Pure Substances, Mixtures and Separation of Mixtures
Complete Exercise I and Exercise II solutions with interactive answer cards, clear explanations, corrected chemistry facts and a quick revision lab.
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Pure substance
Only one kind of particle, a definite composition and characteristic properties. Examples: gold and distilled water.
Mixture
Two or more substances physically combined in any proportion. The components retain their individual properties.
Separation
A physical method chosen according to differences in solubility, particle size, density, magnetism or boiling point.
Tap-to-Reveal Mixture Lab
Predict each classification, then tap the card to check your answer.
Practice section
Exercise I — Objective Type Questions
Question 1(i)A mixture of mustard oil and water forms:
A mixture of mustard oil and water forms:
Correct answera heterogeneous mixture
Reason: Mustard oil and water are immiscible liquids. Their mixture is not uniformly distributed throughout. Hence, they form a heterogeneous mixture.
A compound is a chemical combination of substances. Oil and water do not chemically combine. An alloy is a mixture of metals. In a homogeneous mixture, components are uniformly mixed. Oil and water are not.
Question 1(ii)A heterogeneous mixture is:
A heterogeneous mixture is:
Correct answermade up of different kinds of atoms and molecules.
Reason: A heterogeneous mixture is made up of different kinds of atoms and molecules which do not mix uniformly.
Question 1(iii)An example of a homogeneous mixture is:
An example of a homogeneous mixture is:
Correct answertap water
Reason: Tap water is a homogeneous mixture because it contains minerals and salts which are evenly mixed, so it looks uniform throughout.
Distilled water is a pure substance, not a mixture. In sand and water, components are not uniformly mixed; sand settles down, so it is a heterogeneous mixture. Sawdust floats and does not mix uniformly, so it is a heterogeneous mixture.
Question 1(iv)Which among the following is a set containing only mixtures?
Which among the following is a set containing only mixtures?
Correct answeralloy, ink, honey, ice-cream
Reason: The set “alloy, ink, honey and ice cream” contains only mixtures because:
(i) Alloy: a mixture of metals, or of a metal and another element
(ii) Ink: a mixture of dyes or pigments and solvents
(iii) Honey: a mixture mainly containing different sugars and water
(iv) Ice cream: a mixture of milk ingredients, sugar, flavours and air.
Question 1(v)Copper is not a part of the alloy:
Copper is not a part of the alloy:
Correct answersteel
Reason: Brass, bronze and duralumin contain copper along with other elements, whereas steel mainly contains iron and carbon.
Brass is an alloy of copper and zinc, so it contains copper. Bronze is an alloy of copper and tin, so it contains copper. Duralumin is mainly aluminium with small amounts of copper, magnesium, and manganese.
Question 1(vi)Which of the following is not a mixture?
Which of the following is not a mixture?
Correct answerDistilled water
Reason: Distilled water is a pure substance, consisting of only H2O molecules without any dissolved salts, minerals, or impurities.
Question 1(vii)Which of the following is a mixture?
Which of the following is a mixture?
Correct answerHoney
Reason: Honey is a mixture mainly containing different sugars, water and small amounts of other substances.
Sugar (sucrose) is a pure compound, not a mixture. Common salt and iron sulphide are compounds.
Practice section
Exercise I — Identify
Question 2Identify the mixtures and compounds from the following list:
Identify the mixtures and compounds from the following list:
Air, water, sugar, salt, milk, tea, alcohol, honey, soil, glucose.
Correct answerMixtures — Air, milk, tea, honey, soil.
Compounds — Water, sugar, common salt, alcohol (ethanol) and glucose.
Practice section
Exercise I — Classify the Following
Question 3Select homogeneous and heterogeneous mixtures from the following:
Select homogeneous and heterogeneous mixtures from the following:
Salt solution, petrol and water, sand and charcoal, alcohol and water, air dissolved in water, air, sea water, fruit juices, mist, brass.
Homogeneous mixture:
Salt solution
Alcohol and water
Air
Air dissolved in water
Sea water
Brass
Filtered fruit juice
Heterogeneous mixture:
Petrol and water
Sand and charcoal
Mist
Practice section
Exercise I — Select the Odd One
Question 4Select the odd one out from the following:
Select the odd one out from the following:
(a) Salt solution, sugar solution, water and alcohol, sand and water
(b) Chalk and sand, water and petrol, iron and sulphur, salt and water
(c) Gold, iron sulphide, milk, water
(a) Sand and water
Reason: Sand and water is a heterogeneous mixture, while the others are homogeneous mixtures.
