P3 The particle Model and Motion in Gasses (page 191)

Question 1

What is ‘All Matter’ made up of?

Answer 1

Particles

Question 2

In particle theory, you can think of the particles that make up matter as what?

Answer 2

tiny balls.

Question 3

How can you explain the ways that matter behaves in terms of how these tiny balls move, and the forces between them?

Answer 3

The three states of matter

Question 4

What are the Three States of Matter?

Answer 4

Solid (e.g. ice)
lquid (e.g. water)
gas (e.g. water vapour)

Question 5

The particles of a substance in each state are the same (solids, liquids gases), apart from what is different?

Answer 5

The arrangement and energy of the particles are different.

Question 6

What are Solids Matter?

Answer 6

Strong forces of attraction hold the particles close together in a fixed, regular arrangemtn, The particles dont have much energy so they can only vibrate about their fixed positions.

Question 7

What are Liquid Matter?

Answer 7

There are weaker forces of atraction between the partiles. The particles are close together, but can move past each other, and form irregular arrangemtns. They have more energy than the particles in a solid - they move in random directions at low speeds.

Question 8

What are Gases Matter?

Answer 8

There are almost no forces of attraction between the particles. The particles have more energy than in liquids and solids - they’re free to move, and are constantly moving with random directions and speeds.

Question 9

What is Colliding Gas Particles?

Answer 9

They create Pressure.

Question 10

Particles in gases (and liquids to a certain extent) are free to move around, what happens when the move around?

Answer 10

As they move they bang into each other and whatever else happens to get in the way (like the sides of the container they’re being kept in).

Question 11

When Particles colide with something, what happens?

Answer 11

they exert a force on it.

Pressure is the force exerted per unit area.

Question 12

In a sealed container, what unit areai s exerted by all of the particles?

Answer 12

the outward gas pressure is the total force exerted by all of the particles in the gas on a unit area of the conainter walls.

Question 13

If you increase the temperature of a gas what happens?

Answer 13

you transfer energy into the kinetic energy stores of its particles (there is more about this on p. 193)

Increasing the temperature of a gas can increase its pressure.

Question 14

The temperature of a gas is related to the average energy in what energy stores?

Answer 14

in the kinetic energy stores of the particles in the gas.

The higher the temperature, the higher the average energy.

Question 15

As you increase the temerature of a gas, the average speed of its particles increases why?

Answer 15

because the energy in the particles’ kinetic energy store is ½mv² - see page 168.

Question 16

This means that for a gas at a constant volume, increasing its temperature increases its pressure, explain what this means?

Answer 16

As the particles are travelling quicker, it means that they hit the sides of the container more often in a given amount of time.

Each particle also has a larger momentum (p.216) which means that they exert a larger force when they collide with the container.

These factors both increase the total force exerted on a unit area and so increase the pressure.

Question 17

Explain why decreasing the temperature of a fixed volume of gas decreases its pressure? (3 marks)

Answer 17

`Decreasing the temperature of the gas means that the gas particles have less energy in their kinetic energy stores (1 mark). They collide with the container less often (1 mark), and exert a smaller force when they do collide, meaning that the gas pressure is lower (1 mark).