Q 1. A homogeneous mixture of two or more substances is called a:
a) Compound
b) Solution
c) Element
d) Suspension
(b) Solution
Q 2. The component of a solution present in a larger amount is called:
a) Solute
b) Solvent
c) Colloid
d) Residue
b) Solvent
Q 3. Which of the following shows the Tyndall effect?
a) Salt solution
b) Sugar solution
c) Colloid
d) Copper sulphate solution
c) Colloid
Q 4. Which method is used to separate cream from milk?
a) Distillation
b) Centrifugation
c) Sublimation
d) Chromatography
b) Centrifugation
Q 5. The process of converting vapour into liquid is called:
a) Evaporation
b) Sublimation
c) Condensation
d) Filtration
c) Condensation
Q 6. Which of the following is a compound?
a) Air
b) Brass
c) Water
d) Soil
c) Water
Q 7. The separation of coloured components from ink is done by:
a) Filtration
b) Evaporation
c) Chromatography
d) Handpicking
c) Chromatography
Q 8. Which of the following is a heterogeneous mixture?
a) Salt solution
b) Air
c) Brass
d) Sand and water
d) Sand and water
Q 9. A substance made up of two or more substances mixed together is called a:
a) Element
b) Compound
c) Mixture
d) Atom
c) Mixture
Q 10. Which method is used to separate cream from milk?
a) Filtration
b) Centrifugation
c) Sublimation
d) Distillation
b) Centrifugation
Q 11. The process of separating insoluble solids from liquids using a filter paper is called:
a) Evaporation
b) Condensation
c) Filtration
d) Crystallisation
c) Filtration
Q 12. Which method is used to obtain salt from seawater?
a) Filtration
b) Evaporation
c) Centrifugation
d) Sublimation
b) Evaporation
Q 13. Brass is a mixture of:
a) Copper and zinc
b) Iron and carbon
c) Gold and silver
d) Copper and tin
a) Copper and zinc
Q 14. Which of the following mixtures shows the Tyndall effect?
a) Salt solution
b) Sugar solution
c) Colloid
d) Distilled water
c) Colloid
Q 15. Which technique is used to separate different colours in ink?
a) Filtration
b) Chromatography
c) Distillation
d) Handpicking
b) Chromatography
Q 16. Fill in the Blanks:
a) A homogeneous mixture of two or more metals is called an __________.
b) The particles of a true solution are smaller than __________ nm in diameter.
c) The process of separating coloured components of a mixture based on their different affinities towards stationary and mobile phases is called __________.
d) A solution that cannot dissolve any more solute at a given temperature is called a __________ solution.
e) The phenomenon responsible for the visibility of a beam of light in a colloidal solution is known as the __________ effect.
f) Brass is an alloy of copper and __________.
g) The method used to obtain pure copper sulphate crystals from its solution is __________.
h) A substance that changes directly from solid state to vapour state on heating is said to undergo __________.
i) The dispersed phase and the dispersion medium in milk are __________ and water respectively.
j) The particles of a suspension can be separated from the liquid by __________.
k) A pure substance has a __________ composition throughout.
l) Air is considered a __________ mixture because its composition may vary from place to place.
m) The process of settling down of heavier insoluble particles in a liquid is called __________.
n) The separation of cream from milk is based on the principle of __________.
o) In crystallisation, impurities remain dissolved in the __________ liquor.
p) A colloidal solution is actually a __________ mixture, although it may appear homogeneous.
q) The method used for separating two miscible liquids having different boiling points is __________.
r) The particles of a true solution neither settle down nor can they be separated by __________.
s) Bronze is an alloy mainly composed of copper and __________.
t) Elements and compounds are collectively known as __________ substances.
a) alloy
b) 1
c) chromatography
d) saturated
e) Tyndall
f) zinc
g) crystallisation
h) sublimation
i) fat
j) filtration
k) fixed
l) homogeneous
m) sedimentation
n) centrifugation
o) mother
p) heterogeneous
q) Fractional distillation
r) filtration
s) tin
t) pure
Directions:
Choose the correct option:
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.
Q 17. Assertion (A): Distilled water and oxygen are both pure substances despite existing in different states.
Reason (R): Purity depends on the number and type of particles present, not on the physical state of matter.
A. Both A and R are true, and R is the correct explanation of A.
Q 18. Assertion (A): A colloidal solution may appear homogeneous to the naked eye but is actually heterogeneous.
Reason (R): Colloidal particles are uniformly distributed and are large enough to scatter light.
A. Both A and R are true, and R is the correct explanation of A.
Q 19. Assertion (A): A saturated solution at a given temperature can become unsaturated without adding more solvent.
Reason (R): Solubility of most solids increases with increase in temperature.
A. Both A and R are true, and R is the correct explanation of A.
Q 20. Assertion (A): Crystallisation is preferred over evaporation for obtaining pure copper sulphate crystals.
Reason (R): During evaporation, soluble impurities may remain mixed with the solid residue.
A. Both A and R are true, and R is the correct explanation of A.
Q 21. Assertion (A): A mixture of common salt and ammonium chloride can be completely separated without using water.
Reason (R): Ammonium chloride sublimes on heating while common salt does not.
A. Both A and R are true, and R is the correct explanation of A.
Q 22. What is the Tyndall effect?
The scattering of light by colloidal particles is called the Tyndall effect.
It makes the path of light visible in a colloidal solution.
Example: Sunlight passing through fog.
Q 23. Define colloid and give two examples.
A colloid is a heterogeneous mixture in which very small particles are uniformly spread throughout another substance.
Examples:
1. Milk
2. Fog
Q 24. Explain the process of sublimation with one example.
Sublimation is the process in which a solid changes directly into vapour without changing into liquid on heating.
