P3: Particle Model of Matter

Question 1

Why are solids and liquids incompressible?

Answer 1

there are no gaps between the particles in them

Question 2

What is the density of a material?

Answer 2

its mass per unit volume

Question 3

What is internal energy?

Answer 3

the total kinetic energy and potential energy of all the particles in a system and is stored by these particles

Question 4

What happens when energy is added to a system?

Answer 4

its temperature increases

Question 5

What happens when energy is added at the melting or boiling point of a substance?

Answer 5

it causes the substance to change state not temperature

Question 6

Is a change of state a reversible or irreversible reaction?

Answer 6

reversible because it is a physical change that alters the internal energy but not the temperature or mass

Question 7

What is the latent heat of fusion?

Answer 7

the energy needed for a substance to change from a solid to a liquid (melt)

Question 8

What is the latent heat of vaporisation?

Answer 8

the energy needed for a substance to change from a liquid to a gas (evaporate)

Question 9

What parts of heating and cooling graphs indicate where energy is being used to change state?

Answer 9

the horizontal parts

Question 10

What is the temperature in gases related to?

Answer 10

the average kinetic energy of the particles

Question 11

What happens when the particles of a gas collide with the walls of its container?

Answer 11

they exert a force on the wall which is felt as pressure

Question 12

If the temperature of a gas is kept constant, what changes can be made to the volume in order to alter the pressure of the gas?

Answer 12

-increasing the size of the container will reduce the pressure, as the particles will collide with the walls less frequently
-reducing the volume will increase the pressure, as the particles will collide with the wall more frequently

Question 13

If the volume of a gas is kept constant, how will changing the temperature affect pressure?

Answer 13

increasing the temperature increases the speed of the particles this increases the frequency and force with which the particles hit the walls and increases the pressure

Question 14

What happens when work is done on a gas?

Answer 14

it increases the internal energy of the gas and can cause an increase in temperature e.g. when a bicycle pump is compressed, the piston hits the gas particles giving them more energy so the temperature increases. as they are moving faster, the particles collide with objects more frequently and the pressure will increase