CLASS

VIVICBSE-i

Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India

SCIENCE

SEPARATION OF MIXTURES

SCIENCESCIENCE

CHEMISTRY CHEMISTRY CHEMISTRY CHEMISTRY

UNIT-6

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UNIT-6

SCIENCE

SEPARATION OF MIXTURES

SCIENCESCIENCE

CHEMISTRY CHEMISTRY CHEMISTRY CHEMISTRY

Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India

CBSE-i

CLASS - VI

CONTENTPREFACE

ACKNOWLEDGMENT

SYLLABUS COVERAGE 2

SCOPE DOCUMENT 3

CROSS CURRICULAR LINKS

MATRIX 4

RESOURCES 6

TEACHER NOTE (TN) 7

TEACHER STUDENT SUPPORT MATERIAL (TSSM) 17

1. INTRODUCTION 18

2. MIXTURES 19

(i) ITS TYPES

ACTIVITY No. 1 21

WORKSHEET No. 1 23

(ii) CHARACTERISTICS OF MIXTURES 24

3. NEED FOR SEPARATION OF MIXTURE 24

FORMATIVE ASSESSMENT - 1 26

4. METHODS TO SEPARATE MIXTURES

(A) SOLID - SOLID MIXTURES 27

(i) WINNOWING 27

(ii) SIEVING 28

(iii) HANDPICKING 28

ACTIVITY - 2A 30

ACTIVITY - 2B 31

v

v

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ACTIVITY - 2C 32

ACTIVITY - 2D 33

WORKSHEET - 2 34

(B) SOLID - LIQUID MIXTURES 35

(i) SEDIMENTATION AND DECANTATION 35

ACTIVITY - 3A 36

(ii) FILTERATION 37

ACTIVITY - 3B 38

(iii) EVAPORATION 39

ACTIVITY - 3C 40

(iv) CENTRIFUGATION 40

ACTIVITY - 3D 41

WORKSHEET - 3 42

FORMATIVE ASSESSMENT - 2 43

(C)LIQUID - LIQUID MIXTURES 43

ACTIVITY - 4 44

WORKSHEET - 4 45

SUMMATIVE ASSESSMENT 46

KEY NOTES 50

SUMMARY 51

RUBRIC : ASSESSMENT FOR LEARNING 52

•

•

SEPARATION OF

MIXTURES

1

2

SYLLABUS COVERAGE

Separation of MixturesS

Y

L

L

A

B

U

S

v

v

v

v

v

v

Introduction

Mixtures

Types of mixtures

Separation of solid mixtures

Separation of solid - liquid mixtures

Separation of liquid -liquid mixtures

3

SCOPE DOCUMENT

INTENDED LEARNING OUTCOMES:

At the end of this unit the students would be able to-

Understand what is a mixture and when do we need to separate different

components of mixtures.

List the various ways by which the components of a mixture can be separated.

Use appropriate vocabulary to describe these methods.

Reason out the principle behind these methods of separation. Intelligent use of

understanding must be directed to save 4Es, Energy, effort, environment and

Economy.

Identify the ways of separating;

a) solid –solid mixtures,

b) solid- liquid mixture,

c) liquid-liquid mixture.

CROSS- CURRICULAR LINKS

PHYSICS – Separation of mixtures iron (scrap) with the help of magnet.

English – Enriches vocabulary, improvement in reading skill.

ICT – Power Point Presentations and Videos, allows open exploration and supports

learners to work more independently.

4

MATRIX

Content/ Concepts Intended Learning Skills

What are mixtures?

Characteristics of a

mixture.

Different type of mixtures.

Homogenous

Heterogeneous

To familiarize the students with the

examples of mixture used in our

daily life.

Students would be able to identity

different examples of mixtures used

in daily life.

Observation &

recording

Listing

Curiosity to know

more about

Mixtures.

Need to separate

components of a mixture.

Processes;

to separate by property.

To separate a solid – solid mixture

To separate a mixture of colorful

beads of different sizes/ coins

of different denominations)

.(handpicking)

To separate a mixture of small stones

and bits of paper (winnowing)

To separate a mixture of wheat flour

and rice grains. (sieving)

To separate a magnetic component

from a mixture containing non-

magnetic components.

Manually separate mixtures made

from different components based on

colour, size and property.

think and (act),use

of

Psychomotor

skill. coordinated

handling of

apparatus

Solid- solid mixtures. different ways to separate complex Process skills.

5

Winnowing

Sieving

Hand picking

Solid-liquid

mixtures.

Sedimentation

Decantation

Filtration

Evaporation.

Centrifugation

mixtures in which components are

relatively less easy to separate

manually.

Different techniques/ processes to

separate solid liquid mixtures:

insoluble solid from the liquid by the

process of sedimentation and

decantation.

an insoluble solid from the liquid

completely in the lab. by the process

of filtration.

a soluble solid (salt) from a liquid in

the lab by the process of evaporation

a mixture of cream and milk by the

process of centrifugation (churning)

Observation &

Recording,

Accuracy

Liquid-liquid mixture Method to separate a liquid – liquid

mixture using separating funnel

e.g. a mixture of oil and water.

