What does the kinetic theory state?
Everything is made of many small particles which are constantly moving
Describe the arrangement for solids
Forces of attraction hold the particles very closely together - they vibrate but do not move around which explains why solids can keep their shape but not be compressed
Describe the arrangement for liquids
- Particles are moving faster and so forces of attraction between the particles are not strong enough to keep the fixed position
- the particles can move past each other so liquids flow and take shape of their container
- the particles are still close together so cannot be compressed
Describe the arrangment for gases
- particles are far apart and moving around quickly
- gases are compressible and expand to fill their container
Explain how a state change is a physical change
The particles end up in a different arrangement, but the number of particles does not change (mass conservation) - no new substances are made, and the substance can recover its original properties
What is the density of a substance
The mass of a certain volume of the substance
When is a substance the most and least dense?
Most - solid
Least - gas
How do you investigate the densities of solids and liquids
- put an empty beaker on a balance and set it to 0
- use a measuring cylinder to measure 50cm3 of a liquid and pour it into a beaker and write down the reading on the balance which is the mass of 50cm3
- find the mass of the solid and write it down
- stand a displacement can on the bench with its spout over a bowl and fill it with water until the water just starts to come out the spout
- hold a cylinder under the spout and carefully drop the solid into the can and if it floats, push it down (your finger shouldn’t be in the water though)
- stand the cylinder on the bench and read the volume of the water collected which is the same as the volume of your solid
What is the formula for density?
density = mass / volume
What is thermal energy
Energy transferred to a system by heating that is stored in the movement of particles
What happens to the vibrations of the particles when the thermal energy increases?
The vibrations increase
What is the temperature a measure of?
A measure of the movement of the particles
How do you maintain a store of thermal energy
The amount of energy transferred to the surroundings by heating needs to be reduced by surrounding the warm object by insulating materials such as wool, foam or bubble wrap
What does the amount of thermal energy stored in an object depend on?
- its temperature
- its mass
- material its made of
What is the specific heat capacity of an material
The amount of energy it takes to increase the temperature of 1kg of the substance by 1 degree
When does the temperature change during a state change?
The temperature increases as more energy is being supplied to the solid, but while it’s melting, the temperature stays constant because the energy is being used to break the arrangement
What is the specific latent heat
the amount of energy it takes to make 1kg of a substance, change state
Which needs more energy, evaporation or melting?
Evaporation
How do you melt ice before finding the specific heat capacity
- Put a boiling tube full of crushed ice into a heatproof beaker and note the temperature
- Put the beaker on a tripod and gauze and pour hot water from a kettle and keep it warm using a bunsen burner
- Measure the temperature every minute and stop after three minutes when all the ice is melted
- make sure you have noted the time when the ice appeared to start melting and when it has now fully melted
How do you take the measurements for calculating the specific heat capacity
- put a polystyrene cup in a beaker on a battery scale balance note it down and then change it to 0
- add water to the cup and measure the mass
- put a thermometer in the cup and use a 12V electric heater making sure its fully submerged under the water and connect it to a joulemeter
- record the water temperature, turn on the heater and then gently stir the water using a thermometer
- after 5 minutes, check the temperature and record it also checking the joulemeter
What is the temperature of a gas a measure of?
The average kinetic energy of the particles in the gas - the faster the average speed, the higher the temperature (heating the gas increases the kinetic energy and so the temperature increases)
What is the pressure of gas based on?
Due to forces on the walls of a container caused by the moving particles hitting the walls - the faster the particles are moving, the more frequent the collisions will be and so exert more force when they collide
What does increasing the temperature of a gas do?
Increases the speed of the particles and so increases the pressure
What is the unit for pressure
Pascals (1Pa = 1 N/m^2)