Example: Ammonium chloride changes directly into vapour on heating.
Q 25. What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 150 grams of water at 313 K if its solubility is 62g at 313K.
Solubility of potassium nitrate = 62 g in 100 g water at 313 K.
For 150 g water: 62/100 x 150 = 93 g
93 g of potassium nitrate is needed.
Q 26. How would you prepare 500 mL of a 70% volume by volume aqueous solution of acetone?
70% (v/v) means 70 mL solute in 100 mL solution.
For 500 mL solution:
70/100 x 500 = 350mL
Take 350 mL acetone and add water to make the total volume 500 mL.
Q 27. 36g of common salt is dissolved in 100 g of water at 396K to make a saturated solution. Find the concentration (mass by mass) of the solution at this temperature.
Mass of solute = 36 g
Mass of water = 100 g
Mass of solution = 136 g
Mass % = 36/136 x 100
= 26.47%
Answer: Concentration = 26.47% (mass by mass)
Q 28. What mass of potassium chloride would be needed to form a saturated solution in 50 g of water at 313 K? (Given solubility of salt at 313 K is 40 g)
Solubility = 40 g in 100 g water
For 50 g water:
40/100 x 50 = 20g
Answer: 20 g potassium chloride is needed.
Q 29. What is a solution? Explain the properties of a true solution with examples.
A solution is a homogeneous mixture of two or more substances.
Properties:
1. Particles are very small.
2. Particles cannot be seen with naked eyes.
3. They do not scatter light.
4. Particles do not settle down.
Example: Salt solution.
Q 30. Explain the process of evaporation, condensation and distillation with examples.
Evaporation:
Conversion of liquid into vapour at any temperature below boiling point.
Example: Drying of clothes.
Condensation:
Conversion of vapour into liquid on cooling.
Example: Formation of water droplets on a cold glass.
Distillation:
Method used to separate liquids based on different boiling points.
Example: Separation of alcohol and water.
Q 31. What is centrifugation? Explain its working and applications in daily life.
Centrifugation is a method used to separate lighter and heavier particles by spinning rapidly.
Working:
When rotated at high speed, heavier particles settle down while lighter particles remain above.
Applications:
1. Separation of cream from milk.
2. Used in washing machines to dry clothes.
Q 32. Describe the process of chromatography. How is it useful in separating coloured substances?
Chromatography is a technique used to separate coloured substances based on different rates of movement through a stationary medium.
Process:
1. A spot of ink is placed on filter paper.
2. The paper is dipped in a solvent.
3. The solvent rises upward carrying colours.
4. Different colours move at different speeds and get separated.
Uses:
- Separating colours in ink.
- Identifying dyes and pigments.
Q 33. Explain sublimation with a labelled diagram and suitable examples.
Sublimation is the process in which a solid changes directly into vapour on heating and vapour changes back to solid on cooling.
Examples:
- Ammonium chloride
- Camphor
- Naphthalene balls
Q 34. Explain the physical and chemical properties of metals and non-metals with examples.
Metals
Physical Properties:
1. Lustrous
2. Malleable
3. Ductile
4. Good conductors of heat and electricity
Example: Copper, iron
Chemical Properties:
1. React with oxygen to form basic oxides.
2. React with acids to produce hydrogen gas.
Non-metals
Physical Properties:
1. Dull
2. Brittle
3. Poor conductors
Example: Sulphur, phosphorus
Chemical Properties:
1. Form acidic oxides.
2. Usually do not react with acids.
Q 35. Distinguish between a solution and a colloid on the basis of:
- Particle size
- Visibility of particles
- Tyndall effect
- Stability
Give one example of each.
| Basis | Solution | Colloid |
|---|---|---|
| Particle size | Less than 1 nm | Between 1 nm and 1000 nm |
| Visibility | Not visible | Not visible to naked eye |
| Tyndall effect | Does not show | Shows |
| Stability | Stable | Stable |
Examples:
- Solution: Salt solution
- Colloid: Milk
Q 36. A student claims that milk is a pure substance because it appears uniform throughout. Do you agree? Give three reasons to justify your answer.
No, I do not agree that milk is a pure substance.
Reasons:
1. Milk is a colloid, not a pure substance.
2. It contains water, fat, proteins and minerals mixed together.
3. It shows the Tyndall effect, proving it is a heterogeneous mixture.
Q 37. A student mixes water and alcohol and then separates them again.
1. Which method of separation should be used?
2. What property is used in this method?
3. Why is filtration not suitable?
a) Distillation
b) Difference in boiling points of water and alcohol.
c) Because both are liquids and completely mix with each other.
Q 38. A chemist obtains colourless crystals from a blue solution through crystallisation. Another student claims:
“The crystals should also be blue because they came from a blue solution.”
Is the statement always correct? Justify your answer with scientific reasoning.
No, the statement is not always correct.
During crystallisation, only the pure substance forms crystals while impurities remain dissolved in the mother liquor.
If the blue colour is due to impurities, the crystals may become colourless after purification.
Thus, colour of crystals depends on the substance obtained.
Q 39. A dairy farmer wants to separate cream from milk.
a) Which method is used?
b) Explain the principle behind it.
c) Why is filtration not suitable?
a) Centrifugation
b) Heavier particles move outward while lighter cream separates due to rapid spinning.
c) Because cream particles are too small and pass through filter paper.
Q 40. Two colourless liquids A and B are mixed together.
- Liquid A boils at 78°C.
- Liquid B boils at 100°C.
a) Which method would you use to separate them?
b) Explain why this method works.
c) What would happen if both liquids had nearly the same boiling point?
a) Distillation
b) Because liquids A and B have different boiling points (78°C and 100°C).
Liquid A boils first and gets separated.
c) Separation would become difficult and fractional distillation would be required.