Accuracy in

measurement and

observation

6

Resources

NAME

VIDEOCLIPS/WEB LINK/POWERPOINT

Video clip1

PowerPoint

http://www.wiziq.com/tutorial/38393-Separation-of-Substances

Videoclip-2 http://www.youtube.com/watch?v=n3Usa6mOkhM

Separation of solid- solid mixture

ACTIVITY 2d

PowerPoint

Presentation-1

Separation of Solid – liquid mixture

Introduction to the topic- filtration

Web link

Animation

filtration through a animation created by Joseph Clark.

http://www.saskschools.ca/curr_content/science10/unita/redo

n17.html

Videoclip-3 http://www.youtube.com/watch?v=5rZ1JUMSmDk

(churning) ACTIVITY 3d

PowerPoint

Presentation-2

Separation of liquid – liquid mixture

Introduction to the topic

Videoclip-4 http://www.youtube.com/watch?v=vcwfhDhLiQU

Separation of liquid – liquid mixture

ACTIVITY 4

Web link http://www.slideshare.net/teocc/online-separation-techniques-

1662272

Concluding the chapter recap.

7

Teacher note (TN)

Separation of Mixtures

Dear Teacher you would have observed that ‘the nature of Science’ is not appearing the

this unit.Yes! this step is taken in awareness that by three exposures , the idea would

have seaped enough and is serving as a background for development of a rational

outlook. CBSE(i), in spirit, works to empower both teachers and students through

learning interaction.

In this unit there is an emphasis on hands-on-activities organized as introduction or to

develop the topics. Through this unit the learner will be able to:

Define the term ‘mixture’

Identify type of mixtures

Appreciate the need to separate mixtures

Understand various methods of separation of mixtures

Apply their knowledge to derive combination of methods of separation

Relate what they learn with their day-to-day experiences.

Have value added learning.

The definition of a conceptual understanding is far more valuable than cramming

definitions. However, definitions may be written by learners in there own words after

the concept is discussed. Mixture must not be the main focus but should be derived at a

later stage. As a teacher always keep in their mind that any lesson that starts with

definitions or points to learn will make students lose interest and hence will make it

difficult for them to comprehend the concept. It is therefore suggested that you should

not start the unit by listing on the board the types of mixtures and the types of methods

of separation and so on.

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The definition of the concept / term ‘mixture’ must be be arrived at a( later) stage

after the concept has been explored, thrashed out and assimilated with the relevant

examples elicited from the learners. This means care must be taken to warm up the

learners adequately at the start . Naturally, you would have to invest time in

planning the class interactions systematically as some of you might be doing. Still it

is suggested that as a pre task you find as many examples as possible. The advantage

of doing so is that when learners share their examples you would be ready to handle

them deftly to connect to the specific topic and benefit the whole class.

On the other hand, some of you may wonder why to waste human resource in asking

students for evidence and keeping it handy with oneself. Does it mean a ritualistic

practice with no trust in the capability of the learners! Infact, contrary to this view ,

such an exercise is primarily based on trust in the learners potential to observe and

express their experience- based examples in class. As a teacher it would be a rich,

diverse and authentic resource for you to decide, reorganize and even revise your

plan or strategy.

Based on your experience as a teacher you would appreciate that any lesson that

directly starts with definitions or points to learn will make students lose interest and

hence will make it not only a difficult process but may be doubtful to comprehend the

concept . You could start the unit by way of brain storming. This apparently

unstructured and unthreatening participation evoked from the learners would be

effective only when you have already reflected on the dimension of perspective

building through teaching – learning of this unit. Therefore, you may frame questions

to stimulate curiosity of the learners to know deeply and diversely about the topic. You

can choose to list responses of students about different type of mixtures and the

different methods to separate them.

You can demonstrate your acumen to organize information systematically. This is

modeling scientific process of learning. Performing the task professionally means

carefulness to display your skill to speak with modulation, work with accuracy and

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efficiency, write legibly and in an organized way. Modern values are possible to

exchange through observed action.

Introduce the topic in the class by simple examples such as the use of sieve to separate

used tea leaves from tea. Involving the students in the discussion on why tea leaves are

separated ,probe the class to at least arrive at an understanding that the tea leaves are

not useful and are undesirable so they have to be separated. This will ensure that the

students develop reasoning ability.

Question;

Of what use are the tea leaves?

How can we use the tea leaves to get maximum benefit from them? (TN unit 3 Food and

Nutrition importance of cooking, preparing nourishing tea)

What use can be made from brewed tea leaves?,

This could be taken as an example to make the learners understand the term ‘Filtration’.

separation is a simple term which is used broadly. Filteration is a separation of specific

substances i.e. a solid from a liquid.

Introduce few mixture types to them while obtaining the answers from them on what

are the components of each mixture e.g. in case of prepared Tea (mixture) the

components are tea leaves, sugar, milk & water. This mixture is a mixture of liquid and

solid. Next you may organize the information on priority basis i.e. tea and water. sugar,

milk, extra flavors would be the accessories to lend taste to the tea. The essential

components of hot and ice tea can be discussed. Here, You have temporarily

deconditioned that tea is served and consumed when only it is hot.

