These NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.
Is Matter Around Us Pure NCERT Solutions for Class 9 Science Chapter 2
Class 9 Science Chapter 2 Is Matter Around Us Pure InText Questions and Answers
Question 1.
What is meant by a pure substance?
Answer:
A pure substance is the one that consists of a single type of particles, i.e., all constituent particles of the substance have the same chemical nature. Pure substances can be classified as elements or compounds.
Question 2.
List the points of differences between homogeneous and heterogeneous mixtures.
Answer:
A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example: salt in water, sugar in water, copper sulphate in water.
A heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example: sodium chloride and iron fillings, salt and sulphur, oil and water
Question 3.
Differentiate between homogeneous and heterogeneous mixtures with examples.
Answer:
A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example, mixtures of salt in water, sugar in water, copper sulphate in water, iodine in alcohol, alloy, and air have uniform compositions throughout the mixtures.
On the other hand, a heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example, composition of mixtures of sodium chloride and iron fillings, salt and sulphur, oil and water, chalk powder in water, wheat flour in water, milk and water are not uniform throughout the mixtures.
Question 4.
How are sol, solution and suspension different from each other?
Answer:
Sol is a heterogeneous mixture. In this mixture, the solute particles are so small that they cannot be seen with the naked eye. Also, they seem to be spread uniformly throughout the mixture. The Tyndall effect is observed in this mixture. For example; milk of magnesia, mud.
Solution is a homogeneous mixture. In this mixture, the solute particles dissolve and spread uniformly throughout the mixture. The Tyndall effect is not observed in this mixture. For example: salt in water, sugar in water, iodine in alcohol, alloy
Suspensions are heterogeneous mixtures. In this mixture, the solute particles are visible to the naked eye, and remain suspended throughout the bulk of the medium. The Tyndall effect is observed in this mixture. For example: chalk powder and water, wheat flour and water
Question 5.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Answer:
Mass of solute (sodium chloride)=36 g (Given)
Mass of solvent (water) = 100 g (Given)
Then, mass of solution = Mass of solute + Mass of solvent
= (36 + 100) g
= 136 g
= \(\frac{\text { Mass of solute }}{\text { Mass of solvent }}\) × 100%
= \(\frac{36}{136}\) × 100%
= 26.47%
Therefore, concentration (mass by mass percentage) of the solution.
Question 6.
Classify the following as chemical or physical changes:
- Cutting of trees
- Melting of butter in a pan
- Rusting of almirah
- Boiling of water to form steam
- Passing of electric current through water, and water breaking down into hydrogen and oxygen gas
- Dissolving common salt in water
- Making a fruit salad with raw fruits
- Burning of paper and wood
Answer:
- Cutting of trees ? Physical change
- Melting of butter in a pan ? Physical change
- Rusting of almirah ? Chemical change
- Boiling of water to form steam ? Physical change
- Passing of electric current through water, and water breaking down into hydrogen and oxygen gas ? Chemical change
- Dissolving common salt in water ? Physical change
- Making a fruit salad with raw fruits ? Physical change
- Burning of paper and wood ? Chemical change
Question 7.
Try segregating the things around you as pure substances or mixtures.
Answer:
Pure substance: Water, salt, sugar
Mixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food
Question 8.
What type of mixtures is separated by the technique of crystallization?
Answer:
By the technique of crystallization, pure solids are separated from impurities. For example, salt obtained from the sea is separated from impurities; crystals of alum (Phitkari) are separated from impure samples.
Class 9 Science Chapter 2 Is Matter Around Us Pure Textbook Questions and Answers
Question 1.
Which separation techniques will you apply for the separation of the following?
(a) Sodium chloride from its solution in water.
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(c) Small pieces of metal in the engine oil of a car.
(d) Different pigments from an extract of flower petals.
(e) Butter from curd.
(f) Oil from water.
(g) Tea leaves from tea.
(h) Iron pins from sand.
(i) Wheat grains from husk.
(j) Fine mud particles suspended in water.
