particle model and pressure (topic 3)

Question 1

describe the motion of particles in a gas (2)

Answer 1

• random motion (or moving in different directions)
• range of speeds

Question 2

Answer 2

smoke particles are hit by air molecules

Question 3

Answer 3

Question 4

calculate the pressure of the air in the tyre after one stroke of the pump. Give your answer to the nearest whole number in kPa

Answer 4

Question 5

• the student needs to pump the tyre to 431 kPa
• calculate how many strokes of the pump are required to raise the pressure from 101 kPa to 431 kPa
• you may assume the pressure increase per stroke remains constant
• pressure of the air in the tyre after one stroke of the pump = 123

Answer 5

Question 6

Answer 6

Question 7

explain how particles in a gas exert a pressure on the walls of the container (3)

Answer 7

• idea of (continuous) random motion
• particles collide (hit) the walls of container
• force is produced on the container wall by gas particle
• pressure = force ÷ area

Question 8

(4)

Answer 8

• record initial pressure and volume
• turn on pump and increase the pressure by set increment
• record new pressure and volume
• repeat until desired number of measurements is reached (min 8)
• repeat experiment and average results

Question 9

describe the relationship shown by the graph (2)

Answer 9

Question 10

calculate the constant for the pressure of 161 kPa, give your answer to 2 significant figures in standard form

Answer 10

• 161 x 22 = 3,542 = 3.5 x 10^3 (to 2 sig fig)

Question 11

explain how the temperature increase would affect the pressure exerted by the gas (3)

Answer 11

• temperature would result in an increase in pressure
• because the kinetic energy/speed of the particles is higher
• more frequent collisions of the gas particles with wall of container
• gas particles hit container walls with more force
• pressure = force ÷ area

Question 12

explain what happens to the pressure reading as the piston is inserted further into the syringe (3)

Answer 12

• pressure reading increases
• smaller volume
• more frequent collisions between the gas particles and the walls

Question 13

explain why the pressure increases when the gas is heated (3)

Answer 13

• when the gas particles hit the walls of the container, they exert a force
• greater number of collisions at a higher temperature
• greater impact speed at higher temperature

Question 14

(2)

Answer 14

• water bath to heat contents up to 100°C
• ice needed to cool the contents down to 0°C

Question 15

the piston is then locked in place so that the volume is fixed, the cylinder and piston are placed in a cold room, describe how the pressure of the gas would vary as the temperature of the gas decreases

Answer 15

• pressure of gas decreases
• as the gas is cooled, the kinetic energy of the gas particles decreases

fewer collisions with wall of cylinder

lower force exerted by gas particles due to lower speed