The encouraged learners should be asked to give more examples of such mixtures. This

can be done by the starter activity of students standing in a circle tossing the ball and

naming a mixture. Encouragement should be provided at any cost to nurture the self

worth of the child it the students if they

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Take care that while the lesson is being developed the students are not directed to the

teacher approved examples only. You, as a human being, would naturally appreciate

when learners quote your suggested information but as a professional your success lies

in enabling the learners rather than truncating their thinking to what you know. Your

readiness to grow in knowledge would impact healthy learning attitude. Save yourself

from prejudice of wanting students to agree with your answer unquestioningly. simply

follow the guideline of moving from known to unknown. This will help the you to

make the lesson more interesting when the students are taking the lesson forward

themselves.

You can take up each type of mixture named by the students in a sequence for further

study.

Step I You could prepare a concept web based on the related terms used

commonly and their scientific expressions as a starter. This could work as

an overview.

Step II Organize a route map based on your rapport with the learners and learners

style of learning. A heterogenuous class can be a real professional challenge

for a teacher to deal with.

One way could be to include:

Defining what is a mixture.

The type of mixtures.

Solid-Solid mixture

Solid-Liquid mixture

Solid-Gas mixture

Liquid-Liquid mixture

Liquid-Gas mixture

Gas-Gas mixture

Methods of separation of mixture

Need to separate the mixtures

Vocabulary development

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The concept of filtration can be further strengthened by using different examples of

mixtures depending on the size of the impurities (undesirable substances). The

demonstration of filtration process by using filter paper can be demonstrated.

Corollary can then is drawn by using the technique of question answers, suggest some

questions. It is essential to clarify the difference between the quantity (amount) and the

size of each particle.

To arrive at the understanding that filtration process is used to separate a solid from a

liquid. You need alertness to enable learners to derive the conclusion that filtration

process can be used when the following conditions are fulfilled, this will depend on the

size of the particles of impurities. Separation does not necessarily involve impure

particles.

You could attempt to be a resourceful facilitator so that the learners are able to derive

the conclusion about filtration as a process that will depend on the size of the particles

of the impurity. For this, variables could be changed and its effect observed. Evidence

based learning can become a source of careful observation.

For an extended learning the size of pores of the sieve or filter paper best suited for

different sized particles must be the focus. It will be quite challenging for the teacher to

explore if the students can relate their knowledge skillfully to the size of the particles

(undesirable substances) and the type of filter paper to be used to separate undesirable

substances from the mixtures.

For extended learning discuss examples of air conditioner, vehicles where filter is used

to keep away the particulate – material from blocking the gadget from working could

also be discussed as per the requirement of the class and the use of water filter for

purifying the water.

Cash occasions wherein through exchange of ideas, perspective building of the

learners is linked . You could ask the students to find out if in earlier time impurities

were found in things of daily use like water and food? In what ways did people get

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rid of it ? what did they use to minimize the impurity? How did development of

technology assist in purifying the essential food? Is technology based machine or

instrument enough to ensure a life without impurity? Has human agency any role to

play in creating an environment free from impurity? Suggest simple ways to do it

that can be practiced by us daily.

..

Discuss the concept of impurity in mixtures, its relation to the economic gain at the

expense of ethical aspect. Communicate about the thought of expenditure incurred

when health gets affected by impurities. Discuss the reason why people

indiscriminately use impurities? How to stop this attitude? Such exercises will trigger

the students to contribute more meaningfully to the class room discussion.

Planning is a prerequisite for effective outcome. For showing different types of

mixtures the teacher should plan different type for each type of activity.

The demonstration of solid–solid mixture may be done by mixing two substances such

as small rice grains in flour. This should be co-related with the method of separation

such as hand picking. Through some video clipping ‘winnowing’ as a method of

separation could be shown. It will arouse the curiosity of the students and they will

think about the kind of substances that can be removed by this method.

You could then help the students differentiate among the types of mixtures. spend

some time on these activities as this is the formative stage of conceptual unfolding. The

students should now be able to understand the different methods of separation are used

for different types of mixtures .when they start suggesting ways to separate different

specific mixtures know it as the application of the newly acquired concept mixtures,

The learners would further summarize what they studied about solid-solid mixture.

(rice & flour) and solid-liquid mixture (tea). The method of separation used for these

two types is handpicking, winnowing and filtration (use of sieve).

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Vocabulary development must go hand in hand while explaining the terms such as

solute, solvent, filtrate, impurities, un-desirable substances etc.

Encouraging and guiding the learners to do the comparison of filtration method of

separation with sedimentation and decantation could be achieved either by

demonstrating these processes or enabling the learners analytic and psychomotor skills.

You could employ different methods such as oral/group work/presentations so that

they are able to list the types of mixtures that can be separated by these. SPELL OUT the

steps to make the group activity challenging, interesting and conceptuallty enriching.

Help the students to go beyond what they have studied i.e. solid-solid and solid-liquid

mixtures. To enhance the observation skills the teacher could ask the students what

they observe after showing them a mixture of lime and water and by opening a cold

drink bottle. What happens when a cold drink bottle is opened? The gas escapes from

the liquid. She will be able to extract the answers from the students on the components

of mixtures in case of lime water and a cold drink.