Answer:
(a) Sodium chloride from its solution in water ? Evaporation
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride ? Sublimation
(c) Small pieces of metal in the engine oil of a car ? Centrifugation or filtration or decantation
(d) Different pigments from an extract of flower petals ? Chromatography
(e) Butter from curd ? Centrifugation
(f) Oil from water ? Using separating funnel
(g) Tea leaves from tea ? Filtration
(h) Iron pins from sand ? Magnetic separation
(i) Wheat grains from husk ? Winnowing
(j) Fine mud particles suspended in water ? Centrifugation
Question 2.
Write the steps you would use for making tea. Use the words: solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Answer:
First, water is taken as a solvent in a saucer pan. This water (solvent) is allowed to boil. During heating, milk and tea leaves are added to the solvent as solutes. They form a solution. Then, the solution is poured through a strainer. The insoluble part of the solution remains on the strainer as residue. Sugar is added to the filtrate, which dissolves in the filtrate. The resulting solution is the required tea.
Question 3.
Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).
(a) What mass of potassium nitrate would be needed to produce a saturated solution of
potassium nitrate in 50 grams of water at 313 K?
(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
(c) Find the solubility of each salt at 293 K. What salt has the highest solubility at this temperature?
(d) What is the effect of change of temperature on the solubility of a salt?
Answer:
(a) At 313 K, 62 grams of Potassium nitrate dissolved in 100 grams of water. So to produce a saturated solution of potassium nitrate in 50 grams of water, we need
\(\frac{62 \times 50}{100}\) = 31 grams of potassium nitrate
(b) Some soluble potassium chloride will separate out in the form of crystals at room temperature because the solubility of potassium chloride will decrease with decrease in temperature.
(c) (i) Solubility of Potassium nitrate at 293 K is 32 grams.
(ii) Solubility of Sodium chloride at 293 K is 36 grams.
(iii) Solubility of Potassium chloride at 293 K is 35 grams.
(iv) Solubility of Ammonium chloride at 293 K is 37 grams.
The solubility of Ammonium chloride is highest at this temperature.
(d) The solubility of salt increases with increase in temperature.
Question 4.
Explain the following giving examples:
(a) Saturated solution
(b) Pure substance
(c) Colloid
(d) Suspension
Answer:
(a) Saturated solution: A saturated solution is a solution in which the maximum amount of solute has been dissolved at a given temperature. The solution cannot dissolve beyond that amount of solute at that temperature. Any more solute added will settle down at the bottom of the container as a precipitate.
Suppose 500 g of a solvent can dissolve a maximum of 150 g of a particular solute at 40°C. Then, the solution obtained by dissolving 150 g of that solute in 500 g of that solvent at 300 K is said to be a saturated solution at 300 K.
(b) Pure substance: A pure substance is a substance consisting of a single type of particles i. e., all constituent particles of the substance have the same chemical properties.
For example, salt, sugar, water are pure substances.
(c) Colloid: A colloid is a heterogeneous mixture. The size of the solutes in this mixture is so small that they cannot be seen individually with naked eyes, and seems to be distributed uniformly throughout the mixture. The solute particles do not settle down when the mixture is left undisturbed. This means that colloids are quite stable. Colloids cannot be separated by the process of filtration. They can be separated by centrifugation. Colloids show the Tyndall effect. For example, milk, butter, foam, fog, smoke, clouds.
(d) Suspension: Suspensions are heterogeneous mixtures. The solute particles in this mixture remain suspended throughout the bulk of the medium. The particles can be seen with naked eyes. Suspension shows the Tyndall effect. The solute particles settle down when the mixture is left undisturbed. This means that suspensions are unstable. Suspensions can be separated by the method of filtration. For example, mixtures of chalk powder and water, wheat flour and water.
Question 5.
Classify each of the following as a homogeneous or heterogeneous mixture. Soda water, wood, air, soil, vinegar, filtered tea
Answer:
Homogeneous mixtures: Soda water, air, vinegar
Heterogeneous mixtures: Wood, soil, filtered tea
Question 6.
How would you confirm that a colourless liquid given to you is pure water?
Answer:
Every liquid has a characteristic boiling point. Pure water has a boiling point of 100°C (373 K) at 1 atmospheric pressure. If the given colourless liquid boils at even slightly above or below 100°C, then the given liquid is not pure water. It must boil at sharp 100°C. Thus, by observing the boiling point, we can confirm whether a given colourless liquid is pure water or not.
Question 7.
