Chapter 11 MCQs

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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1

Which row correctly describes the particles in a solid?

	arrangement	motion
A	far apart and random	move freely in all directions
B	close together and regular	vibrate about fixed positions
C	close together and random	move freely past each other
D	far apart and regular	vibrate about fixed positions

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2

Which row correctly describes the particles in a liquid?

	arrangement	motion
A	close together and random	move past each other
B	far apart and random	move freely at high speed
C	close together and regular	vibrate only in fixed positions
D	far apart and regular	move past each other

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3

Which row correctly describes the particles in a gas?

	arrangement	motion
A	close together	vibrate about fixed positions
B	close together	move past each other slowly
C	far apart	move randomly and rapidly
D	far apart	remain in fixed positions

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4

A substance has a fixed volume but no fixed shape.

Which state is it most likely to be in?

A solid
B liquid
C gas
D plasma

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5

A substance has no fixed shape and no fixed volume.

Which particle description best explains this?

A particles are held in fixed positions
B particles are close and only vibrate
C particles are far apart and move randomly
D particles are arranged in a regular lattice

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6

A solid is heated but does not melt.

Which statement about its particles is correct?

A They stop vibrating.
B They vibrate with greater average kinetic energy.
C They move much farther apart and fill the container.
D They become arranged randomly and flow.

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7

A liquid is heated but does not boil.

Which statement is correct?

A The particles move faster on average.
B The particles become fixed in position.
C The particles lose kinetic energy.
D The forces between particles become zero.

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8

A gas is heated in a sealed rigid container.

Which statement best explains the increase in gas pressure?

A Particles expand and occupy more space.
B Particles collide with the walls more often and with greater force.
C The number of particles increases.
D The container walls become thinner.

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9

A fixed mass of gas is kept at constant temperature. Its volume is reduced from 600 cm³ to 200 cm³. Its initial pressure is 90 kPa.

What is the final pressure?

A 30 kPa
B 90 kPa
C 270 kPa
D 540 kPa

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10

A gas has pressure 120 kPa and volume 250 cm³. The temperature is constant. The pressure is increased to 300 kPa.

What is the new volume?

A 50 cm³
B 100 cm³
C 625 cm³
D 900 cm³

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For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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11

A fixed mass of gas at constant temperature obeys pV = constant.

Which graph best represents pressure against volume?

A a straight line through the origin with positive gradient
B a horizontal straight line
C a curve decreasing as volume increases
D a vertical straight line

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12

For a fixed mass of gas at constant temperature, pressure is plotted against 1/volume.

What graph is expected?

A horizontal line
B straight line through the origin
C curve decreasing from left to right
D vertical line

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13

A fixed mass of gas at constant temperature has pressure 1.5 × 10⁵ Pa and volume 4.0 × 10⁻³ m³.

What is the value of pV?

A 37.5 J
B 60 J
C 375 J
D 600 J

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14

A gas in a syringe has volume 80 cm³ and pressure 100 kPa. The syringe is slowly compressed to 50 cm³ at constant temperature.

What is the final pressure?

A 62.5 kPa
B 100 kPa
C 160 kPa
D 250 kPa

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15

A student compresses a gas quickly in a syringe. The temperature rises during compression.

The student uses p₁V₁ = p₂V₂ to calculate the final pressure.

Why may the calculated value be inaccurate?

A The gas mass is fixed.
B The temperature is not constant.
C The volume decreases.
D The pressure increases.

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16

A gas at constant temperature is compressed to half its original volume.

What happens to its pressure?

A it becomes one quarter
B it halves
C it doubles
D it becomes four times larger

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17

A gas at constant temperature has its volume increased by a factor of 4.

What happens to its pressure?

A it becomes one quarter
B it halves
C it doubles
D it becomes four times larger

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18

A gas bubble rises through water. The water pressure around it decreases as it rises. Assume the temperature remains constant.

What happens to the volume of the bubble?

A it decreases because pressure decreases
B it increases because pressure decreases
C it remains the same because mass is fixed
D it becomes zero at the surface

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19

A fixed mass of gas at constant temperature has its volume changed from 2.0 × 10⁻⁴ m³ to 8.0 × 10⁻⁴ m³. Its initial pressure is 400 kPa.

What is the final pressure?

A 25 kPa
B 100 kPa
C 1600 kPa
D 3200 kPa

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20

A fixed mass of gas has pressure 75 kPa and volume 120 cm³. It is compressed at constant temperature until its pressure is 180 kPa.