To further develop their thinking skills she could elicit from the students that lime

water is liquid-liquid mixture and a cold drink is liquid-gas mixture. This will arouse

the curiosity of the students and they will be able to give more examples of these types

of mixtures.

Take the example of milk and water mixture and give the learners a chance to tell how

pure milk can be obtained from a mixture of milk and water. The teacher can extract the

answer that by evaporation method water will evaporate and pure milk will remain.

Does it have any impact on the quality of milk? If the milkman gives ½ liter of milk mixed with

water will the quantity of milk reduce after the evaporation of water from this mixture?

If their answer is yes! It reduces. Relate it to how milkman cheats himself .when he charges for

an amount, say,½ litre of milk but gives less than what is agreed upon. He mistakes to be clever

in earning more .actually he is socially doing an irresponsible act as we already studied in unit

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on food and nutrition about the importance of nutritious food for a healthy life. From a scientific

perspective he is compromising with the quality of food. You could now introduce the term

adulteration as an extended learning. Create an activity to sharpen the observation of the

students on what they eat. Is it their responsibility to take care of what they consume?

Similarly connect the same by discussing about the impurities added to the pulses, rice

etc. by the shopkeeper for their myopic understanding of profit. The students can be

given some project work on the role of students to increase awareness about these

issues.

Sometimes these adulterations while giving financial benefit to the shopkeepers may be

hazardous to the health of a person. Such news is often published in the newspaper.

The students may be asked to collect some relevant news from newspaper and paste

these in their notebooks. Ask the students to mock talk to the shopkeeper or the vendor

who plays with health of others and share with others.

From the story of ‘Namak Andolan’ by Gandhiji, help learners apply their knowledge

on how water evaporates when heated or kept in a container under the sun. The

concept of evaporation can hence be re-enforced.

Tell them about how salt was obtained from sea and relate it with the significance of

this salt movement by Gandhiji. Inter-disciplinary approach must be kept on mind.

This will not only make the topic interesting but will also help the students understand

the significance of science in day-to-day life.

Demonstrate an activity of mixing mustard oil with water and the learner should be

asked to suggest the method of separating mustard oil from water. Try to introduce the

use of separating funnel to separate the two liquids that do not mix with each other. It

would be interesting for the students to note that mustard oil will form a layer on top of

water. Can water settle above layer of mustard oil? What will this depend upon? The

students can be given an opportunity of a brain storming session to give the logical

answers.

15

In vocabulary development, introduce the term miscible liquids and immiscible

liquids. Miscible liquids are those that mix with each other (intermix) such as lemon

juice and water and Immiscible liquids are those that do not mix with each other such

as mustard oil and water. Can miscible liquids be separated by separating funnel? Such

answers must be obtained from the students.

Health related Value education can be further strengthened by taking the example of

Air - as a mixture. Smoke from vehicles etc. causes pollution in the air and becomes bad

for health. Ask students about their awareness regarding issue of pollution certificate.

Its importance could be highlighted as a welfare regulation act for industry or vehicles.

Refrain from giving all information to the students and allow the students to put on

their thinking caps and develop the concept of mixtures and the use of appropriate

methods of separation.

Consolidate the unit by making the students apply their knowledge to tell the need to

separate the mixtures. Following points could be extracted from the students:

1. Separate undesirable substances from mixtures (e.g. pebbles from pulses).

2. Separate un-useful substance such as tea leaves from tea. Tea leaves can be used

for other purposes. Help the students’ brain storm to find the answers.

3. Separate desired substances such as precious stones from rocks.

Show some pictures or video clipping to show the process of separating cream from

milk/curd by churning. It will be interesting to relate it back to the Grandma’s time or

a village life or even present day kitchens when many people still use this method. The

term centrifugation could be used at this stage. The teacher should be able to make the

students use their knowledge skillfully to name the types of mixtures that can be

separated by centrifugation.

For an extended learning the teacher should make the students relate the formation of

two layers in case of liquid-liquid mixture on the basis of their lighter and heavier

liquids to the layers of cream which is lighter hence will float on the milk/curd.

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Mention a type of mixture that will need more than one method of separation. E.g. a

mixture of dries leaves, sand and water will require a combination of methods to

separate the components from the mixture. The process of filtration will be used to

remove dried leaves followed by sedimentation for the sand to settle down and then

decantation for water to separate from sand.

Students can be given group activity to list few mixtures like these and to write the

combination of methods to separate the components.

To enhance logical reasoning the students should be encouraged answer questions

such as:

Why one method is unsuitable for certain mixtures?

Is the sequence of using methods of separation in a combination relevant or not?

Keep in mind that her approach is from known to unknown and from simple to

complex. The teacher must ensure that the students are facilitated to apply their

knowledge from day-to-day experiences and hence experiential learning takes its own

course. While topic is developed the students’ observation skill, thinking skill,

experimental skill is enhanced.

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TEACHER STUDENT SUPPORT

MATERIAL (TSSM)

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SEPARATION OF MIXTURES

1. INTRODUCTION:

This unit deals with the study of the mixtures. Also why we need to separate the

constituents of mixtures and the various methods available to do that.