(b) Salt and water
Reason: Salt and water is a homogeneous mixture, others form heterogeneous mixture.
(c) Milk
Reason: Milk is a mixture, whereas, iron sulphide, gold and water are pure substances.
Practice section
Exercise I — Short Answer Type Questions
Question 1Give two examples for each of the following types of mixtures.
Give two examples for each of the following types of mixtures.
(a) solid-solid
(b) solid-liquid
(c) liquid-gas
(d) gas-gas
(a) solid-solid:
Alloys
Sand and sugar
(b) solid-liquid:
Sand in water
Salt and water
(c) liquid-gas:
Mist
Carbon dioxide and water
(d) gas-gas:
Air
Helium and oxygen
Question 2Name the components present in the following mixtures:
Name the components present in the following mixtures:
(a) Brass
(b) Duralumin
(c) Tap water
(d) Bronze
(a) Brass — Copper and zinc.
(b) Duralumin — Aluminium, copper, magnesium and manganese.
(c) Tap water — Water, dissolved salts, dissolved gases, minerals
(d) Bronze — Copper and tin.
Question 3Define the following with an example for each:
Define the following with an example for each:
(a) Pure substance
(b) Impure substance
(c) Alloy
(d) Solution
(e) Heterogeneous mixture
(f) Homogeneous mixture
(a) A pure substance is an element or compound containing only one kind of particle and having a definite composition and characteristic properties. Example: gold or distilled water.
(b) An impure substance, or mixture, contains two or more substances physically combined in any proportion. Example: air.
(c) A homogeneous solid mixture of two or more metals, or of a metal and a non-metal, is called an alloy. Example:
Brass: Copper + Zinc
Bronze: Copper + Tin
(d) A solution is a homogeneous mixture formed when a solute dissolves in a solvent. Example: salt solution.
(e) A heterogeneous mixture has constituents that are not uniformly distributed and may be seen separately. Example: sand and water.
(f) A homogeneous mixture has constituents uniformly distributed throughout and they cannot be seen separately. Example: salt solution.
Question 4Give one difference between pure substances and mixtures.
Give one difference between pure substances and mixtures.
One difference between a pure substance and a mixture is given below:
| Pure substance | Mixture |
|---|---|
| It contains only one kind of particle. | It contains two or more kinds of particles. |
| Example: Gold, sugar, etc. | Example: Air, honey, etc. |
Question 5What do you observe when a magnet is brought near a mixture of iron and sulphur?
What do you observe when a magnet is brought near a mixture of iron and sulphur?
Correct answerWhen a magnet is brought near a mixture of iron and sulphur, the magnetic iron filings are attracted to the magnet and are removed, leaving sulphur behind.
Practice section
Exercise I — Long Answer Type Questions
Question 1(a)Give reason: Why do sugar and water retain their individual properties in a sugar solution?
Give reason:
Why do sugar and water retain their individual properties in a sugar solution?
Correct answerSugar solution is a mixture. In a mixture, the components are loosely held together and do not undergo any chemical change. Therefore, sugar and water retain their individual properties in a sugar solution.
Question 1(b)Give reason: Why do petrol and water form a heterogeneous mixture?
Give reason:
Why do petrol and water form a heterogeneous mixture?
Correct answerPetrol and water form a heterogeneous mixture because they are immiscible liquids and do not mix uniformly. Petrol forms the upper layer because it is less dense than water.
Question 1(c)Give reason: Why does sulphur dissolve when carbon disulphide is added to a mixture of iron and sulphur but not when it is added to…
Give reason:
Why does sulphur dissolve when carbon disulphide is added to a mixture of iron and sulphur but not when it is added to iron sulphide?
Correct answerIn a mixture of iron and sulphur, the two substances are only physically mixed and retain their individual properties. Sulphur is still present as free sulphur, so it dissolves in carbon disulphide, leaving iron behind.
In iron sulphide, iron and sulphur are chemically combined to form a compound. Sulphur does not exist separately in iron sulphide, so it does not dissolve in carbon disulphide.
Question 2(a)State: Four differences between compounds and mixtures.
State: Four differences between compounds and mixtures.