What is its final volume?

A 31 cm³
B 50 cm³
C 288 cm³
D 375 cm³

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21

A gas in a sealed container exerts pressure on the walls.

What causes this pressure?

A weight of gas particles only
B collisions of gas particles with the container walls
C attraction between particles and the container walls only
D expansion of individual particles

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22

Which change reduces the pressure of a fixed mass of gas in a sealed container?

A increasing temperature at constant volume
B decreasing volume at constant temperature
C increasing volume at constant temperature
D increasing particle speed at constant volume

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23

A gas is compressed at constant temperature.

Which row correctly describes what happens to collision frequency with the walls and pressure?

	collision frequency	pressure
A	decreases	decreases
B	decreases	increases
C	increases	increases
D	increases	decreases

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24

A fixed mass of gas is cooled at constant volume.

Which statement is correct?

A particles move faster and pressure increases
B particles move slower and pressure decreases
C particles move slower and pressure increases
D particles move farther apart and pressure decreases

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25

Brownian motion is observed when smoke particles are viewed under a microscope.

What causes the random motion of the smoke particles?

A smoke particles attracting each other
B unequal collisions by air molecules
C smoke particles changing into air molecules
D convection currents only

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For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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26

What does Brownian motion provide evidence for?

A atoms in solids are arranged regularly
B gas molecules move randomly
C liquids have fixed shapes
D smoke particles have no mass

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27

Smoke particles in air are seen moving randomly. The air temperature is increased.

What happens to the random motion of the smoke particles?

A it becomes slower because air expands
B it becomes more vigorous because air molecules move faster
C it stops because air molecules become lighter
D it becomes regular and predictable

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28

A very small pollen grain is suspended in water. It moves randomly when observed under a microscope.

Which statement is correct?

A water molecules are too large to move
B the pollen grain is hit unevenly by water molecules
C the pollen grain moves because of gravity only
D water molecules collide equally on all sides at every instant

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29

A student observes Brownian motion of smoke particles. He says, “The smoke particles move because they collide with each other.”

What is the best correction?

A The smoke particles move because air molecules collide with them randomly.
B The smoke particles move because they are weightless.
C The smoke particles move because they are magnetic.
D The smoke particles move because light pushes them steadily.

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30

A gas is compressed at constant temperature. Which statement about the average kinetic energy of its particles is correct?

A it decreases
B it stays the same
C it increases
D it becomes zero

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31

A fixed mass of gas is heated at constant volume.

Which statement about the average kinetic energy of its particles is correct?

A it decreases
B it stays the same
C it increases
D it becomes independent of temperature

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32

A sealed rigid container holds a fixed mass of gas. Its absolute temperature doubles.

What happens to the gas pressure?

A it halves
B it remains unchanged
C it doubles
D it becomes four times larger

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33

A gas has a pressure of 100 kPa at 300 K in a sealed rigid container. The gas is heated to 450 K.

What is the new pressure?

A 67 kPa
B 150 kPa
C 300 kPa
D 450 kPa

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34

A fixed mass of gas in a sealed rigid container is cooled from 400 K to 250 K. Its initial pressure is 160 kPa.

What is its final pressure?

A 64 kPa
B 100 kPa
C 256 kPa
D 310 kPa

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35

A gas has pressure 200 kPa at 27°C in a sealed rigid container. It is heated to 327°C.

What is the new pressure?

A 100 kPa
B 220 kPa
C 400 kPa
D 2400 kPa

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36

Why must Celsius temperature be converted to Kelvin in gas pressure calculations involving temperature?

A Celsius temperature can be negative and is not proportional to average kinetic energy.
B Kelvin temperature has smaller units than Celsius.
C Celsius temperature measures pressure directly.
D Kelvin temperature removes the effect of gas volume.

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37

A fixed mass of gas has volume 300 cm³ at a pressure of 200 kPa. It is compressed at constant temperature until its volume is 120 cm³.

What is the final pressure?

A 80 kPa
B 300 kPa
C 500 kPa
D 720 kPa

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38

A gas at constant temperature has pressure p and volume V. Its pressure is tripled.

What is its new volume?

A V/9
B V/3
C 3V
D 9V

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39

A fixed mass of gas has pressure 90 kPa and volume 500 cm³. It expands at constant temperature until the pressure is 45 kPa.

What is its new volume?

A 250 cm³
B 500 cm³
C 1000 cm³
D 2000 cm³

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40

A gas is trapped in a cylinder by a piston. The piston moves outwards slowly while temperature remains constant.

