📘 CBSE Class 9 Science – Is Matter Around Us Pure

📝 Part 4: MCQs (Q76–Q100)

Q76. Which of these is a homogeneous mixture?

A) Brass
B) Soil
C) Milk
D) Smoke

✅ Answer: A) Brass

• A) Correct: Brass = uniform alloy of copper + zinc.
• B) Incorrect: Soil is heterogeneous.
• C) Incorrect: Milk is a colloid.
• D) Incorrect: Smoke is heterogeneous.

Q77. Which method is used to separate common salt from sea water on a large scale?

A) Sedimentation
B) Evaporation
C) Distillation
D) Filtration

✅ Answer: B) Evaporation

• A) Incorrect: Not used for dissolved salts.
• B) Correct: Sunlight evaporates water, leaving salt behind.
• C) Incorrect: Distillation is costly for large scale.
• D) Incorrect: Filtration does not work for dissolved salts.

Q78. Which of the following is a pure element?

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

✅ Answer: C) Gold

• A, B, D) Incorrect: All alloys/mixtures.
• C) Correct: Gold (Au) is an element.

Q79. Which one is NOT an example of solution?

A) Air
B) Soda water
C) Sugar solution
D) Soil

✅ Answer: D) Soil

• A, B, C) Incorrect: All are solutions.
• D) Correct: Soil is heterogeneous.

Q80. Which separation technique is best for obtaining pure water from sea water?

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

✅ Answer: C) Distillation

• A) Incorrect: Filtration cannot remove dissolved salts.
• B) Incorrect: Evaporation leaves salt but water lost.
• C) Correct: Distillation collects pure water.
• D) Incorrect: Chromatography not suitable.

Q81. An example of gas in solid is:

A) Smoke
B) Foam
C) Hydrogen in palladium
D) Soda water

✅ Answer: C) Hydrogen in palladium

• A) Incorrect: Smoke = solid in gas.
• B) Incorrect: Foam = gas in liquid.
• C) Correct: Gas dissolved in metal solid.
• D) Incorrect: Soda water = gas in liquid.

Q82. Which of these does NOT form a colloid?

A) Milk
B) Blood
C) Salt solution
D) Smoke

✅ Answer: C) Salt solution

• A, B, D) Incorrect: All colloids.
• C) Correct: True solution, not colloid.

Q83. The colloid in whipped cream is:

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

✅ Answer: A) Gas in liquid

• A) Correct: Foam = gas bubbles dispersed in liquid.
• B, C, D) Incorrect: Not correct here.

Q84. Which separation technique is based on difference in boiling points?

A) Filtration
B) Distillation
C) Sedimentation
D) Magnetic separation

✅ Answer: B) Distillation

• A, C, D) Incorrect: Do not depend on boiling points.
• B) Correct: Used to separate miscible liquids.

Q85. Which of these is a suspension?

A) Muddy water
B) Milk
C) Brass
D) Soda water

✅ Answer: A) Muddy water

• A) Correct: Large particles settle → suspension.
• B) Incorrect: Milk is a colloid.
• C) Incorrect: Brass = solid solution.
• D) Incorrect: Soda water = gas in liquid solution.

Q86. Which is NOT true for mixtures?

A) They have variable composition
B) Components retain properties
C) Separation possible by physical means
D) Properties are fixed and unique

✅ Answer: D) Properties are fixed and unique

• A, B, C) Correct for mixtures.
• D) Correct answer: Fixed properties belong to compounds.

Q87. Which method separates kerosene from water?

A) Distillation
B) Filtration
C) Separating funnel
D) Centrifugation

✅ Answer: C) Separating funnel

• A) Incorrect: Not needed.
• B) Incorrect: Both are liquids.
• C) Correct: Immiscible liquids separated by funnel.
• D) Incorrect: Not applicable.

Q88. Which of these is an alloy of iron and carbon?

A) Steel
B) Brass
C) Bronze
D) German silver

✅ Answer: A) Steel

• A) Correct: Steel = iron + carbon.
• B) Incorrect: Copper + zinc.
• C) Incorrect: Copper + tin.
• D) Incorrect: Copper + zinc + nickel.

Q89. Which of these is a homogeneous mixture?

A) Salt solution
B) Muddy water
C) Oil and water
D) Soil

✅ Answer: A) Salt solution

• A) Correct: Uniform composition.
• B, C, D) Incorrect: All heterogeneous.

Q90. Which one is NOT a pure substance?

A) Oxygen
B) Water
C) Air
D) Gold

✅ Answer: C) Air

• A, B, D) Incorrect: Pure substances.
• C) Correct: Air = mixture of gases.

Q91. Which of the following colloids is used in fire extinguishers?

A) Smoke
B) Fog
C) Foam
D) Gel

✅ Answer: C) Foam

• A, B, D) Incorrect: Not used in extinguishers.
• C) Correct: Foam blankets fire and cuts off oxygen.

Q92. The separation of dyes is based on:

A) Density difference
B) Solubility difference
C) Magnetic property
D) Boiling points

✅ Answer: B) Solubility difference

• A, C, D) Incorrect: Not applicable.
• B) Correct: Chromatography works due to different solubilities.

Q93. Which of the following is a liquid-liquid colloid (emulsion)?

A) Milk
B) Smoke
C) Foam
D) Soda water

✅ Answer: A) Milk

• A) Correct: Fat droplets in water.
• B, C, D) Incorrect: Other types of colloids.

Q94. Which technique separates immiscible liquids?

A) Chromatography
B) Separating funnel
C) Filtration
D) Distillation

✅ Answer: B) Separating funnel

• A, C, D) Incorrect: Not suitable.
• B) Correct: Used for immiscible liquids like oil + water.

Q95. The dispersed phase in butter is:

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

✅ Answer: B) Fat

• A) Incorrect: Water is dispersion medium.
• B) Correct: Butter is fat dispersed in water.
• C, D) Incorrect: Not major components.

Q96. Which is NOT a correct match?

A) Smoke – solid in gas
B) Fog – liquid in gas
C) Alloy – gas in liquid
D) Milk – liquid in liquid

✅ Answer: C) Alloy – gas in liquid

• A, B, D) Correct matches.
• C) Correct answer: Alloys are solid solutions, not gas in liquid.

Q97. Which of these is NOT a physical method of separation?

A) Magnetic separation
B) Distillation
C) Filtration
D) Electrolysis

✅ Answer: D) Electrolysis

• A, B, C) Incorrect: All are physical.
• D) Correct: Electrolysis is a chemical method.

Q98. In which type of mixture can the components be seen by naked eye?

A) True solution
B) Colloid
C) Suspension
D) Alloy

✅ Answer: C) Suspension

• A, B, D) Incorrect: Not visible.
• C) Correct: Suspension particles are large and visible.

Q99. Which of these is NOT a correct example of colloid?

A) Smoke – solid in gas
B) Gel – liquid in solid
C) Fog – solid in liquid
D) Foam – gas in liquid

✅ Answer: C) Fog – solid in liquid

• A, B, D) Correct matches.
• C) Correct answer: Fog = liquid in gas.

Q100. The process used to separate pure gases from air is:

A) Filtration
B) Fractional distillation of liquid air
C) Sedimentation
D) Centrifugation

✅ Answer: B) Fractional distillation of liquid air

• A, C, D) Incorrect: Not suitable.
• B) Correct: Air liquefied and separated by boiling points.

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