Four differences between compounds and mixtures are given below:
| Compound | Mixture |
|---|---|
| A compound is a pure substance. | A mixture is an impure substance. |
| Compounds are always homogeneous. | Mixtures may be homogeneous or heterogeneous. |
| Properties of components are changed during the formation of a compound. | Mixtures retain the properties of its components. |
| Compounds have fixed melting points and boiling points. | Mixtures do not have fixed melting points and boiling points. |
Question 2(b)State: Four differences between water and air.
State: Four differences between water and air.
Four differences between water and air are given below:
| Water | Air |
|---|---|
| Water is a compound. | Air is a mixture. |
| Water is made up of hydrogen and oxygen in a fixed proportion by mass. | Air contains oxygen, nitrogen, carbon dioxide and water vapour, but they are not in a fixed proportion. Their amount varies from place to place. |
| The properties of water are completely different from those of its elements. | Air retains the properties of its component gases. |
| Water is represented by the molecular formula H2O. | Air cannot be represented by any formula. |
Question 3(a) Define 'mixture'.
(a) Define 'mixture'.
(b) List four characteristics of a mixture.
(a) A mixture is an impure substance formed by physically combining two or more pure substances in any proportion, without a chemical change, so that the components retain their individual properties.
(b) Four characteristics of a mixture:
A mixture contains two or more substances that are physically combined and not chemically bonded.
Mixtures do not have any fixed composition, i.e. they can have their components in varying proportions.
In mixtures, components are loosely held together and they retain their individual properties.
A mixture does not have a single definite set of physical properties.
Practice section
Exercise II — Objective Type Questions
Question 1(i)The process of adding a chemical substance to help the suspended solid particles to deposit as sediment faster is called:
The process of adding a chemical substance to help the suspended solid particles to deposit as sediment faster is called:
Correct answerloading
Reason: Helping fine suspended particles settle faster by adding a suitable chemical such as alum is called loading.
Sedimentation is the natural settling of particles at the bottom without adding any chemical. Decantation is the process of carefully pouring off the clear liquid after sedimentation. Filtration is the process of separating solids from liquids using a filter.
Question 1(ii)Salt is separated from sea water by:
Salt is separated from sea water by:
Correct answerevaporation
Reason: Salt from sea water is separated by evaporation. Sea water is collected in shallow beds and allowed to evaporate in the sun. When all the water is evaporated, salt is left behind.
Sublimation is used for substances that directly change from solid to gas (like camphor), not for salt in water. Magnetic separation is used to separate magnetic materials like iron, not salt. Filtration cannot separate dissolved substances like salt from water.
Question 1(iii)A gas dissolved in a liquid can be separated by:
A gas dissolved in a liquid can be separated by:
Correct answerboiling
Reason: A mixture of gas in liquid can be separated by heating or boiling. Dissolved gas escapes from the liquid on heating or boiling.
Filtration is used to separate insoluble solids from liquids, not dissolved gases. Magnet works only for magnetic materials like iron. Sublimation is used for solids that directly convert into gas, not for dissolved gases.
Question 1(iv)Camphor can be separated from a mixture of sand and camphor by:
Camphor can be separated from a mixture of sand and camphor by:
Correct answersublimation
Reason: Camphor can be separated from a mixture of sand and camphor by sublimation. The camphor sublimes and escapes as vapour, while the sand is left behind.
Filtration is used for separating solids from liquids, not two solids. Evaporation is used to separate dissolved solids from liquids, not solid-solid mixtures. Winnowing is used to separate lighter and heavier solids using air (like husk and grains), not suitable here.
Question 1(v)A separating funnel is used to separate:
A separating funnel is used to separate:
Correct answerimmiscible liquids
Reason: A separating funnel is a laboratory tool used to separate immiscible liquids. The denser liquid settles at the bottom, and the lighter one floats on top. When the stopcock is opened, the denser bottom layer drains first, separating the two liquids.
Miscible liquids mix completely (like alcohol and water), so they cannot be separated using a separating funnel. Sugar is dissolved in water, so this requires evaporation, not a separating funnel. This is a solid-liquid mixture and can be separated by filtration.
Practice section
Exercise II — Assertion Reason Type Questions
Question 2(i)Assertion: Mixtures cannot be represented by any chemical symbol or formula.
Mixtures cannot be represented by any chemical symbol or formula.
Mixtures neither have a uniform composition nor definite properties.
Correct answerBoth A and R are true and R is the correct explanation of A.
Reason: A is true as mixtures cannot be represented by any chemical symbol or formula.