Which row is correct?

	volume	pressure
A	increases	increases
B	increases	decreases
C	decreases	increases
D	decreases	decreases

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For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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41

A gas at constant temperature expands from 0.20 m³ to 0.50 m³. Its initial pressure is 250 kPa.

What is its final pressure?

A 40 kPa
B 100 kPa
C 625 kPa
D 1000 kPa

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42

A gas has pressure 1.0 × 10⁵ Pa and volume 6.0 × 10⁻⁴ m³. It is compressed at constant temperature to a volume of 2.0 × 10⁻⁴ m³.

What is the final pressure?

A 3.3 × 10⁴ Pa
B 1.0 × 10⁵ Pa
C 3.0 × 10⁵ Pa
D 1.2 × 10⁶ Pa

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43

Which statement about the spacing between particles is correct?

A gas particles are usually much farther apart than liquid particles
B liquid particles are usually much farther apart than gas particles
C solid particles are usually farther apart than gas particles
D all states have the same particle spacing

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44

Which statement about forces between particles is correct?

A forces between gas particles are strongest in normal conditions
B forces between particles are stronger in solids and liquids than in gases
C forces between particles do not exist in liquids
D forces between particles are identical in all states

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45

A liquid changes into a gas during boiling.

Which statement best describes the change in particle arrangement?

A particles become closer together and more regular
B particles become fixed in position
C particles become much farther apart and move freely
D particles lose all kinetic energy

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46

A gas changes into a liquid during condensation.

Which statement is correct?

A particles become farther apart
B particles become closer together and forces between them become more significant
C particles stop moving completely
D particles become arranged in a fixed lattice immediately

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47

A solid changes into a liquid during melting.

Which statement is correct?

A particles break into smaller particles
B particles become able to move past each other
C particles stop vibrating
D particles become much farther apart like a gas immediately

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48

A fixed mass of gas is compressed at constant temperature. Its volume decreases by 40%.

What happens to its pressure?

A it becomes 0.40 times the original pressure
B it becomes 0.60 times the original pressure
C it becomes 1.67 times the original pressure
D it becomes 2.50 times the original pressure

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49

A fixed mass of gas at constant temperature has its pressure increased by 25%.

What happens to its volume?

A it becomes 0.80 times the original volume
B it becomes 1.25 times the original volume
C it becomes 0.25 times the original volume
D it becomes 4.0 times the original volume

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50

A gas syringe contains 40 cm³ of air at 100 kPa. The piston is pushed in until the volume is 25 cm³. The temperature rises during compression.

Compared with the pressure calculated using p₁V₁ = p₂V₂, the actual pressure is likely to be:

A smaller because the gas is warmer
B the same because mass is unchanged
C larger because the gas is warmer
D zero because the piston moves

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For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Chapter 11 Answer Key

Q	Ans	Q	Ans	Q	Ans	Q	Ans	Q	Ans
1	B	11	C	21	B	31	C	41	B
2	A	12	B	22	C	32	C	42	C
3	C	13	D	23	C	33	B	43	A
4	B	14	C	24	B	34	B	44	B
5	C	15	B	25	B	35	C	45	C
6	B	16	C	26	B	36	A	46	B
7	A	17	A	27	B	37	C	47	B
8	B	18	B	28	B	38	B	48	C
9	C	19	B	29	A	39	C	49	A
10	B	20	B	30	B	40	B	50	C

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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Detailed Explanations

1. B

• In a solid:

  • particles are close together

  • particles are usually in a regular arrangement

  • particles vibrate about fixed positions

• They do not move freely from place to place.

2. A

• In a liquid:

  • particles are close together

  • arrangement is random

  • particles can move/slide past each other

• This is why liquids have fixed volume but no fixed shape.

3. C

• In a gas:

  • particles are far apart

  • particles move randomly and rapidly

  • forces between particles are very weak except during collisions

4. B

• Fixed volume but no fixed shape = liquid.

• A solid has fixed shape and fixed volume.

• A gas has no fixed shape and no fixed volume.

5. C

• A gas has no fixed shape and no fixed volume because its particles are far apart and move randomly.

• They spread out to fill the container.

6. B

• Heating a solid increases the average kinetic energy of its particles.

• Since it does not melt, particles still vibrate about fixed positions.

• They vibrate more strongly/faster.

7. A

• Heating a liquid increases the average kinetic energy of the particles.

• The particles move faster on average.