Which of the following materials fall in the category of a “pure substance”?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric Acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air
Answer:
The following materials fall in the category of a “pure substance”:
(a) Ice
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
Question 8.
Identify the solutions among the following mixtures:
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water
Answer:
The following mixtures are solutions:
(b) Sea water
(c) Air
(e) Soda water
Question 9.
Which of the following will show the “Tyndall effect”?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution
Answer:
Milk and starch solution will show the “Tyndall effect”.
Question 10.
Classify the following into elements, compounds and mixtures:
(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
(h) Coal
(i) Air
(j) Soap
(k) Methane
(l) Carbon dioxide
(m) Blood
Answer:
Elements:
(a) Sodium
(d) Silver
(f) Tin
(g) Silicon
Compounds:
(e) Calcium carbonate
(k) Methane
(l) Carbon dioxide
Mixtures:
(b) Soil
(c) Sugar solution
(h) Coal
(i) Air
(j) Soap
(m) Blood
Question 11.
Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron fillings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of candle
Answer:
The following changes are chemical changes:
(a) Growth of a plant
(b) Rusting of iron
(d) Cooking of food
(e) Digestion of food
(g) Burning of candle
Class 9 Science Chapter 2 Is Matter Around Us Pure Additional Important Questions and Answers
Multiple Choice Questions
Choose the correct option:
Question 1.
Which of the following statements are true for pure substances?
(i) Pure substances contain only one kind of particles
(ii) Pure substances may be compounds or mixtures
(iii) Pure substances have the same com-position throughout
(iv) Pure substances can be exemplified by all elements other than nickel
(a) (i) and (ii)
(b) (i) and (iii)
(c) (iii) and (iv)
(d) (ii)and (iii)
Answer:
(b) (i) and (iii)
Question 2.
Rusting of an article made up of iron is called
(a) corrosion and it is a physical as well as chemical chang
(b) dissolution and it is a physical change
(c) corrosion and it is a chemical change
(d) dissolution and it is a chemical change
Answer:
(c) corrosion and it is a chemical change
Question 3.
A mixture of sulphur and carbon disulphide is
(a) heterogeneous and shows Tyndall effect
(b) homogeneous and shows Tyndall effeet
(c) heterogeneous and does not show Tyndall effect
(d) homogeneous and does not show Tyndall effect
Answer:
(d) homogeneous and does not show Tyndall effect
Question 4.
Tincture of iodine has antiseptic properties. This solution is made by dissolving
(a) iodine in potassium iodide
(b) iodine in vaseline
(c) iodine in water
(d) iodine in alcohol
Answer:
(d) iodine in alcohol
Question 5.
Which of the following are homogeneous in nature?
(i) ice
(ii) wood
(iii) soil
(iv) air
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i) and (iv)
(d) (iii) and (iv)
Answer:
(c) (i) and (iv)
Question 6.
Which of the following are physical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal
(a) (i), (ii) and (iii)
(b) (i), (ii) and (iv)
(c) (i), (iii) and (iv)
(d) (ii), (iii) and (iv)
Answer:
(c) (i), (iii) and (iv)
Question 7.
Which of the following are chemical changes?
(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer:
(a) (i) and (ii)
Very Short Answer Type Questions
Question 1.
Define solvent.
Answer:
The component of the solution that dissolves the other component in it is called the solvent.
Question 2.
Define solute.
Answer:
The component of the solution that is dissolved in the solvent is called solute.
Question 3.
What is ’tincture of iodine’?
Answer:
A solution of iodine in alcohol is known as tincture of iodine. It has iodine (splid) as the solute and alcohol (liquid) as the solvent.
Question 4.
What are alloys?
Answer:
The homogeneous mixture of two or more metals or a metal and non-metal is called an alloy. E.g., steel is an alloy of iron and carbon.
Question 5.
Give one example of gas in liquid , solution.
Answer:
Cold-drinks, carbon dioxide gas as solute is mixed with water as a solvent.
Question 6.
How can a solution be dilute or concentrated?
Answer:
The amount of solute dissolved in a solvent decides whether the solution is dilute or concentrated.
Question 7.
What is “concentration of a solution”?
Answer:
The concentration of a solution is the amount of solute present in a given amount of solution or the amount of solute dissolved in a given mass or volume of solvent.
