Section 5: Ideal gas molecules

Question 1

How do molecules move in gas?

Answer 1

Motion of molecules in gas are random (Brownian motion)

Question 2

What is absolute zero?

Answer 2

0 kelvin or -273 celsius

Question 3

How is kelvin related to celsius?

Answer 3

kelvin = celsius + 273

Question 4

How is kelvin temp related to the KE of molecules in gas?

Answer 4

kelvin temperature is proportional to the average KE of molecules in gas

Question 5

What apparatus is used to observe Brownian motion?

Answer 5

microscope to observe smoke cell

Question 6

Define the pressure law

Answer 6

For a fixed mass of gas at a constant volume, pressure and temp (kelvin)are directly proportional
or

for a fixed mass of gas at constant pressure, volume and temp are directly proportional

Question 7

What is the effect of temperature on the motion of parties in a gas?

Answer 7

When temp is increased, the gas particles gain KE and move faster so collisions become harder + more frequent
This means pressure also increases

Question 8

How does the motion of particles exert pressure on the walls of a container?

Answer 8

• if gas is kept at the same temp the average speed of particles stays the same
• particles are continually moving + colliding with each other within the walls of the container
• when a particles collides with a wall it exerts a small force on the wall
• if temp is increase the particles gain KE and more collisions per second means a greater force on the wall, therefor higher pressure

Question 9

What is the relationship between pressure and Kelvin temp for a fixed mass of gas at constant volume?

Answer 9

pressure is directly proportional to temp in kelvins
p1 = p2
T1 T2

P/T graph;
pressure(P) on y axis
temp(T) on x axis

Question 10

Describe an experiment to investigate the pressure law

Answer 10

• Fill a water bath with water and some ice to cool it to near 0 degrees
• Write down the temp of the water(same as air in the flask) and pressure of air as shown on the pressure gauge

-light the Bunsen burner and heat the water slowly, write down the pressure and temp at roughly every 10 degrees until the water boils

Question 11

Describe the relationship between the pressure and volume of a fixed mass of gas at constant temperature

Answer 11

p1 V1 = p2 V2

Question 12

Why is there an absolute zero temperature ?

Answer 12

The particles have no more KE to lose