📘 CBSE Class 9 Science – Is Matter Around Us Pure

📝 Part 2: MCQs (Q26–Q50)

Q26. Which of the following is a heterogeneous mixture?

A) Air
B) Brass
C) Milk
D) Salt solution

✅ Answer: C) Milk

• A) Incorrect: Air is homogeneous (unless polluted).
• B) Incorrect: Brass is a uniform alloy.
• C) Correct: Milk is a colloid, hence heterogeneous.
• D) Incorrect: Salt solution is homogeneous.

Q27. Which method separates dyes from black ink?

A) Filtration
B) Chromatography
C) Distillation
D) Centrifugation

✅ Answer: B) Chromatography

• A) Incorrect: Filtration separates insoluble solids.
• B) Correct: Chromatography separates pigments.
• C) Incorrect: Distillation separates liquids.
• D) Incorrect: Centrifugation separates solids from liquids.

Q28. Fog is an example of:

A) Solid in gas
B) Liquid in gas
C) Gas in liquid
D) Gas in solid

✅ Answer: B) Liquid in gas

• A) Incorrect: Smoke is solid in gas.
• B) Correct: Fog = tiny liquid droplets in air.
• C) Incorrect: Aerated drinks are gas in liquid.
• D) Incorrect: Hydrogen in palladium is gas in solid.

Q29. Which of the following is a compound?

A) Steel
B) Air
C) Carbon dioxide
D) Soil

✅ Answer: C) Carbon dioxide

• A) Incorrect: Steel is a mixture.
• B) Incorrect: Air is a mixture.
• C) Correct: CO₂ has fixed ratio of C and O.
• D) Incorrect: Soil is a mixture.

Q30. The particles of a colloid are:

A) Less than 1 nm
B) 1–1000 nm
C) More than 1000 nm
D) Infinite

✅ Answer: B) 1–1000 nm

• A) Incorrect: <1 nm = true solution.
• B) Correct: Colloidal particles range 1–1000 nm.
• C) Incorrect: >1000 nm = suspension.
• D) Incorrect: Infinite not valid.

Q31. Which of the following is a suspension?

A) Starch in water
B) Muddy water
C) Salt solution
D) Copper sulphate solution

✅ Answer: B) Muddy water

• A) Incorrect: Starch solution is colloid.
• B) Correct: Muddy water = suspension (settles on standing).
• C, D) Incorrect: Both are true solutions.

Q32. Which of these shows the Tyndall effect?

A) Sugar solution
B) Copper sulphate solution
C) Milk
D) Distilled water

✅ Answer: C) Milk

• A, B, D) Incorrect: True solutions/pure substances → no scattering.
• C) Correct: Milk = colloid → scatters light.

Q33. The mixture of oil and water is:

A) Miscible
B) Immiscible
C) Compound
D) Element

✅ Answer: B) Immiscible

• A) Incorrect: Miscible = liquids that mix uniformly.
• B) Correct: Oil and water don’t mix → immiscible.
• C, D) Incorrect: Not a compound/element.

Q34. Which is NOT a property of a suspension?

A) Visible particles
B) Stable and do not settle
C) Scatters light
D) Heterogeneous

✅ Answer: B) Stable and do not settle

• A) Incorrect: Suspensions have visible particles.
• B) Correct: Suspensions are unstable and settle on standing.
• C, D) Incorrect: True properties.

Q35. Ink is a:

A) Compound
B) Mixture of dyes
C) Element
D) Pure substance

✅ Answer: B) Mixture of dyes

• A, C, D) Incorrect: Not pure or elemental.
• B) Correct: Ink is a mixture of pigments and solvents.

Q36. Which separation method is used in water purification plants?

A) Evaporation
B) Filtration and chlorination
C) Chromatography
D) Centrifugation

✅ Answer: B) Filtration and chlorination

• A) Incorrect: Evaporation unsuitable.
• B) Correct: Filtration removes solids, chlorination kills germs.
• C, D) Incorrect: Not used in large-scale purification.

