4.3.3.1 Particle Motion in Gases

Question 1

How are the particles of a gas arranged?

Answer 1

• very far apart
• in constant random motion

Question 2

What is the pressure of a gas due to?

Answer 2

• pressure of a gas is due to the particles colliding with the walls/surface of a container that the gas is held in
• the particles collisions exert a force which acts at right angles to the walls of the container
• the total force exerted on the container is determined by the number of collisions in a set amount of time - this net force is normal (perpendicular to) the surface of the container
• as the gas exerts a force on an area the gas exerts pressure on the sides of the container

Question 3

How can we increase the pressure of a gas?

Answer 3

can increase the pressure if we increase the number of collisions per second or the energy of each collision - can do this by increasing the temperature of a gas

Question 4

What is the temperature of a gas?

Answer 4

the temperature of a gas is related to the average kinetic energy of the particles

Question 5

What does changing the temperature of gas do?

Answer 5

changing the temperature of a gas, held at a constant volume, changes the pressure exerted by the gas as well

Question 6

How does decreasing the temperature affect gas pressure?

Answer 6

• at low temperatures particles have lower kinetic energy so move less
• there are fewer collisions per second with walls of container
• less force exerted in collisions (these are low energy collisions)
• less total force exerted in same area
• therefore, a decrease in temperature leads to decrease in pressure (as pressure is force exerted per unit area)

Question 7

How does increasing the temperature affect gas pressure?

Answer 7

• the particles are moving faster (on average) because they have more KE (on average)
• therefore the frequency of collisions increases on walls of container
• greater forces exerted by collisions - between particles and walls of container (meaning collisions are high energy)
• so total force exerted by gas on walls of container on same area increases
• force exerted per unit area increase
• pressure increases (as pressure is force exerted per unit area)

Question 8

What do gases consist of?

Answer 8

gases consist of very small particles

Question 9

How are the particles of a gas arranged?

Answer 9

• very far apart
• in constant random motion
• particles constantly collide with each other and with the walls of their container

Question 10

What is most of a gas?

Answer 10

particles hardly take up any space - most of a gas is empty space

Question 11

What happens if you increase the temperature of something?

Answer 11

if you increase the temperature of something the kinetic E of its particles increases so they move more quickly or vibrate more

Question 12

What happens if you cool down a substance?

Answer 12

kinetic E of particles decreases, particles move less

Question 13

What is absolute zero?

Answer 13

• -273 degrees C
• at absolute zero atoms have as little kinetic energy as possible

Question 14

What scale relates to absolute zero?

Answer 14

Kelvin (K)

Question 15

What has kinetic E?

Answer 15

anything that’s moving (e.g. particles) has kinetic E

Question 16

What happens if you increase the temp of a gas?

Answer 16

• if you increase the temp of a gas the particles increase in kinetic energy so as you heat up a gas the average speed of its particles increases

Question 17

What happens if you double the absolute temperature (measured in Kelvin)?

Answer 17

• you double average kinetic E as well