The separation of mixtures into its constituents/components is an important process

use frequently in our daily life. The constituents of any mixture can be separated on

the basis of differences in their physical and chemical properties e.g., particle size

(small, big, solubility, effect of heat (temperature) etc. there are different kind of

mixtures that we deal with at different times.

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2. Mixtures:

A mixture is a blend of two or more substances in such a way that the particles can

be separated by physical means.

The substances that make up a mixture are called its constituents/ components.

Most of the things we come across in our daily lives such as milk, sea water, soft

drinks, smoke are mixtures.

(i) TYPE OF MIXTURES:

Mixtures are of two types, homogeneous and heterogeneous.(for information

not to be tested)

• Homogeneous mixtures have the same composition throughout the sample.

They are also called solutions. Examples of homogeneous mixtures are air,

sea-water, gasoline, brass etc.

• Heterogeneous mixtures consist of two or more parts (phases), which have

different compositions. The constituents and can be seen with the naked eye

e.g., sand and salt, chalk powder in water etc.

Table 1

Some common examples of mixtures & their constituents are given below

S.No MIXTURES CONSTITUENTS

1. Milk Water, cream, proteins, carbohydrates, fats, vitamins

&minerals

2 Tap water Water, dissolved salts

3 Smoke Carbon particles and air

4 Air Oxygen, nitrogen, carbon dioxide, water vapour

5 Sea water Water , large number of salts of metals

6 Cup of tea Water, tea leaves, milk, sugar

20

http://www.usd116.org/apalla/chem/unit2/notes/images/Pure_Mixture.jpg

Table: 2

DIFFERENT KIND OF MIXTURES WITH EXAMPLES

solid –solid mixtures,

Soil is a mixture of clay &sand

solid- liquid mixture Tiny particles of clay suspended in water

solid- gas mixture,

Soot &ash in air

liquid-liquid mixture Milk is a mixture of tiny droplets of fatty

oil in water

Liquid-gas mixture,

Water vapour in the air condenses above

the cool surface of a lake or field.

When you press the knob of an aerosol

can, a mist of liquid droplets in a gas are

seen

Gas - gas mixture,

Air

21

ACTIVITY 1. (http://www.usi.edu/extserv/kidschem/lesson3.htm)

Have students stand in a circle and make them toss a ball to each other. Each time they

toss the ball they are to name a mixture. The teacher will write these on the board or on

a large sheet of paper.

Remind the students that in brainstorming, no idea or suggestion is "silly." All ideas

should be respectfully heard. Take an uncritical position, encourage wild ideas and

discourage criticism of ideas. Have them raise their hands to respond. Write their ideas

on the board.

Aim: To familiarize with the different kind of mixture using examples from our daily

life.

For eg.

S. No Student response Teacher comment

1 Ice cream Yes

2 Soft drinks Yes

3 Distilled water No

4 Soup Yes

5 Juices Yes

6 Sugar No

7 Sugar solution Yes

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The pie diagram below shows that air and sea water are mixtures where the

components are in variable proportions.

Sea Water –A mixture of salts Air – A mixture of gases

23

WORKSHEET -1

Study the components of a mixture.

The teacher displays different mixtures and will ask the students to observe and list of

the components of each mixture. (One is done for you)

Mixture Components of each mixture

Mist

Water droplets and air

Aerosol spray

24

(ii) CHARACTERISTICS OF A MIXTURE:

• The components of the mixture exhibit their own physical and chemical

properties. For e.g. in a mixture of salt and sand, the grains of sand and the

crystalline nature of salt are retained. Also salt will show solubility in water

unlike sand.

• The components of a mixture can be easily separated using physical means

like filtration, evaporation etc

• There is no evolution or absorption of energy during the formation of a

mixture.

• A mixture has no definite physical properties like boiling point & melting

point. These change with the change in amount of constituents of the mixture.

3. NEED FOR SEPARATION OF COMPONENTS:

No substance in nature is pure. All substances contain some undesirable substances

in them which have to be removed before human consumption. The removal of

these components is called as separation of mixtures.

25

Table 3

S.NO Reason Examples

1

To remove undesirable components.

Small stones present in rice

&pulses, fine suspended

sand &clay present in pure

water.

2 To remove non useful components. Tea leaves from tea, lemon

seeds from neembu

(lemon) pani, removing the

banana peel.

3 To separate two or more different

components.

Churning of milk to obtain

butter, separating oil from

water, components of air,

green apples from red apples.

4 To obtain desirable components.

Obtaining precious gems

from rocks, obtaining rice

from a mixture of rice &husk

26

FORMATIVE ASSESSMENT -1

FILL UPS: (refer the fig. given before)

Q1) a) Air and sea water are --------------------------.

b) The two main gases in air are _____________and ________________.

c) Sea water is a mixture of water , ________________ of metals.

Q2) Looking at the pictures below answer the following questions:

1) (Fig2.a)A solution of sugar and water is a mixture. Give two reasons to support

your answer.

2) (Fig2.b) How can you separate the components of this mixture?

3) (Fig2.c) Which property is used to separate a mixture of sulphur and iron

fillings.

Fig2.a) A solution of sugar in water

Fig2.b) Fig 2.c)

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Q3) Give two reasons to support that

a) air is a mixture of gases. b) sugar solution is a mixture.