Q37. Which one is a heterogeneous mixture?

A) Brass
B) Air
C) Soil
D) Sugar solution

✅ Answer: C) Soil

• A, B, D) Incorrect: Homogeneous mixtures.
• C) Correct: Soil is non-uniform.

Q38. Which technique separates petroleum into useful fractions?

A) Filtration
B) Evaporation
C) Fractional distillation
D) Chromatography

✅ Answer: C) Fractional distillation

• A, B, D) Incorrect: Not suitable for petroleum.
• C) Correct: Used in refineries.

Q39. Which of these is a homogeneous mixture?

A) Soil
B) Salt solution
C) Oil and water
D) Sand and iron filings

✅ Answer: B) Salt solution

• A, C, D) Incorrect: Heterogeneous mixtures.
• B) Correct: Salt solution uniform throughout.

Q40. The solute in brass is:

A) Zinc
B) Copper
C) Tin
D) Iron

✅ Answer: A) Zinc

• A) Correct: Brass = copper (solvent) + zinc (solute).
• B) Incorrect: Copper is solvent.
• C, D) Incorrect: Not present in brass.

Q41. The continuous medium in milk is:

A) Fat
B) Water
C) Protein
D) Lactose

✅ Answer: B) Water

• A) Incorrect: Fat is dispersed phase.
• B) Correct: Water forms dispersion medium.
• C, D) Incorrect: Not the continuous phase.

Q42. Colloids can be distinguished from solutions by:

A) Color
B) Tyndall effect
C) Taste
D) Smell

✅ Answer: B) Tyndall effect

• A, C, D) Incorrect: Not reliable tests.
• B) Correct: Only colloids scatter light.

Q43. Which of the following is an example of gas in liquid?

A) Soda water
B) Smoke
C) Fog
D) Air

✅ Answer: A) Soda water

• A) Correct: CO₂ dissolved in water.
• B) Incorrect: Solid in gas.
• C) Incorrect: Liquid in gas.
• D) Incorrect: Gas in gas.

Q44. The separation of butter from curd is done by:

A) Distillation
B) Sublimation
C) Centrifugation
D) Filtration

✅ Answer: C) Centrifugation

• A, B, D) Incorrect: Not suitable here.
• C) Correct: Centrifugal force separates cream/butter.

Q45. Which one is not a compound?

A) Water
B) Ammonia
C) Milk
D) Carbon dioxide

✅ Answer: C) Milk

• A, B, D) Incorrect: All pure compounds.
• C) Correct: Milk is a mixture.

Q46. The particles of suspension are:

A) <1 nm
B) 1–1000 nm
C) >1000 nm
D) None

✅ Answer: C) >1000 nm

• A) Incorrect: True solutions.
• B) Incorrect: Colloids.
• C) Correct: Suspension particles are large (>1000 nm).
• D) Incorrect: Not applicable.

Q47. Which of these is an alloy?

A) Air
B) Brass
C) Soil
D) Sugar solution

✅ Answer: B) Brass

• A, C, D) Incorrect: Not alloys.
• B) Correct: Alloy of copper and zinc.

Q48. Which is NOT an element?

A) Iron
B) Oxygen
C) Salt
D) Gold

✅ Answer: C) Salt

• A, B, D) Incorrect: All are elements.
• C) Correct: Salt is a compound (NaCl).

Q49. Mixtures are formed by:

A) Physical methods
B) Chemical reactions
C) Both A and B
D) Nuclear reactions

✅ Answer: A) Physical methods

• A) Correct: Mixtures form by physical mixing.
• B, D) Incorrect: Compounds form by chemical/nuclear.
• C) Incorrect: Not both.

Q50. Which of the following is NOT an alloy?

A) Steel
B) Brass
C) Bronze
D) Diamond

✅ Answer: D) Diamond

• A, B, C) Incorrect: All are alloys.
• D) Correct: Diamond is pure carbon (element).

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