Question 8.
State the difference between aqueous and non-aqueous solution.
Answer:
Aqueous solutions have water as solvent and non-aqueous solutions do not have water as solvent.
Question 9.
What is “solubility” of a solute?
Answer:
The amount of the solute present in the saturated solution at the given temperature is called its solubility.
Question 10.
What is saturated solution?
Answer:
The maximum amount of solute that ‘ can be dissolved in a solvent at given temperature is called saturated solution, where no more solute can dissolve further.
Question 11.
What is unsaturated solution?
Answer:
If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.
Question 12.
How can you convert saturated solution into unsaturated or vice-versa?
Answer:
Saturated solution on heating becomes unsaturated and unsaturated solution on cooling becomes saturated.
Question 13.
Why water is called universal solvent?
Answer:
Water can dissolve large number of substances in it.
Question 14.
What is Tyndall effect?
Answer:
The scattering of light by colloidal particles is known as Tyndall effect.
Question 15.
How can we separate colloidal mixtures?
Answer:
By centrifugation, in a centrifuge machine the colloidal solution is kept in a test tube, rotated very fast and due to centrifugal force’ the colloidal particles are separated.
Question 16.
What is emulsion?
Answer:
When both the dispersed phase and dispersing medium is liquid, it is called emulsion. E.g., milk, face cream.
Question 17.
What is aerosol?
Answer:
When the solid or liquid is dispersed in a gas if Is called aerosol. E.g., smoke, fog. .
Question 18.
What is the principle for separation of immiscible liquids?
Answer:
The principle of separating immiscible liquids into layers depends on their densities. The less denser liquid collects at the top and more denser liquid at- the bottom.
Question 19.
What is chromatography?
Answer:
Chromatography is the technique used for separation of those solutes that dissolve in the same solvent.
Question 20.
What is distillation?
Answer:
Distillation is the separation technique of two miscible liquids that boils without decomposition and have sufficient difference in their boiling points.
Question 21.
How can you separate two liquids that have less than 25 K difference of boiling points?
Answer:
To separate a mixture of two or more miscible liquids for which the difference in boiling points is less than 25 K, is fractional distillation.
Question 22.
What is condenser?
Answer:
It is an apparatus used to convert gas into liquid by cooling it.
Question 23.
What is crystallisation?
Answer:
When a saturated solution is heated and allowed to cool slowly, crystal of the solute dissolved in die saturated solution are separated from it. It is used to purify solids.
Question 24.
How will you separate miscible and immiscible liquids?
Answer:
Miscible liquid can be separated by distillation and immiscible liquids can be separated by using separating funnel.
Short Answer Type questions
Question 1.
Why is mixture called impure substance?
Answer:
Mixture consists of different components which retain their properties and can be easily separated by physical processes, hence it is called as impure substance.
Question 2.
Give the differences between mixture and compound.
Answer:
Mixture:
- Constituents combine in any rato to form mixture.
- Constituents retain their properties.
- Constituents can be separated by physical processes.
Compound:
- Constituents combine in fixed ratio to form a compound.
- Constituents do not retain their properties
- Constituents cannot be separated by physical processes.
Question 3.
Distinguish between a physical change and chemical change.
Answer:
Physical Change:
- No new substance is formed.
- It is a reversible change.
- The properties of constituents are retained.
- No new substance is formed.
Chemical Change:
- New substance is formed.
- It is irreversible change.
- The properties of constituents are not retained.
- Completely new substance is formed.
Question 4.
State the properties of a solution.
Answer:
Properties of a solution are:
- A solution is a homogeneous mixture.
- Particles of a solution are smaller than 1 nm and cannot be seen by naked eyes.
- Do not scatter beam of light.
- Solute particles cannot be separated from the mixture by the process of filtration and thus, solution is stable.
Question 5.
State the properties of a suspension.
Answer:
Properties of a suspension:
- Suspension is a heterogeneous mixture having particle size greater than 100 nm.
- The particles of a suspension can be seen by naked eyes.
- Particles can scatter a beam of light.
- It is unstable.
Question 6.
What is a colloidal solution?
Answer:
It is a heterogeneous solution which appears to be homogeneous, particles size is very small and so cannot be seen with naked eyes but it is stable. E.g., milk and blood.