4. SEPARATION OF COMPONENTS OF A MIXTURE: METHODS

The separation of the various constituents of different mixtures depends on the

properties of the constituents. Some of these properties are size, density, magnetic

nature of particles, solubility, miscibility, differences in boiling and melting points.

A. Separation the Components of a (solid-solid) Mixture

(i) Winnowing

It is that process by which we can separate any heavy material from a lighter one

with the use of wind. It is a relevant method of separation in case of solid-solid

mixtures having components of different weights. For e.g. the wheat grains from

the field still have dried husk and chaff, which have to be separated and thrown

away before the wheat can be used. The husk is blown away as it is much lighter

than the grain. So, when the grains are gently dropped to the ground, only the

wheat grains collect there, while the husk blows away.

Mona,

There are ways to separate Mixtures…

Lets do them One by One…

Evaporation

Filtration

Hand Picking

Sieving

Decantation

Winnowing

28

Winnowing fan

(ii) Sieving is a method of separating substances that are of different sizes .The

component, having a smaller size than the holes of the sieve, passes through while

the other components remain on the sieve. For example, wheat flour has some fine

powdered wheat as well as some bigger impurities. When it is put on a sieve, the

fine powder falls through the small holes in the sieve, while the large size particles

remain as they are too big to pass through these holes. The substances are thus

separated.

sieve

(iii) Hand picking

Handpicking is the basic method for separating components of different texture,

appearance and sizes.

29

It involves simply picking out substances by hand and separating them from

others. The substances being separated may be impurities that have to be thrown

away.

It could also be that both the substances being separated are useful – such as

separating green grapes from black ones

Demonstration of the methods of hand picking, winnowing and sieving through

simple activities.

30

31

Activity - 2a

Aim: To separate a mixture of colorful beads of different sizes/ coins of different

denominations).

Learning Outcomes: Student will be able to analyze the different processes of

separating solid-solid mixtures.

Student will be able to understand when & where the process of handpicking

winnowing and sieving will be used.

Material required: coins of different denominations

Method: The students will be provided with different samples and asked to separate

them.

Record your observation: ---------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------

32

Activity - 2b

Aim : To separate a mixture of small stones and bits of paper.

Material Required: Small stones and bits of paper.

Method: The students will be provided with mixture, and asked to separate them.

They can use a fan if there is no breeze.

Bits of paper small stones

Record your observation: -------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------

33

Activity - 2c

Aim : To separate a mixture of wheat flour and rice grains.

Material required: Mixture of wheat flour and rice grains, sieve.

Method: Write the steps you would follow to do the above activity

--------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------

Record your observation: ---------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------

34

Activity - 2d

Aim: To separate a magnetic component from a mixture containing non-magnetic

components.( for eg iron and sulphur).

Principle: The magnetic component of the mixture is separated with the help of the

magnetic attraction.

Materials required: mixture of sulphur and iron, magnet

Method: A magnet is moved over the mixture containing the iron filings.

Record your observation: -------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------------------

35

WORKSHEET - 2

To separate components based on their properties.

Teacher displays different mixtures (solid mixtures) .

Study the mixtures given and suggest the type of separation method. Also support

your method by filling the property you would use to separate each component.

Students get handouts to fill after their observation.

MIXTURES PROPERTY USED TO

SEPARATE

METHOD OF

SEPARATION

36

B. Separating the Components of a Mixture (solid- liquid)

(i) Sedimentation and Decantation

Sedimentation is the process by which insoluble heavy particles in a liquid

are allowed to settle down. This is a simple process that most people use at

home. For example, settling of mud particles in water, tea leaves in hot water.

Decantation is the process by which, a clear liquid obtained after

sedimentation, is transferred into another container, without disturbing the

settled particles.

Separation of the coarse particles of a solid from a liquid by sedimentation and

decantation

37

Activity-3a

Aim : To separate the mixture of particles of a solid from a liquid e.g., muddy river

water .

Learning outcome: To observe different methods of separating solid-liquid mixture.

Teacher demonstrates the process of sedimentation and decantation.

Materials required: mixture of sand and water, a beaker.

Principle: The particles of the solid being heavier than the liquid (usually water), settle

down. The clear upper layer of the liquid is then gently poured out into another

container. Settling down of the solid particles due to the effect of gravity is called

sedimentation. The transfer of the clear upper liquid without disturbing the settled

solid particles is called decantation.

Decantation: allowing the top liquid to flow (figure 1)

Method: we take a mixture of sand and water in a beaker and let it stand for sometime.

Record your observation: -------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------

38

(ii) Filtration:

Mixtures can often be separated by filtration. The mixture is poured over a piece

of paper that only allows molecules below a certain size to pass through it. The

larger components of the mixture will be trapped on the paper. For example a

mixture of sand and water can be separated as shown in the fig below.

Fig 2: Demonstrating various stages of filtration

Observe the stages a) to c) carefully. What fo you think would have happened ?

What could have happened had we used an ordinary paper in the funnel ? where else

did you not the use of a filter paper in everyday life ? the solid remains on the filter

paper and is called a residue. While the liquid that gets collected in the beaker below

is called filterate.

