📘 CBSE Class 9 Science – Matter in Our Surroundings

📝 Part 4: MCQs (Q76–Q100)

Q76. Which of these is NOT an example of matter?

A) Water
B) Air
C) Sound
D) Stone

✅ Answer: C) Sound

• A) Incorrect: Water has mass & volume.
• B) Incorrect: Air occupies space.
• C) Correct: Sound is a form of energy, not matter.
• D) Incorrect: Stone is solid matter.

Q77. Which of the following processes does NOT require heat absorption?

A) Evaporation
B) Melting
C) Freezing
D) Sublimation

✅ Answer: C) Freezing

• A) Incorrect: Evaporation absorbs heat.
• B) Incorrect: Melting absorbs heat.
• C) Correct: Freezing releases heat.
• D) Incorrect: Sublimation absorbs heat.

Q78. Which factor reduces the rate of evaporation?

A) Increase in temperature
B) Increase in humidity
C) Increase in surface area
D) Increase in wind speed

✅ Answer: B) Increase in humidity

• A) Incorrect: High temperature speeds evaporation.
• B) Correct: High humidity slows evaporation.
• C) Incorrect: Larger surface area increases evaporation.
• D) Incorrect: Wind helps evaporation.

Q79. Which is the correct order of density (highest to lowest)?

A) Solid > Liquid > Gas
B) Gas > Liquid > Solid
C) Liquid > Solid > Gas
D) Solid > Gas > Liquid

✅ Answer: A) Solid > Liquid > Gas

• A) Correct: Density is maximum in solids, least in gases.
• B–D) Incorrect: Wrong arrangements.

Q80. Which phenomenon is responsible for cooling in a desert cooler?

A) Condensation
B) Evaporation
C) Fusion
D) Freezing

✅ Answer: B) Evaporation

• A) Incorrect: Not condensation.
• B) Correct: Water evaporation absorbs heat, cooling the air.
• C, D) Incorrect: Not applicable.

Q81. At 1 atm pressure, the freezing point of water is:

A) 0°C
B) 32°C
C) 100°C
D) –273°C

✅ Answer: A) 0°C

• A) Correct: Water freezes at 0°C.
• B) Incorrect: 32°F (not °C).
• C) Incorrect: 100°C = boiling point.
• D) Incorrect: –273°C = absolute zero.

Q82. Which of the following explains why naphthalene balls disappear in air?

A) Evaporation
B) Fusion
C) Sublimation
D) Condensation

✅ Answer: C) Sublimation

• A) Incorrect: Evaporation applies to liquids.
• B) Incorrect: Fusion = melting.
• C) Correct: Solid → gas.
• D) Incorrect: Gas → liquid.

Q83. Which of these is NOT a characteristic of liquids?

A) Definite volume
B) Definite shape
C) Can flow
D) Less compressible than gases

✅ Answer: B) Definite shape

• A) Incorrect: Liquids have definite volume.
• B) Correct: Liquids do not have definite shape.
• C, D) Incorrect: True for liquids.

Q84. Why does ice float on water?

A) Because ice is lighter than water
B) Because of bubbles
C) Because water is denser than ice
D) Both A and C

✅ Answer: D) Both A and C

• A) Correct: Ice density < water density.
• B) Incorrect: Bubbles not the reason.
• C) Correct: Water has higher density.
• D) Correct: Both reasons together.

Q85. Which energy increases during heating of a substance without rise in temperature?

A) Potential energy
B) Kinetic energy
C) Mechanical energy
D) Nuclear energy

✅ Answer: A) Potential energy

• A) Correct: Heat absorbed increases potential energy (overcoming forces).
• B) Incorrect: Temperature rise = kinetic energy.
• C, D) Incorrect: Not relevant.

Q86. Which is the reverse process of sublimation?

A) Melting
B) Deposition
C) Condensation
D) Freezing

✅ Answer: B) Deposition

• A) Incorrect: Melting = solid → liquid.
• B) Correct: Deposition = gas → solid.
• C, D) Incorrect: Other phase changes.

Q87. Which of these is a supercooled liquid?