R is true because mixtures do not have a fixed composition or a definite set of properties. Hence, the reason correctly explains the assertion.
Therefore, Both A and R are true and R is the correct explanation of A is the correct option.
Question 2(ii)Assertion: The process in which a solid on heating directly changes into its vapour, without changing into the liquid state is calle…
The process in which a solid on heating directly changes into its vapour, without changing into the liquid state is called sublimation.
Camphor and iodine can sublime.
Correct answerBoth A and R are true and R is not the correct explanation of A.
Reason: A is true as sublimation is a process where a solid directly changes into vapour without becoming liquid.
R is true as camphor and iodine can sublime.
Therefore, Both A and R are true and R is not the correct explanation of A is the correct option.
Question 2(iii)Assertion: Air retains the properties of its constituent gases.
Air retains the properties of its constituent gases.
Air is a mixture.
Correct answerBoth A and R are true and R is the correct explanation of A.
Reason: A is true as air shows the properties of its constituent gases (like oxygen supports combustion, nitrogen is inert, etc.).
R is true as air is a mixture.
Therefore, Both A and R are true and R is the correct explanation of A is the correct option.
Question 2(iv)Assertion: The insoluble solid from a solid-liquid heterogeneous mixture can be separated by filtration.
The insoluble solid from a solid-liquid heterogeneous mixture can be separated by filtration.
The substance left on the filter paper after filtration is called a filtrate.
Correct answerA is true and R is false.
Reason: A is true as an insoluble solid in a liquid (a heterogeneous mixture) can be separated by filtration.
R is false as the substance left on the filter paper is called the residue, while the liquid that passes through is called the filtrate.
Therefore, A is true and R is false is the correct option.
Practice section
Exercise II — Fill in the blank
Question 3Fill in the blanks:
Fill in the blanks:
(a) The substances that make a mixture are called its ............... or ............... .
(b) ............... is a process to separate solids dissolved in liquids.
(c) Mist is a ............... mixture of droplets of water and air.
(d) Clay is separated from water by the method of ............... .
(e) When cereals are washed before cooking, water is separated from the cereals by ............... .
(f) ............... is a process to obtain a very pure form of a solid dissolved in a liquid.
(g) Ammonium chloride can be separated from common salt by the method of ............... .
(h) The solid particles which remain on the filter paper are called ............... and the liquid which passes through it is called ............... .
(i) The process of transferring the clear liquid above the solid particles which settle at the bottom of the container is known as ............... .
(j) ............... is a method used for the separation of an insoluble solid from a solid-liquid mixture.
(a) The substances that make a mixture are called its components or constituents.
(b) Evaporation is a process to separate solids dissolved in liquids.
(c) Mist is a heterogeneous mixture of droplets of water and air.
(d) Clay is separated from water by the method of filtration.
(e) When cereals are washed before cooking, water is separated from the cereals by decantation.
(f) Crystallisation is a process used to obtain a pure solid in the form of crystals from its solution.
(g) Ammonium chloride can be separated from common salt by the method of sublimation.
(h) The solid particles which remain on the filter paper are called residue and the liquid which passes through it is called filtrate.
(i) The process of transferring the clear liquid above the solid particles which settle at the bottom of the container is known as decantation.
(j) Filtration is a method used for the separation of an insoluble solid from a solid-liquid mixture.
Practice section
Exercise II — State True or False
Question 4Write "true" or "false" for the following statements:
Write "true" or "false" for the following statements:
(a) A pure substance consists of only one kind of atom or molecule. ...............
(b) The components of a mixture are present in a fixed ratio. ...............
(c) Common salt is separated from its solution in water by decantation. ...............
(d) Winnowing is a process to remove small stones from grains. ...............
(e) Gold jewellery is a homogeneous mixture of metals. ...............
(f) Air can be separated from water by filtration. ...............
(g) Salt and air dissolved in water add taste to water. ...............
(h) Steel is an alloy of iron and aluminium. ...............
(a) True
(b) False
Correct statement: A mixture has no fixed composition, i.e. it is formed by mixing two or more substances in any ratio without any chemical reaction.
(c) False
Correct statement: Common salt is separated from its solution in water by evaporation.
(d) False
Correct statement: Winnowing removes lighter husk from heavier grains, whereas, small stones are removed by hand picking or sieving.
(e) True
(f) False
Correct statement: Air can be separated from water by heating or boiling.