Can we say a filteration process helps to separate a filtrate from the residue ?

Residue: The solid that remains on the filter paper

Filtrate: The liquid that is collected

Filtration is not limited to solid-liquid separations such as sand and water. There is also

a filtration system present in air-conditioners, where dust and dirt particles are

cleansed from the air by the air filter.

39

Activity-3b

Aim : To separate the insoluble solid component of a mixture from the liquid

completely.

Learning outcome: Student will be able to understand the process of filtration.

Materials required: mixture of sand and water, beaker, filter paper, funnel.

Principle: The solvent molecules present in the solution can pass through the porous

membranes while the suspended particles cannot and are retained on the porous filter

paper.

Method: we take a mixture of sand and water in a beaker and clamp the funnel to a

stand and insert a filter paper in the funnel .

Place a clean beaker below the funnel, and pour the mixture in small quantities into the

funnel using a glass rod.

Record your observation: -------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------

40

(iii) Evaporation

Separating homogeneous mixtures can be more difficult. The common way to separate

these mixtures is by Evaporation

This method is useful for separating a soluble solid from a liquid (a soluble substance

dissolves in water to form a solution).

For example: separating salt from sea water, copper sulphate crystals can be separated

from copper sulphate solution using evaporation.

NOTE: It is the water that evaporates , not the solution.

41

Activity - 3c

Aim : To separate a soluble solid (salt) from a liquid.

Learning outcome: Student will be able to understand the process of evaporation

Material required: mixture of salt and water, porcelain dish, beaker, Bunsen burner.

Principle: Liquids evaporate at all temperatures. Evaporation becomes faster at higher

temperatures

Method: we take a mixture of salt and water in a beaker and heat it on a Bunsen burner.

Record your observation: ---------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------

(iv) CENTRIFUGATION

The process of separating lighter component from a heavier component in a

mixture by churning is called (centrifugation) .demonstration of the process of

centrifugation can be followed by discussion.

42

Activity - 3d

Aim : To separate a mixture of cream and milk.

Learning outcome: Student will be able to understand the process of centrifugation

(churning)

Material required: full cream milk, churner, blender ? mixie ?

Method: Take a mixture of full cream milk and put it in a churner. Switch on the

machine and allow it to work for few minutes. What do you observe.

Record your observation: ---------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------

Practice Question: Devesh has a mixture of salt, sand and stones. He needs to separate

these components from the mixture.

Write the order 0f steps he could take to separate the mixture. Also mention the

components separated in each step.

43

WORKSHEET- 3

Separation of solid-liquid mixtures.

1. Identify the method of separation in each of the pictures given below.

i)

---------------------------------------------

ii)

---------------------------------------------

iii)

---------------------------------------------

iv)

---------------------------------------------

44

FORMATIVE ASSESSMENT: 2

FILL UPS:

1. Pebbles can be separated from grains by-----------------.

2. Cream can be separated from milk by----------------------.

3. The removal of husk from grain is called------------------.

4. The process of settling down of insoluble particles in a suspension is called ---------.

5. Common salt is obtained from sea water by------------------.

6. Before cooking, rice or pulses are washed with water. This water is removed by a

process called------------------.

7. Label the fig shown above.

8. A sieve can be used to separate pulses from water:

a) How does the sieve trap the pulses?

b) what would happen if the sieves holes were bigger than the pulses ?

9. Explain with the help of a flow chart, how would you separate a mixture of salt

and pepper.

10. Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?

C. Separating the Components of a Mixture (liquid- liquid)

Liquid-liquid mixtures can be separated using a separating funnel. It is used to

separate liquids of different densities as these liquids do not intermix. They form

separate layers.

45

Activity - 4

Aim : To separate a mixture of oil and water using separating funnel.

Learning outcome: Student will be able to understand how to separate liquid mixtures

of different densities by taking a mixture of oil and water

Teacher demonstrates separation of oil from water using the process of decantation.

Materials required: mixture of oil and water, separating funnel, beaker, tripod stand.

Method: Take a mixture of oil and water. Set up the apparatus as shown in fig. below.

. –

Place a empty beaker under the funnel and allow it to stand for some time. The oil

forms a separate layer above water. Would it help to use a filter paper to separate the

above mixture ?

Record your observation: -------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------

Video clipping: http://www.youtube.com/watch?v=vcwfhDhLiQU

46

WORKSHEET – 4

Separation of Liquid Mixtures. (Oil and Water)

1. i) Identify the apparatus.

ii) What is it used for?

iii) Which liquid forms the top layer and why?

2. Mustard oil gets accidentally mixed with water. How would you remove mustard

oil from water?

3. Following are the pictures of two funnels. what are they used for?

(a) (b)

47

SUMMATIVE ASSESSMENT

Q. 1. State whether the following statements are true or false?

a) A mixture of milk and water can be separated by filtration.

b) A mixture of powdered salt and sugar can be separated by process of

winnowing.

c) Separation of sugar from tea can be done with filtration.

d) Grain and husk can be separated with the process of decantation.