• The forces between particles do not become zero unless it changes fully into gas.

8. B

• Heating a gas in a sealed rigid container:

  • particles move faster

  • collisions with walls become more frequent

  • collisions are harder

• Therefore pressure increases.

9. C

• Constant temperature, fixed mass of gas:

  • p₁V₁ = p₂V₂

• 90 × 600 = p₂ × 200

• p₂ = 54 000 / 200

• p₂ = 270 kPa

10. B

• p₁V₁ = p₂V₂

• 120 × 250 = 300 × V₂

• V₂ = 30 000 / 300

• V₂ = 100 cm³

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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11. C

• For a fixed mass of gas at constant temperature:

  • pV = constant

  • p is inversely proportional to V

• So pressure decreases as volume increases.

• The graph is a decreasing curve, not a straight line through the origin.

12. B

• pV = constant

• So p = constant × 1/V

• Therefore pressure is directly proportional to 1/volume.

• A graph of p against 1/V is a straight line through the origin.

13. D

• pV = 1.5 × 10⁵ × 4.0 × 10⁻³

• pV = 6.0 × 10²

• pV = 600 J

• Pa m³ is equivalent to joules because:

  • Pa = N/m²

  • Pa m³ = N m = J

14. C

• p₁V₁ = p₂V₂

• 100 × 80 = p₂ × 50

• p₂ = 8000 / 50

• p₂ = 160 kPa

15. B

• p₁V₁ = p₂V₂ only works for a fixed mass of gas at constant temperature.

• The gas is compressed quickly and temperature rises.

• Since temperature is not constant, the calculated pressure may be inaccurate.

16. C

• At constant temperature:

  • pressure is inversely proportional to volume

• If volume halves, pressure doubles.

17. A

• At constant temperature:

  • pressure ∝ 1/volume

• If volume becomes 4 times larger, pressure becomes one quarter.

18. B

• As the bubble rises, surrounding water pressure decreases.

• At constant temperature:

  • lower pressure means larger volume.

• So the bubble expands.

19. B

• Volume increases from 2.0 × 10⁻⁴ m³ to 8.0 × 10⁻⁴ m³.

• Volume becomes 4 times larger.

• Pressure becomes 4 times smaller.

• Final pressure = 400 / 4

• Final pressure = 100 kPa

20. B

• p₁V₁ = p₂V₂

• 75 × 120 = 180 × V₂

• V₂ = 9000 / 180

• V₂ = 50 cm³

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21. B

• Gas pressure is caused by gas particles colliding with the container walls.

• Each collision exerts a tiny force.

• Huge numbers of collisions produce pressure.

22. C

• Increasing the volume at constant temperature gives particles more space.

• They collide with the walls less often.

• Pressure decreases.

23. C

• Compressing gas at constant temperature decreases volume.

• Particles travel a shorter distance before hitting the walls.

• Collision frequency increases.

• Pressure increases.

24. B

• Cooling at constant volume reduces average kinetic energy.

• Particles move slower.

• Collisions are less frequent/less forceful.

• Pressure decreases.

25. B

• Smoke particles move randomly because air molecules collide with them unevenly.

• At any instant, impacts on one side may be greater than on the other side.

• This causes random jerky motion.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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26. B

• Brownian motion provides evidence that gas molecules move randomly.

• The smoke particles are visible, but the air molecules causing the motion are too small to see directly.

27. B

• Increasing temperature increases the average kinetic energy of air molecules.

• Air molecules move faster.

• Collisions with smoke particles become more energetic.

• Brownian motion becomes more vigorous.

28. B

• The pollen grain is hit unevenly by water molecules.

• These random molecular collisions cause the pollen grain to move randomly.

• If collisions were exactly equal on all sides at every instant, there would be no random movement.

29. A

• The smoke particles do not mainly move because they collide with each other.

• They move because invisible air molecules hit them randomly.

• That is the important evidence behind Brownian motion.

30. B

• Average kinetic energy of gas particles depends on temperature.

• The gas is compressed at constant temperature.

• Therefore average kinetic energy stays the same.

• Pressure changes because the volume changes, not because particle energy changes.

31. C

• Heating a gas increases temperature.

• Higher temperature means higher average kinetic energy.

• Therefore the gas particles move faster on average.

32. C

• For a fixed mass of gas at constant volume:

  • pressure is directly proportional to absolute temperature

• If Kelvin temperature doubles, pressure doubles.