A) Ice
B) Glass
C) Mercury
D) Alcohol

✅ Answer: B) Glass

• A) Incorrect: Ice is crystalline solid.
• B) Correct: Glass is amorphous supercooled liquid.
• C, D) Incorrect: Not supercooled liquids.

Q88. At higher altitudes, water boils at:

A) Higher temperature
B) Lower temperature
C) Same temperature
D) Not at all

✅ Answer: B) Lower temperature

• A) Incorrect: Pressure is lower, so boiling point drops.
• B) Correct: Lower atmospheric pressure → lower boiling point.
• C) Incorrect: Not same.
• D) Incorrect: Water always boils.

Q89. Which is NOT an example of physical change?

A) Melting of ice
B) Dissolving salt in water
C) Burning of paper
D) Boiling of water

✅ Answer: C) Burning of paper

• A, B, D) Incorrect: All physical changes.
• C) Correct: Burning forms new substances → chemical.

Q90. The SI unit of latent heat is:

A) J
B) J/kg
C) Calorie
D) Erg

✅ Answer: B) J/kg

• A) Incorrect: Joule = unit of energy.
• B) Correct: Latent heat = energy per unit mass.
• C, D) Incorrect: Non-SI units.

Q91. Which of these occurs at constant temperature?

A) Heating of water from 20°C to 30°C
B) Melting of ice
C) Heating of steam
D) Heating of metal rod

✅ Answer: B) Melting of ice

• A, C, D) Incorrect: Temperature rises.
• B) Correct: During phase change, temp remains constant.

Q92. Which of the following is a crystalline solid?

A) Glass
B) Plastic
C) Ice
D) Rubber

✅ Answer: C) Ice

• A, B, D) Incorrect: Amorphous solids.
• C) Correct: Ice has regular crystal lattice.

Q93. The cooling caused by desert coolers is more effective in:

A) Rainy season
B) Winter
C) Humid weather
D) Dry weather

✅ Answer: D) Dry weather

• A, C) Incorrect: Humidity slows evaporation.
• B) Incorrect: Works but less needed.
• D) Correct: Dry air → fast evaporation → more cooling.

Q94. Which of the following is NOT a property of gases?

A) Easily compressible
B) No fixed shape
C) No fixed volume
D) High density

✅ Answer: D) High density

• A, B, C) Incorrect: True properties.
• D) Correct: Gases are low density.

Q95. The SI unit of temperature is:

A) Celsius
B) Kelvin
C) Fahrenheit
D) Degree

✅ Answer: B) Kelvin

• A, C, D) Incorrect: Non-SI units.
• B) Correct: Kelvin is SI unit.

Q96. Which change occurs when butter is melted?

A) Chemical change
B) Physical change
C) Nuclear change
D) Irreversible change

✅ Answer: B) Physical change

• A) Incorrect: No new substance formed.
• B) Correct: Only state changes.
• C, D) Incorrect: Not applicable.

Q97. The diffusion of gases is faster because:

A) Molecules are light and move fast
B) Gases are heavy
C) Gases have high density
D) Gases have fixed volume

✅ Answer: A) Molecules are light and move fast

• A) Correct: Small size and high kinetic energy → fast diffusion.
• B, C, D) Incorrect: Not true for gases.

Q98. Which is NOT an amorphous solid?

A) Glass
B) Rubber
C) Plastic
D) Diamond

✅ Answer: D) Diamond

• A, B, C) Incorrect: All amorphous.
• D) Correct: Diamond is crystalline.

Q99. Which of these explains Brownian motion?

A) Random motion of particles
B) Fixed motion of molecules
C) Movement only in solids
D) No movement at all

✅ Answer: A) Random motion of particles

• A) Correct: Brownian motion = zig-zag random motion.
• B–D) Incorrect: Not true.

Q100. Which process is used in making ice-cream without freezer (using ice + salt)?

A) Increase in boiling point
B) Decrease in freezing point
C) Evaporation
D) Condensation

✅ Answer: B) Decrease in freezing point

• A) Incorrect: Not boiling.
• B) Correct: Salt lowers freezing point → ice-cream freezes.
• C, D) Incorrect: Not the cause here.

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