Question 7.
State the properties of colloidal solution.
Answer:
Properties of colloidal solution.
- It is a heterogeneous mixture having particle size between 1 nm to 100 nm.
- Size of particles is very small, cannot be seen with naked eyes.
- It scatters a beam of light.
- They are stable as the particles do not settle when left undisturbed.
Question 8.
Give the applications of centrifugation.
Answer:
Application of centrifugation are:
- Used in diagnostic laboratories for blood and urine test.
- Used in dairies and home to separate butter from cream.
- Used in washing machines as. a spinner to squeeze out water from wet clothes.
Question 9.
Give the applications of chromatography.
Answer:
Applications of chromatography are
- To separate colours in a dye.
- To separate pigments from natural colours.
- To separate drugs from blood.
Question 10.
Why is crystallisation better than evaporation?
Answer:
Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.
Crystallisation is better than evaporation because during evaporation
- Some solids decompose or some, like sugar may get charred on heating to dryness.
- Some impurities may remain dissolved in the solution even after filtration which on evaporation contaminates the solid.
Question 11.
How will you separate a mixture of oil and water?
Answer:
To separate a mixture of oil and water, we need a separating funnel as both are immiscible liquids.
Pour the mixture in separating funnel and let the funnel stand undisturbed for sometime. So that separate layer of oil and water are formed. Open the stopcock of the separating funnel and pour out the lower layer of water carefully.
Question 12.
A student is given a mixture of naphthalene ball’s powder and common salt. He need to separate this mixture. How will he do this?
Answer:
The properties of both naphthalene and common salt should be known, before we choose the separation technique.
Naphthalene is a sublimate which on heating changes to gaseous state directly. Hence to separate a volatile compound (sublimate) from a non-volatile compound (non-sublimate), the sublimation process is used.
In a China dish the mixture is kept, and is placed on a stand. An inverted funnel is kept over the mixture in China dish with plugged stem. The sublimate on heating gets collected on the funnel and common salt remains in the China dish.
Question 13.
How can we obtain different gases from air?
Answer:
Air is a homogeneous mixture and its components can be separated by fractional distillation.
Question 14.
How can you prove that water is a compound?
Answer:
When electricity is passed through water at two different electrodes, we get two different gases i.e., oxygen and hydrogen during electrolysis of water are produced. The ratio of oxygen: hydrogen is 1 : 2 by number of molecules.
- The properties of oxygen and hydrogen gases are entirely different from that of liquid water.
- The ratio of oxygen: hydrogen combination is always constant i.e., 1 : 2 by volume.
- To separate the components of water, we need electrolytic cell, and it is not a simple process.
- This proves that water is a compound.
Question 15.
How can we convert saturated solution into unsaturated by heating?
Answer:
Saturated solution is said to be saturated at a given temperature when there is no more scope of solute particles to dissolve/dissociate into water. It is because the solute particle has taken all the intermolecular space present in the solvent. On heating, the molecules of solvent gain kinetic energy, start vibrating and try to move away from each other thereby accommodating some more solute particle in fids space and hence it becomes an unsaturated solution.
Question 16.
What is the difference in fog and smoke?
Answer:
Fog is a colloidal solution with liquid dispersed in gas. Smoke is a colloidal solution with solid dispersed in gas.
Question 17.
If 20 g of salt is present is 220 g of solution, calculate the concentration of solution.
Answer:
Concentration of solution
= \(\frac{\text { Mass of solute }}{\text { (Mass of solute + Mass of solvent) }}\)
Mass solute = 20 g
Mass of solute + solvent = 220 g
∴ Concentration of solution
= \(\frac{20}{220}\) × 100 = 9.09%
Question 18.
In Chromatography: Sometimes a spot will remain on the baseline, where sample was first applied:
(a) Suggest what affinity this substance would have for solvent.
(b) Suggest the value for Rf of this substance.
(c) Outline how you could determine whether these materials are pure or a mixture?
Answer:
(a) The spot on the base line is not soluble in the solvent.
(b) Its Rf value is 0.
(c) The solvent can be changed, only such solvent should be used in which the given sample can travel. The pure substances always have rf value less than 1.
Question 19.