Q. 2. Fill up the blanks:

a) The method of separating seeds of paddy from its stalks is called ...................

b) When milk, cooled after boiling, is poured onto a piece of cloth the cream is

left behind on it. This process of separating cream from milk is an example of

....................

c) Salt is obtained from sea water by the process of ...................

d) Impurities get settled at the bottom of a bucket when muddy water is kept

overnight in it . The clear water is then poured off from the top. The process

of separation used in this example is called ....................

Q. 3. Choose the correct option in each of the following:

i) The diagram shows the stages involved in preparing filter paper for a filtration.

Which one of the following is the correct order for the folding of the filter paper?

48

a) C D A B

b) B D A C

c) C A D B

d) A B C D

ii) The diagram shows on apparatus for separating soil

and water. What are the labeled parts called ?

a) A = filtrate, B = residue

b) A = residue, B = distillate

c) A = distillate, B = filtrate

d) A = residue, B = filtrate

iii) The separation technique that involves heating a solution until the liquid

changes into a gaseous state is known as

a) vaporization

b) filtration

c) decanting

d) evaporation

iv) Name the separation technique shown in the

diagram

a) evaporation

b) sedimentation

49

c) decanting

d) filtration

5. All life in the world majorly depends on the presence of air. Is it an element, a

compound or a mixture?

A. Element

B. Compound

C. Mixture

6. An unknown, clear liquid is given to you in a beaker. You transfer the liquid from

the beaker to a clean, empty test-tube, and begin to heat it. After a while, you see

vapours (which on further analysis you discover these are vapors of water) rising

from the test-tube, and pretty soon, all that's left is are a few crystals of salt stuck to

the edges. Was that liquid an element, compound or a mixture? Why would you

say so ?

a) Element

b) Compound

c) Mixture

Q4. Match columns A and B

A B

a) smoke i) A gaseous mixture

b) A sugar solution ii) A gas-liquid mixture

c) Air iii) A solid-gas mixture

d) A lemon-water mixture iv) A solid-liquid mixture

e) Carbonated drink v) A liquid-liquid mixture

50

Q5. Complete the table with appropriate terms:

Type of mixture Example Method of Separation

A solid-liquid mixture Filtration

Sand and water

A liquid-liquid mixture

Tea leaves and tea

Q6. Which of the following are mixtures.

a). Chicken noodle soup

b). Salad.

c). Table salt

d). Orange juice.

Q7. How does the process of filtration work? Is it better than decantation give reasons

to support your answer?

Q8. Why does sky become clear after rains?

Q9. How will you separate the following mixtures? Explain your answer giving

specific reason for the choice of your answer

a) Rice and dal,

b) Mud and gravels,

c) Hay and soil,

d) iron nails, salt and sand

clue: step 1: magnetic separation

step 2 : add water . Filtration

Step 3 : evaporate the filtrate

51

KEY NOTES

Mixture contains two (or more) substances that are not

chemically joined together

e.g. Air, sea water,

chicken soup

Residue The solid left behind after an experiment (e.g. the

solid left in the filter paper). Sand

Soluble: Can dissolve

Sugar in water

Insoluble:

Cannot dissolve

Sand in water

Solvent The liquid that is used to make a solution

Water, alcohol

Solute A substance that has been dissolved in a solution. Sugar, Salt

Density Is defined as mass per unit volume. /or how heavy

or light a substance is.

52

Summary of Some Methods used to Separate Mixtures

PROCESS What it is used for Examples

Filtration Used for separating a solid from a liquid E.g. separating sand

from water.

Evaporation Used to obtain the solute from a solution e.g. for obtaining salt

from salty water

Sieving Used to separate smaller particles from bigger

ones by passing through a sieve

e.g. flour

Hand picking Used to separate solids of different colours,

shapes &size

e.g. beads, coins of

different sizes

Winnowing Used to separate lighter particles from heavier

ones.

Wheat from chaff

Sedimentation Used to separate heavier solid particles from

a liquid by the process of settling down.

Sand & water

Decantation Used to separate a liquid by gently pouring it

without disturbing the sediment

Sand & water

53

Rubric: Assessment for Learning

PARAMETERS Beginning (1) Approaching (2) Meeting (3) Exceeding (4)

Student is able

to plan

investigations

and set

procedure;

Procedures are

unclear or

absent

clearly

identified

clearly

Identified and

implied.

clearly

identified

and

formulated in

a manner that

can be

replicated

able to execute

investigation

and collect data

un able to

execute

investigation

and collect

data

able to execute

investigation

and collect data

has some clarity

able to execute

an investigation

and collect data

precisely.

Able to

execute an

investigation

and collect

data clearly.

able to evaluate

data and

communicate

findings in a

logical way

Scientific

information is

unclear

Scientific

information has

some clarity.

Scientific

information is

communicated

clearly

Scientific

information is

communicated

clearly and

precisely.

Student has

deep

Understanding

of the topic, can

make

connections

with concept.

Scientific

information has

major

inaccuracies or

is over

simplified

Scientific

information has

occasional

Inaccuracies or

is simplified.

Scientific

information

and ideas are

accurate.

Scientific

information

and ideas

are accurate,

thoughtfully

explained.

all images are from www.google.co.in/images

Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India

CENTRAL BOARD OF SECONDARY EDUCATION