E-Learning

Mixtures

Learning Objectives

• To be able to classify substances into elements, compounds and mixtures on basis of their property.

• To be able to recall examples of elements and compounds.

• Perform activities to separate components of a mixture.

• Explain principle involved in using a particular technique in separating a mixture

Resources required for the topic

• GPB Chemistry : https://www.gpb.org/chemistry-study-of-matter/episodes/203

Let’s Recap

MATTER

Pure substance Mixtures

Matter is anything that has mass, occupies space and can be perceived by senses .

MIXTURES

DEFINITION: If two or more substances mixed together in any proportion, do not undergo any chemical change but retain their characteristics, the resulting mass is called as mixture.

KIND OF MIXTURES

HETEROGENEOUS MIXTURES HOMOGENEOUS MIXTURES

HETEROGENEOUS MIXTURES

• A Mixture in which various constituents are not mixed uniformly are called heterogeneous mixtures.

• Examples: - 1)A mixture of sand and sulphur.

2)A handful of soil.

Salad Oil and waterSand

HOMOGENEOUS MIXTURES

• A mixture in which different constituents are mixed uniformly is called homogeneousmixtures.

• Examples: - 1)Brass is an alloy of copper and zinc and is a homogeneous mixture

2)All solutions are homogeneous mixtures.

Milk Juice

CHARACTERISTICS OF MIXTURES

1. Variable composition – Components are present in anyratio.

Eg : Mixture of sand and salt can be in 1: 2 or 5: 6 or anyother ratio.

2. Physical change - Mixture is a result of physical change.Components are not bonded to any bonds.

Eg : In air – oxygen, nitrogen and carbon dioxide do notbind with chemical bonds.

3. No specific properties – Properties of mixture are averageproperties of their constituents .

Eg : Properties of air are mid way between oxygen andnitrogen.

4. Homogeneity – Most mixtures are heterogeneous i.e. theirconstituents are not spread evenly throughout. However,some mixtures are homogeneous .

Eg : In mixture of iron and sulphur, at some places iron ismore and at some places sulphur is more.

5. Separation – Can be separated by physical means.

Eg : Iron from sulphur can be separated using magnet.

6. Energy changes – No energy is released or absorbed duringformation of mixture.

Eg : While mixing iron and sulphur no energy is absorbed orliberated.

DIFFERENCES BETWEEN A MIXTURE AND COMPOUND

Mixtures Compounds

1.NATUREWhen two or more elements or compounds ar both

are mixed together, such that they do not combine chemically, a mixture is formed.

1. NATUREWhen two or more elements unite chemically, a compound is formed.

2.STRUCTUREMixtures are generally heterogenous, e.g., mixture

of sand and salt or iron and sulphur.However, some mixtures can be homogeneous.

2. STRUCTURECompounds are always homogeneous.

3.COMPOSITIONIn case of a mixtures their constituents can be

present in any ratio, i.e., mixtures have variable composition.

3. COMPOSITIONIn case of compounds, the constituents are present in a fixed ratio by weight.

MIXTURES COMPOUNDS

4.PROPERTIESThe constituents of a mixture retain their individual

chemical and physical properties.

4. PROPERTIESProperties of a compound are entirely different from the properties of its constituents.

5.SEPARATION OF CONSTITUENTSThe constituents of a mixture can be separated by

applying physical methods like solubility, filtration, evaporation, distillation, use of magnet

5. SEPARATION OF CONSTITUENTSThe constituents of a compound cannot be separated by applying physical methods. However, constituents of a compound can be separated by chemical means.

6.ENERGY CHANGESDuring formation of mixture no energy changes takes

place.

6. ENERGY CHANGESDuring the formation of a compound either the energy is absorbed or given out.

https://youtu.be/t0iHbY9sjDc

https://youtu.be/EXJgFyPnp1Y

Kinds of mixtures and their separation

A mixture can be solid, liquid or gases state. Also mixture can be homogeneous or heterogeneous.

Classification of mixture is as follows:

Principles involved in separation of components of mixtures

The methods necessary to separate the components of a mixture depends upon :

1. The physical state of constituents of the mixture.

2. The difference in one or more physical

properties of the constituents of the

mixture.

Following physical properties are considered in the separation of constituents of a mixture :

a) Density of constituents

b) Melting and boiling point of constituents of mixture.

c) Property of volatility of one or more constituents of mixture.

d) Solubility of constituents of mixture in various solvents.

e) Ability of constituents of mixture to sublime.

f) Magnetic properties of constituents of mixture.

g) Ability of constituents of mixture to diffuse.

