📘 CBSE Class 9 Science – Matter in Our Surroundings

📝 Part 2: MCQs (Q26–Q50)

Q26. Which of the following has highest density?

A) Solids
B) Liquids
C) Gases
D) Plasma

✅ Answer: A) Solids

• A) Correct: Molecules are tightly packed → highest density.
• B) Incorrect: Liquids have less density than solids (exceptions: ice vs water).
• C) Incorrect: Gases are least dense.
• D) Incorrect: Plasma is similar to gases.

Q27. Which factor increases the rate of diffusion in gases?

A) Lower temperature
B) Higher temperature
C) Decrease in kinetic energy
D) Decrease in molecular motion

✅ Answer: B) Higher temperature

• A) Incorrect: Lower temperature slows diffusion.
• B) Correct: Higher temperature → faster particle motion → faster diffusion.
• C) Incorrect: Lower kinetic energy reduces diffusion.
• D) Incorrect: Decreased motion reduces diffusion.

Q28. Which of the following is a chemical change?

A) Melting of ice
B) Boiling of water
C) Burning of candle
D) Evaporation of water

✅ Answer: C) Burning of candle

• A) Incorrect: Physical change.
• B) Incorrect: Physical change.
• C) Correct: Burning involves new substances formed (CO₂, water vapor).
• D) Incorrect: Physical change.

Q29. Latent heat of vaporization of water is approximately:

A) 22 J/g
B) 80 J/g
C) 540 J/g
D) 1000 J/g

✅ Answer: C) 540 J/g

• A) Incorrect: Too low.
• B) Incorrect: 80 J/g is latent heat of fusion of ice.
• C) Correct: Water requires 540 J/g to vaporize.
• D) Incorrect: Too high.

Q30. The interconversion of states of matter is brought about by:

A) Temperature and pressure
B) Density and volume
C) Weight and shape
D) Color and hardness

✅ Answer: A) Temperature and pressure

• A) Correct: Heating, cooling, and changing pressure → state changes.
• B) Incorrect: Density and volume are consequences, not causes.
• C) Incorrect: Weight/shape do not cause state change.
• D) Incorrect: Color/hardness are properties.

Q31. Which of the following has neither definite shape nor definite volume?

A) Solid
B) Liquid
C) Gas
D) None of these

✅ Answer: C) Gas

• A) Incorrect: Solids have fixed shape and volume.
• B) Incorrect: Liquids have definite volume, not shape.
• C) Correct: Gases have neither definite shape nor volume.
• D) Incorrect: Not true.

Q32. At what temperature does Kelvin scale start?

A) –100°C
B) –273°C
C) 0°C
D) 100°C

✅ Answer: B) –273°C

• A) Incorrect: Not the absolute zero.
• B) Correct: –273°C = 0 K (absolute zero).
• C) Incorrect: 0°C = freezing point of water.
• D) Incorrect: 100°C = boiling point.

Q33. Which of the following is NOT a characteristic of matter particles?

A) They occupy space
B) They have mass
C) They are continuously moving
D) They cannot be divided further

✅ Answer: D) They cannot be divided further

• A) Incorrect: True property.
• B) Incorrect: True property.
• C) Incorrect: True property (Brownian motion).
• D) Correct: Atoms can be divided into subatomic particles.

Q34. The SI unit of density is:

A) g/cm³
B) kg/m³
C) N/m²
D) J/kg

✅ Answer: B) kg/m³

• A) Incorrect: g/cm³ is commonly used but not SI.
• B) Correct: SI unit is kg/m³.
• C) Incorrect: N/m² = Pascal (pressure).
• D) Incorrect: J/kg = specific energy.

Q35. Which of the following is used to measure temperature precisely in labs?

A) Thermometer
B) Barometer
C) Hygrometer
D) Manometer

✅ Answer: A) Thermometer

• A) Correct: Thermometer measures temperature.
• B) Incorrect: Barometer measures pressure.
• C) Incorrect: Hygrometer measures humidity.
• D) Incorrect: Manometer measures pressure of gas.

Q36. Which one is NOT a pure substance?

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

✅ Answer: C) Air

• A) Incorrect: Oxygen = element.
• B) Incorrect: Water = compound.
• C) Correct: Air is a mixture, not pure.
• D) Incorrect: Gold is pure element.

Q37. Which phenomenon is responsible for spreading smell of perfume?

A) Osmosis
B) Diffusion
C) Conduction
D) Evaporation

✅ Answer: B) Diffusion

• A) Incorrect: Osmosis occurs in liquids with membranes.
• B) Correct: Perfume particles spread via diffusion.
• C) Incorrect: Conduction = heat transfer.
• D) Incorrect: Evaporation happens first, but spreading = diffusion.

Q38. Which condition favors liquefaction of gases?