(g) True
(h) False
Correct statement: Steel is an alloy of iron and carbon.
Practice section
Exercise II — Match the Following
Question 5Match the following:
Match the following:
| Column A | Column B |
|---|---|
| (a) Heterogeneous mixture | (i) Homogeneous substance |
| (b) Evaporation | (ii) Rice from husk |
| (c) Sublimation | (iii) Iron and sulphur |
| (d) Compounds | (iv) Sea Water |
| (e) Winnowing | (v) Ammonium chloride and salt |
| Column A | Column B |
|---|---|
| (a) Heterogeneous mixture | (iii) Iron and sulphur |
| (b) Evaporation | (iv) Sea Water |
| (c) Sublimation | (v) Ammonium chloride and salt |
| (d) Compounds | (i) Homogeneous substance |
| (e) Winnowing | (ii) Rice from husk |
Practice section
Exercise II — One Word Answer Type Questions
Question 6Give one word for the following:
Give one word for the following:
(a) The solid which is left on the filter paper after filtration.
(b) The solid particles which separate out from the solution on slow evaporation.
(c) The solid particles that settle at the bottom of the beaker in a heterogeneous mixture of a solid and a liquid.
(d) The clear liquid which is poured out after sedimentation.
(e) The technique used to separate the light particles from heavy particles using the flow of wind.
(a) Residue
(b) Crystals
(c) Sediment
(d) Supernatant liquid
(e) Winnowing
Question 7Name the process by which the components of the following mixtures can be separated.
Name the process by which the components of the following mixtures can be separated.
(a) Powdered glass and sugar
(b) Chalk powder and iron filings
(c) Chaff and grain
(d) Salt and water
(e) Wheat and sugar
(f) Sand and camphor
(g) Sugar and water
(a) Dissolve the sugar in water, filter out the powdered glass, and then recover the sugar by evaporation or crystallisation
(b) Magnetic separation
(c) Winnowing
(d) Evaporation
(e) Sieving
(f) Sublimation
(g) Evaporation
Practice section
Exercise II — Rearrange the Following
Question 8Rearrange the following to get meaningful words:
Rearrange the following to get meaningful words:
(all are methods to separate the components of mixtures).
(a) OIRATVOPEAN
(b) DNOITITLLIAS
(c) FTOLINTRAI
(d) SINIVEG
(a) EVAPORATION
(b) DISTILLATION
(c) FILTRATION
(d) SIEVING
Practice section
Exercise II — Short Answer Type Questions
Question 1Name: (a) two substances which can sublime
Name:
(a) two substances which can sublime
(b) two substances soluble in water
(c) two substances insoluble in water
(d) four substances that can be used as filters.
(a) Two substances which can sublime:
Camphor
Naphthalene
(b) Two substances soluble in water:
Sugar
Salt
(c) Two substances insoluble in water:
Sand
Sawdust
(d) Four substances used as filters:
Layer of sand
Charcoal
Cotton
Filter paper
Question 2Give one example for each of the following types of mixtures.
Give one example for each of the following types of mixtures.
(a) Solid-solid heterogeneous mixture
(b) Solid-liquid heterogeneous mixture
(c) Solid-liquid homogeneous mixture
(a) Rice and husk
(b) Chalk powder and water
(c) Salt solution
Question 3Define: (a) Filtration
Define:
(a) Filtration
(b) Sublimation
(c) Evaporation
(d) Sedimentation
(e) Decantation
(f) Distillation
(a) The process of separating insoluble solid particles from a liquid by allowing it to pass through a filter is called filtration.
(b) The process in which a solid changes directly into its vapour on heating without changing into its liquid state is called sublimation.
(c) Evaporation is the process of converting a liquid into its vapour state, either by exposing it to air or by heating.
(d) The settling down of suspended, insoluble, heavy solid particles in a solid-liquid mixture when left undisturbed is called sedimentation.
(e) The process of pouring out the clear liquid, without disturbing the sediment, is called decantation.
(f) Distillation is the method of getting a pure liquid from a solution by evaporating and then condensing the vapours.
Practice section
Exercise II — Long Answer Type Questions
Question 1Why do we need pure substances?
Why do we need pure substances?
We need pure substances because of the following reasons:
Impurities in food, water, or cosmetics can cause allergic reactions, poisoning, or contamination.
Pure substances have fixed boiling and melting points, making them reliable for calibration and standards. Whereas, mixtures often have variable physical properties.