Separation of common salt(NaCl) and marble powder(CaCO3)• Components of mixture: Common Salt and Marble powder

• Property of components:

✔Common salt - Soluble in water

✔Marble powder - Insoluble in water

• Process:

Dissolve mixture in good amount of water such that soluble component saltcompletely dissolves in water. Filter the solution formed . The insolublecomponent - marble powder, is left on filter paper. The soluble content commonsalt is collected as filtrate.

• Recovery of components:

✔Insoluble component - marble powder is left on filter paper. Dry it in hot air.

✔The filtrate is heated on slow heat. Solvent evaporates leaving behind commonsalt.

Separation of ammonium chloride and common salt using sublimation method• Components of mixture: Ammonium chloride and Common salt.

• Property of components:

✔Ammonium chloride - Sublimes easily

✔Common salt - Does not sublime.

• Process: The mixture is placed in china dish and heated on low flame. Aninverted dry funnel is placed over china dish and its stem is closed usingcotton wool.

• Recovery of components:

✔Ammonium chloride sublimes and its vapours condense on sides of funnelto form fine powder.

✔The residue left behind is non-sublimable component common salt.

Separation by Sedimentation and decantation• Sedimentation - The process in which

a suspension of insoluble fineparticles suspended in a liquid areallowed to stand undisturbed, suchthat solid particles settle down,leaving behind clear liquid above.

• Sediment - The insoluble solidmaterial which settles down when asuspension is allowed to standundisturbed.

• Supernatant Liquid - The clear liquidabove the sediment, when asuspension is allowed to standundisturbed.

Supernatant

liquid

Sediment

• Decantation - The process ofpouring out the clearsupernatant liquid above thesediment, thus helping theseparation of solid particles fromthe liquid is called decantation.

• This method is helpful inseparation of clay and sandparticles from muddy water.

Separation by filtration - Method for solid-liquid mixtures.• Filtration: The process of separation of

insoluble solid constituent of a mixture fromits liquid constituent, by passing it throughsome porous material is called filtration.

• Filtrate: The clear liquid obtained from amixture of a solid and a liquid by process offiltration.

• Residue: The insoluble solid constituent lefton filter paper when a mixture of aninsoluble solid and liquid is filtered.

• A glass funnel is moistened with

water.

• Filter paper cone is placed in the

glass funnel.

• Funnel is clamped on an iron stand

and under its stem is placed a

beaker.

• The suspension of solid-liquid is

poured in funnel slowly with help of

glass rod.

• The filtrate collects in beaker .

• Residue is left on filter paper.

Process of Filtration

Advantages of filtration over sedimentation and decantation

1. It is quicker process than sedimentation and decantation.

2. The insoluble solid is completely removed, which is not possible in case of decantation.

Separation by Evaporation - Method for non-volatile solid from liquid

• The process of changing a liquid into a gaseous state, below its boiling point by supply of external heat is called evaporation.

Method:

1.Heat sand in an iron vessel by placing it over tripod stand . This arrangement is called as sand bath.

2.Take clear solution of soluble non-volatile substance in china dish. Place china dish on sand bath.

3.Heat gently such that liquid evaporates, but does not boil. Continue heating till liquid completely evaporates.

• When almost dry solid is left, reduce flame and heat for another five minutes. This helps in forming:

i) Completely dry solid

ii) Will prevent spurting of solid from china dish due to excessive heat.

Separation of kerosene oil and water by using separating funnel (Liquid-Liquid mixture)

• The liquid-liquid mixture of immiscible components is poured into the funnel and allowed to stand. The liquids separate out due to difference in their densities.

Method:

1.Tap of separating funnel is closed and is clamped on iron stand.

2.The mixture is poured into the funnel and is allowed to stand for few hours.

3.The two liquids separate out into two distinct layers.

4.A conical flask is placed below the funnel and tap is opened gently such that heavy liquid trickles out in flask drop by drop.

5.Once heavier liquid is completely drained out, tap is closed.

• Water being heavier is collected in flask below.

• Kerosene is left out in separating funnel which can be collected in different flask.

Check for Understanding

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Check for Understanding

Q) State one method to separate the following mixtures :

1. Two solid mixtures, one of which directly changes into vapour on heating.

2. Solid-liquid mixture containing- an insoluble solid in liquid component.

3. A solid- liquid mixture containing a soluble solid in liquid.

4. A liquid – liquid mixture containing two immiscible liquids having different densities.

Assessment

1. Define mixture.

2. State characteristics of mixture.

3. Describe method of separation of constituents of mixture of CaCO3

and NaCl.

4. Describe method of separation of constituents of mixture of kerosene oil and water.

Assignment

1. How can you separate common salt from sea water?

2. Define sublimation. State kind of mixture in which this method is used.

3. Mention principle involved in separating oil and water.

4. Define sedimentation and decantation. Draw suitable diagrams for the same.

5. State difference between mixture and compound.

Thankyou ☺