A) High temperature, low pressure
B) Low temperature, high pressure
C) Low temperature, low pressure
D) High temperature, high pressure

✅ Answer: B) Low temperature, high pressure

• A) Incorrect: Opposite effect.
• B) Correct: Cooling + compression → gas becomes liquid.
• C) Incorrect: Low pressure prevents liquefaction.
• D) Incorrect: High temperature resists liquefaction.

Q39. Which statement about plasma is TRUE?

A) It is a form of solid
B) It consists of ions and electrons
C) It has fixed shape and volume
D) It does not conduct electricity

✅ Answer: B) It consists of ions and electrons

• A) Incorrect: Plasma is not solid.
• B) Correct: Plasma = ionized gas of charged particles.
• C) Incorrect: It has no fixed shape/volume.
• D) Incorrect: Plasma conducts electricity.

Q40. Which of these processes is endothermic?

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

✅ Answer: C) Melting

• A) Incorrect: Condensation releases heat.
• B) Incorrect: Freezing releases heat.
• C) Correct: Melting absorbs heat (endothermic).
• D) Incorrect: Deposition releases heat.

Q41. Which gas is used in dry ice?

A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Hydrogen

✅ Answer: C) Carbon dioxide

• A) Incorrect: Oxygen not used.
• B) Incorrect: Nitrogen → liquid nitrogen, not dry ice.
• C) Correct: Solid CO₂ = dry ice.
• D) Incorrect: Hydrogen not used.

Q42. Which property increases when ice melts into water?

A) Volume
B) Density
C) Shape
D) Rigidity

✅ Answer: B) Density

• A) Incorrect: Volume decreases slightly.
• B) Correct: Density of water > ice.
• C) Incorrect: Shape is not fixed for liquids.
• D) Incorrect: Rigidity decreases.

Q43. Which factor does NOT affect boiling point of liquid?

A) Pressure
B) Temperature
C) Impurities
D) Color

✅ Answer: D) Color

• A) Incorrect: Pressure affects boiling point.
• B) Incorrect: Boiling occurs at specific temp under given conditions.
• C) Incorrect: Impurities raise boiling point.
• D) Correct: Color does not affect boiling point.

Q44. Which of these best explains why clothes dry faster on a windy day?

A) High pressure
B) Low pressure
C) Increased evaporation due to wind
D) High density

✅ Answer: C) Increased evaporation due to wind

• A) Incorrect: Pressure has little effect.
• B) Incorrect: Same reason.
• C) Correct: Wind carries away water vapour → faster evaporation.
• D) Incorrect: Density not relevant.

Q45. Which of the following has highest kinetic energy?

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

✅ Answer: D) Plasma

• A) Incorrect: Solids least kinetic energy.
• B) Incorrect: Liquids more than solids but less than gases.
• C) Incorrect: Gases high but less than plasma.
• D) Correct: Plasma = highest energy state of matter.

Q46. Which is not an example of sublimation?

A) Dry ice
B) Camphor
C) Iodine
D) Ice

✅ Answer: D) Ice

• A) Incorrect: Dry ice sublimates.
• B) Incorrect: Camphor sublimates.
• C) Incorrect: Iodine sublimates.
• D) Correct: Ice melts into liquid, not sublimes.

Q47. Which property explains the smell of food reaching us quickly from kitchen?

A) Osmosis
B) Diffusion
C) Evaporation
D) Convection

✅ Answer: B) Diffusion

• A) Incorrect: Osmosis needs membrane.
• B) Correct: Gas molecules spread by diffusion.
• C) Incorrect: Evaporation occurs but spreading = diffusion.
• D) Incorrect: Convection not main cause here.

Q48. At room temperature, the state of matter for oxygen is:

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

✅ Answer: C) Gas

• A) Incorrect: Oxygen not solid at room temperature.
• B) Incorrect: Oxygen liquefies at very low temp.
• C) Correct: Exists as gas at room temp.
• D) Incorrect: Plasma only at very high temp.

Q49. Which of these best defines diffusion?

A) Movement of solvent through membrane
B) Spreading of particles from high to low concentration
C) Flow of liquid upwards in plants
D) Conversion of liquid into vapour

✅ Answer: B) Spreading of particles from high to low concentration

• A) Incorrect: That’s osmosis.
• B) Correct: Definition of diffusion.
• C) Incorrect: That’s transpiration pull.
• D) Incorrect: Evaporation, not diffusion.

Q50. Which of these substances shows anomalous expansion on freezing?

A) Alcohol
B) Kerosene
C) Water
D) Mercury

✅ Answer: C) Water

• A) Incorrect: Alcohol does not.
• B) Incorrect: Kerosene does not.
• C) Correct: Water expands on freezing, hence ice floats.
• D) Incorrect: Mercury contracts normally.

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