
(5) An example of a conductor is:
(a) paper	(b) wood
(c) metal	(d) rubber

2. Match the following carrying one mark each:

	(1) Combustible liquid		(a) LPG
	(2) Combustible gas		(b) camphor
(3)		Combustible solid	(c) chloroform
(4)		A volatile substance	(d) glass
(5) A brittle substance			(e) ghee

3.Write True (T) or False (F) carrying one mark each:

(a)Carbon is a malleable substance.

(b)All solids are good conductors of heat.

(c)Liquids and gases are poor conductors of heat.

(d)Early man covered his body with leaves and skin of animals.

4.Fill in the Blanks carrying one mark each:

(a)…………… helps to understand similarities and dissimilarities between objects.

(b)…………… is used to protect woollen clothes from insects and has a characteristic odour.

(c)Metals have a shiny appearance, we can say that they have a ……………………… look.

(d)………………. Is miscible in water while cooking oil is ……………………….. .

(e)We can see through air, it is ………………….

5.Answer in one line only carrying two marks each:

(a)Define malleability.

(b)Define classification.

(c)Define ductility.

(d)What is a brittleness?

(e)What is a translucent object?

(f)Define conductivity.

(h)What is a soluble substance?

(i)What is magnetic substance?

(j)How are transparent objects different from opaque objects?

(k)Which of the following is not soluble in water?

(i)Chalk (ii) common salt (iii) Sugar (iv) Milk (v) Ink.

(l)Give two examples of objects which are made of more than one material.

(m)Which of the following materials is not suitable for making a bucket:

(i) Plastic

(ii) Steel

(iii) Paper

(iv) copper

(n)Name two gases, two solids and two liquids which are soluble in water.

(o)What are translucent objects? Give examples.

6.Answer in two or three lines only carrying three marks each:

(a)Why do metal objects lose their luster after a while?

(b)Why is glass called a brittle substance?

(c)Distinguish between miscible and immiscible liquids.

(c)Write three advantages of grouping in classifying materials?

(f)Classify the following in different ways:

(i) Your clothes

(ii) Names in a phone book

(iii) Utensils in your kitchen.

(g)Give two examples to explain the same things can be made from different materials.

(h)Write seven ways in which materials can be grouped or classified.

(i)Give one similarity between wood and oxygen.

(j)Why does wax float on water while sand settles down?