33. B

• p₁/T₁ = p₂/T₂

• p₂ = p₁ × T₂ / T₁

• p₂ = 100 × 450 / 300

• p₂ = 150 kPa

34. B

• p₁/T₁ = p₂/T₂

• p₂ = 160 × 250 / 400

• p₂ = 160 × 0.625

• p₂ = 100 kPa

35. C

• Convert Celsius to Kelvin:

  • 27°C = 300 K

  • 327°C = 600 K

• Temperature doubles.

• At constant volume, pressure doubles.

• New pressure = 200 × 2

• New pressure = 400 kPa

• The trap is using Celsius directly like 327/27. That is absolute chaos.

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36. A

• Gas pressure-temperature calculations need Kelvin because Kelvin temperature is proportional to average kinetic energy.

• Celsius can be negative and is not proportional to particle kinetic energy.

• Always convert °C to K using:

  • K = °C + 273

37. C

• p₁V₁ = p₂V₂

• 200 × 300 = p₂ × 120

• p₂ = 60 000 / 120

• p₂ = 500 kPa

38. B

• Constant temperature:

  • pV = constant

• If pressure is tripled, volume becomes one third.

• New volume = V/3

39. C

• Pressure decreases from 90 kPa to 45 kPa.

• Pressure halves.

• At constant temperature, volume doubles.

• New volume = 500 × 2

• New volume = 1000 cm³

40. B

• Piston moves outwards:

  • volume increases

• Temperature constant:

  • pressure decreases

• Therefore volume increases and pressure decreases.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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41. B

• p₁V₁ = p₂V₂

• 250 × 0.20 = p₂ × 0.50

• p₂ = 50 / 0.50

• p₂ = 100 kPa

42. C

• p₁V₁ = p₂V₂

• 1.0 × 10⁵ × 6.0 × 10⁻⁴ = p₂ × 2.0 × 10⁻⁴

• p₂ = (1.0 × 10⁵ × 6.0) / 2.0

• p₂ = 3.0 × 10⁵ Pa

43. A

• Gas particles are usually much farther apart than liquid particles.

• Solid and liquid particles are usually close together.

• Gas particles have large spaces between them.

44. B

• Forces between particles are strongest/significant in solids and liquids.

• In gases under normal conditions, forces between particles are very weak except during collisions.

• Liquids still have intermolecular forces; that is why they keep a fixed volume.

45. C

• During boiling, liquid changes into gas.

• Particles become much farther apart.

• They move freely and randomly.

• They are no longer close together like in a liquid.

46. B

• During condensation, gas changes into liquid.

• Particles become closer together.

• Forces between particles become more significant.

• Particles do not stop moving completely.

47. B

• During melting:

  • particles are no longer fixed in position

  • they can move past each other

• They do not break into smaller particles.

• They do not become far apart like a gas immediately.

48. C

• Volume decreases by 40%.

• Final volume = 60% of original = 0.60V

• pV = constant

• New pressure = p / 0.60

• New pressure = 1.67 times original pressure

49. A

• Pressure increases by 25%.

• New pressure = 1.25p

• At constant temperature:

  • volume becomes 1 / 1.25 of original

• New volume = 0.80V

• So volume becomes 0.80 times the original volume

50. C

• If temperature stayed constant:

  • p₁V₁ = p₂V₂ would calculate the pressure.

• But the temperature rises during compression.

• Higher temperature increases pressure further.

• So the actual pressure is larger than the isothermal value.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

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Common Traps From This Chapter

Trap	Correct Rule
Solid particles	close, regular, vibrate about fixed positions
Liquid particles	close, random, move past each other
Gas particles	far apart, random rapid motion
Fixed volume but no fixed shape	liquid
No fixed volume or shape	gas
Heating particles	increases average kinetic energy
Gas pressure	collisions with container walls
Constant temperature gas law	p₁V₁ = p₂V₂
Pressure vs volume graph	decreasing curve
Pressure vs 1/volume graph	straight line through origin
Constant temperature	average kinetic energy unchanged
Compressing gas at constant temperature	pressure increases
Expanding gas at constant temperature	pressure decreases
Fixed volume gas	pressure proportional to Kelvin temperature
Celsius in gas calculations	convert to Kelvin
Brownian motion cause	random unequal molecular collisions
Brownian motion evidence	molecules move randomly
Gas bubble rising	pressure decreases, volume increases
Condensation	particles closer, stronger forces
Melting	particles can move past each other
Boiling	particles much farther apart
Temperature rises during compression	actual pressure greater than pV-only calculation