Pure substances have a known chemical composition, which is critical when calculating concentrations, dosages, or reactions.
In industries like pharmaceuticals, electronics, and food production, impurities can ruin a product or make it unsafe.
Question 2(a)Give reason: Sand and sawdust cannot be separated by hand picking.
Give reason:
Sand and sawdust cannot be separated by hand picking.
Correct answerHandpicking is suitable only when the unwanted particles are large and easily distinguishable. Sand and sawdust contain many small particles, so separating them one by one by hand is impractical.
Question 2(b)Give reason: Magnet is used to separate a mixture of iron and sulphur.
Give reason:
Magnet is used to separate a mixture of iron and sulphur.
Correct answerIn magnetic separation, a magnet is moved over the mixture. Iron is magnetic and is attracted to the magnet, while sulphur is not.
Question 2(c)Give reason: Alum is used in purification of river water.
Give reason:
Alum is used in purification of river water.
Correct answerWater from a river contains very fine clay particles. To make them settle at a faster rate, a chemical substance called alum in powdered form is added to such mixtures. Alum helps the fine clay and dust particles clump together into heavier particles, increasing the rate of sedimentation.
Question 3Study the evaporation diagram and answer the following questions:
Study the evaporation diagram and answer the following questions:
(a) Label the parts shown as A, B and C.
(b) Write the name of the method depicted above.
(c) What kind of mixture is separated by this method?
(d) How can this process be made faster?
(e) What is one disadvantage of this process?
Replace this dummy image with the labelled evaporation diagram.
(a) The parts shown as A, B, and C indicate the following:
A→Liquid
B→Evaporating dish
C→Bunsen burner
(b) Evaporation is depicted in the given picture.
(c) Homogeneous solid-liquid mixture is separated by this method.
(d) Evaporation can be made faster by heating.
(e) In the evaporation process, the solvent is lost to the surroundings as vapour and cannot be collected.
Practice section
Case Study Type Questions
Question 1Zainab was helping her mother in the kitchen. She took some rice grains in a bowl, which also contained a few small stones to sort.…
Zainab was helping her mother in the kitchen. She took some rice grains in a bowl, which also contained a few small stones to sort. By mistake, she dropped a container of salt into the bowl, and salt got mixed with the rice grains. Her mother then asked her to separate the rice grains from the stones and the salt so that the rice would be clean and ready to cook for dinner later.
(a) What kind of mixture was formed by Zainab? Justify your answer.
(b) How will you separate the stones from the mixture? Name the method used.
(c) What do you observe when water is added to the remaining mixture of rice grains and salt?
(d) What will you do to separate rice grains from water?
(e) How will you recover the dissolved salt from the solution?
(a) The mixture formed is a heterogeneous mixture. Rice grains, small stones and salt are not uniformly mixed and can be seen separately before water is added.
(b) Stones can be separated by handpicking.
This method works because stones are visibly different in size, shape, and color from rice grains.
(c) When water is added, the salt dissolves in water forming a salt solution, while the rice grains remain undissolved and settle down.
(d) Rice can be separated from water by decantation (pouring off the water).
(e) The dissolved salt can be recovered by evaporation. When the solution is heated or left to evaporate, water evaporates and the salt remains behind as a solid.
Frequently Asked Questions
Use these quick answers for revision before opening the detailed exercises.
What is a pure substance?
A pure substance contains only one kind of particle and has a definite composition and characteristic properties. Elements and compounds are pure substances.
What is a mixture?
A mixture is formed when two or more substances are physically combined in any proportion without a chemical change, so the components retain their properties.
What is the difference between homogeneous and heterogeneous mixtures?
A homogeneous mixture is uniform throughout, while a heterogeneous mixture is not uniform and its components may be seen separately.
How can salt be separated from seawater?
Salt can be obtained from seawater by evaporation. Crystallisation can be used when purer crystals are required.
What is filtration?
Filtration separates an insoluble solid from a liquid by passing the mixture through a filter. The solid left behind is residue and the liquid that passes through is filtrate.
What is sublimation?
Sublimation is the direct change of a solid into vapour on heating without passing through the liquid state. Camphor and ammonium chloride can sublime.
Why is a separating funnel used?
A separating funnel separates immiscible liquids, such as oil and water, by allowing the denser lower liquid to drain first.
Why is alum added during water purification?
Alum helps very fine suspended particles clump together into heavier particles so that they settle faster during sedimentation.
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