The Particle Model of Matter

Question 1

density=

Answer 1

• mass/ volume
• p= m/V

Question 2

why is a change of state reversible and affects the properties of a substance but not its mass

Answer 2

the number of particles does not change during a change of state, only their spacing and arrangement

Question 3

what is internal energy?

Answer 3

the total amount of kinetic energy and chemical potential energy of all the particles in the system

Question 4

where is the internal energy of a system stored?

Answer 4

in the atom and molecules that make up the system

Question 5

what does ΔEt, m, c and ∆θ stand for

Answer 5

change in thermal energy, mass, specific heat capacity, temperature change

Question 6

what does ΔEt, m and l stand for

Answer 6

change in thermal energy, mass, specific latent heat

Question 7

how are watts related to joules?

Answer 7

Watt = 1 Joule per second

Question 8

in a heating/ cooling graph, what is on the y and x axis and what shows changes in state?

Answer 8

• y= temperature, x= time (s)
• horizontal points on the graph show energy is not being used to increase the speed of the particles, increasing temperature, but is being used to break the bonds between the particles to change the state
• the longer the horizontal line, the more energy has been used to cause the change of state

Question 9

what is the difference between specific heat capacity and specific latent heat?

Answer 9

• specific heat = energy needed to change one kilogram of a material by 1°C
• latent heat = energy needed to change the state (gas, liquid, solid) of one kilogram of material

Question 10

explain, with reference to the particle model, the effect of changing the temperature of a gas held at constant volume on it’s pressure

Answer 10

as the temperature increases, the pressure increases showing that pressure is directly
proportional to temperature

Question 11

how to calculate change in pressure or volume of a gas (fixed mass held at constant temp) when either pressure or volume is increased/ decreased

Answer 11

• p1V1= p2V2
• p1 and v1= pressure/ volume before either are changed and 2 is after either are changed
• rearrange this equation to find what you want

Question 12

how can increasing volume in which a gas is contained lead to a decrease in pressure when temperature is constant

Answer 12

the same number of particles collides with the walls of the container less frequently as there is more space even though the particles still collide with the same amount of force

Question 13

explain how work done on an enclosed gas can lead to an increase in temperature of the gas, as in a bicycle pump

Answer 13

• work done means the gas has been compressed which means that the particles collide with the walls of the container more frequently because there is less space which
• this increase in collisions means more kinetic energy and higher temperature
• this process explains why a bicycle pump gets warm when it is used to inflate a tyre