particle model of matter

what is density?

mass for a given volume

Why do solids have a high density?

particles are very packed together, have a high mass for their volume

Why do gases have low density?

the particles are very far apart, have a small mass for their volume

why does polystyrene have a low density despite it being a solid?

it is a very open structure with lots of air spaces

equation for density

density = mass/volume

what are usually the units for density

kg/m^3

how to determine the density of a regular object?

determine the mass using a balance and work out the volume by measuring each slide and multiplying them together

how to determine the density of an irregular object?

determine the mass with a balance but use displacement to determine the volume

how do you use displacement to determine the volume of an irregular object?

fill an eureka can with water, place the object into the water and measure the water the flows out of the spout in a measuring cylinder

what is internal energy?

the total kinetic and potential energy of all the particles that make up a system

how does internal energy in a solid change as it is heated?

it increases

how does internal energy in a gas change as it is cooled down?

it decreases

what happens to the mass of a solid when it is heated into a liquid?

mass is conserved - it stays the same

why is a change of state being physical change important?

this means that it is able to recover it's original properties and that changes are reversible

what is evaporation?

when a liquid turns into a gas but only on the surface

why does evaporation take place?

only the particles on the surface have enough internal energy to turn into a gas

what is specific heat capacity?

the amount of energy required to increase the temperature of 1kg of a substance by 1 degree

equation for specific heat capacity

energy = mass x specific heat capacity x change in temperature

how do we see the solid change to a liquid on the heating graph?

temperature of solid rises as the energy of particles rise as well line of graph becomes horizontal as the solid is fully melted

what allows a substance to change state?

energy we are putting in to weaken or break the forces of attraction between the particles

what energy is needed for a substance to change state?

latent heat

what happens to the temperature of a substance when it changes state?

the temperature stops increasing and stays constant

what is specific latent heat?

the energy needed to change the state of a 1kg mass

what is specific latent heat of fusion?

The specific latent heat for changing between a solid and a liquid

what is specific latent heat of vaporisation?

The specific latent heat for changing between a liquid and a gas

equation for specific latent heat?

energy = mass x specific latent heat

what is pressure in a gas?

when the particles hit the side of their container at a right angle, they exert a force on the wall, which is felt as pressure

how can we increase the pressure of a gas?

increase the number of collisions per second or the energy of each collision

how does a low temperature of a gas effect it's pressure?

low temperature particles have lower kinetic energy resulting in fewer collisions per second and an overall lower pressure

how does a high temperature of gas affect it's pressure?

high temperatures have higher kinetic energy resulting in more collisions per second and an overall higher pressure

what happens to the pressure of gases when we increase the volume of a container?

it reduces

why does the pressure reduce when we increase the volume of the container it's in?

there is an increase in spacing between particles which mean particles have to travel a lot further to collide with the walls of the container - reducing the number of collisions per second

what is the relationship between the pressure of gas and the volume?

pressure of gas is inversely proportional to the volume

what does the pressure of gas being inversely proportional to the volume mean?

if the volume increases the pressure decreases

equation for pressure of gas

pressure x volume = constant

what is important to remember about the equation for pressure of gas?

it can only be applied if the temperature is kept constant

what rule should we apply instead of the equation for pressure of gases if the temperature is not constant?

if we double the pressure we halve the volume

what is work?

the transfer of energy by a force

what happens to the particles in a gas when you apply force to it?

energy is transferred to them which increases the internal energy of the gas and therefore increases it's overall temperature

what is the relationship between the temperature of gas and it's particles?

temperature of gas = the average kinetic energy of particles

why does a bicycle pump get warm when you use it?

they are doing work on a gas and increasing it's internal energy