Some students proposed measuring the position of each spot from the top, others proposed from the center. Explain which method is better?
Answer:
To measure the distance travelled by the spot it is always advisable to measure the distance from the base line. The measurement from the center will not give the correct value of Rf.
Question 20.
Distinguish between the pure and impure substances.
Answer:
Pure substance have fixed boiling and melting point arid the impure substances boil or melt over the range of the temperature.
Question 21.
On adding impurity to a substance what happens to its Boiling point/ Melting point?
Answer:
The boiling point and the melting point does not remain fixed. The boiling point increases on addition of impurity.
Question 22.
Pure ethanol boils at 78.4° C and freezes at -114.3° C. You have a sample of ethanol which boils between 79.1° C and 79.9° C
(a) What can you say about its purity?
(b) What will you expect to find, when you measure its freezing point?
Answer:
(a) The sample is impure as it is boiling over a range of temperature.
(b) The freezing point will lower.
Question 23.
It is important that some substances are pure. Give two examples.
Answer:
Pure substances are required for several things in life like medicine and food should be pure if impurities are added into it can become fatal.
Long Answer Type questions
Question 1.
Give the difference between true solution, colloidal solution and suspension.
Answer:
The difference between true solution, colloidal solution and suspension
Question 2.
State the different types of colloids with examples.
Answer:
Different colloids are formed due to different dispersed phase and dispersing medium.
Question 3.
(a) Define solution.
(b) Give different types of solutions with one example each.
Answer:
(a) Solution: It is a homogeneous mixture of two or more substances. It consists of solute and solvent.
(b) Different types of solution:
(i) Based on solvent-aqueous and non-aqueous
Aqueous solution has water as solvent (sugar + water)
Non-aqueous solution has some other solvent but not water. Example, (sulphur + carbon disulphide)
(ii) Depending on the amount of solute dissolved in solvent-Dilute solution and con centrated solution.
Dilute solution-Less amount of solute particles are present in a solvent. Concentrated solution-Amount of solute present in its maximum capacity in a solvent.
(iii) Amount of solute present in its maximum capacity at a given temperature-Saturated
and unsaturated solution.
Saturated solution-It is a solution in which no more solute can further dissolve in a given solvent at a given temperature.
Unsaturated solution-It is a solution in which sorne more salute can dissolve in a solvent at a given temperature.
Question 4.
How can you separate the following mixtures?
(a) Sand + iron
(b) Cream from milk
(c) Salt + water
(d) AmmonIum chloride + NaCl
(e) Copper sulphate + water
(f) Rice and dal (uncooked)
(g) Gases from air
(h) Petrol and diesel from crude oil
(i) Drugs from blood
(j) Acetone from water
Answer:
(a) Sand + iron – magnetic separation
(b) Cream from milk – centrifugation
(c) Salt + water – evaporation
(d) Ammonium chloride + NaCl – sublimation
(e) Copper sulphate + water – crystallisation
(f) Rice and dal (uncooked) – hand picking
(g) Gases from air – fractional distillation
(h) Petrol and diesel from crude oil – fractional distillation
(i) Drugs from blood – chromatography
(j) Acetone from water – distillation
Question 5.
A metal coin is dissolved in acid. Chromatography is used to test the solution formed. The diagram given shows the chromatogram obtained.
(a) Describe how the chromatogram would be set up in the laboratory.
(b) What can you say about the composition of the coin?
(c) Which of the spots (A, B or C ) is more soluble in the solvent that was used in the chromatography?
Answer:
(a) To set up the chromatogram use the solvent, take chromatography paper and draw the base line with pencil, place the spot of the chromatogram on this line and dip it in the solvent such that the base line of the paper stays above the solvent line.
(b) The coin consists of three different materials as the chromatogram shows three spots.
(c) The spot B is more soluble in the solvent as it travelled the maximum distance.
Question 6.
Compare the simple distillation and fractional distillation.
Answer:
Simple distillation: The distillation flask is used to separate two substances having the difference in their boiling point more than 23 degrees.
Fractional distillation: The fractionating column in the set up helps in the separation of the fractions which may have very low difference in their boiling point. The fractionating column is a long chamber which controls the separation of one fraction at a time starting from the one with the lowest boiling point.