Topic 11 - Particle Model, Forces of Matter Flashcards
kinetic theory
everything is made of tiny particles
explain a solids arrangement, movement and properties
- forces of attraction hold particles closely together -> the particles can vibrate in a fixed position
- this explains why solids keep their shape and cannot be compressed
explain a liquids arrangement, movement and properties
- the particles are moving faster and so the forces of attraction between the particles are not strong enough to hold them in fixed positions
- the particles can move past each other so liquids flow and take the shape of their container
- particles are still very close together, so liquids usually can’t be compressed.
explain a gases arrangement, movement and properties
- the particles are far apart and moving around quickly
- compressible
- expand to fill their container
what happens to the particles when a substance undergoes a change of state (arrangement & mass)
- end up in a different arrangement
- same number of particles so the mass stays the same (mass is conserved)
-> physical change, because no new substances are formed and the substance recovers its original properties if the change is reversed
density
The mass of a certain volume of the substance
when are the substances the most dense
when they’re solid because the particles in solids are close together
density equation
density = mass (kg)
volume (m3)
CORE PRACTICAL - Investigating densities method
Liquid:
- Put an empty beaker on a balance, and set the balance to zero.
- Use a measuring cylinder to measure 50 cm of a liquid and then pour it into the beaker. Write down the reading on the balance. This is the mass of 50 cm’ of the liquid
Solids:
- Find the mass of the solid and write it down
- Stand a displacement can on the bench with is spout over a bowl
- Fill it with water until the water just starts to come out of the spout
- Hold a measuring cylinder under the spout and carefully drop your object into the can. If your object floats, carefully push it down until all of it is under the water. Your finger should not be in the water.
- Stand the measuring cylinder on the bench and read the volume of water you have collected. This is the same as the volume of your object. Write it down.
thermal energy
Energy transferred to a system by heating will be stored in the movement of the particles that make up the substances in the system
what happens to the vibrations in a solid when the solid stored more thermal energy
vibrations increase
temperature of a substance
measure of the movement of the particles due to energy stored
how to maintain a store of thermal energy
The amount of energy that is transferred to the surroundings by heating needs to be reduced -> this can be done by surrounding the warm objects with insulation interiors such as wool, foam or bubble wrap
What does the amount of thermal energy stored in something depend on?
- It’s temperature
- It’s mass
- the material it is made from
specific heat capacity of a material
amount of energy it takes to increase the temperature of 1kg of a substance by 1°C
how does temperature cause change of state
When enough energy is transferred to solid it reaches its melting point; if energy continues to be transferred, the temperature stops rising because the extra energy is used to overcome the forces between the particles and turn the solid into a liquid
specific latent heat
Amount of energy it takes to make 1kg of a substance change state
change in thermal energy equation
change in thermal equation (J) = mass (kg) x specific heat capacity (J/kg °C) x change in temperature (°C)
Thermal energy needed for a change of state equation
Thermal energy needed for a change of state (J) = mass (kg) x Specific Latent heat (J/kg)
CORE PRACTICAL - Investigating water method
Melting ice:
- boiling tub full of crushed ice into a heatproof beaker put a thermometer in the ice and note the temperature
- Put the beaker onto a tripod and gauze, pour hot water from a kettle into the beaker and keep it warm using a Bunsen burner
- Measure the temperature of the ice every minute, record your results in a table, stop taking readings three minutes after all the ice is melted
- note the times at which the ice starts to melt and when it appears to be completely melted
Specific heat capacity:
- put a polystyrene cup in a beaker onto a battery powered balance and zero balance then fill the cup almost to the top with water and write down the mass of water, carefully remove the cup from the balance
- put a thermometer in the water and support it, put a 12 V electric immersion heater into the water making sure the heating element is completely below the water level, connect the immersion heater to a joulemeter
- Record the temperature of the water and then switch the immersion heater on, stir the water in the cup gently using the thermometer
- After five minutes, record the temperature of the water again and also write down the readings on the joulemeter
What is the measure of the temperature of a gas?
The temperature of a gas is a middle of the average kinetic energy of the particles in the gas
-> force of the average speed of the particles higher the temperature
What increases the kinetic energy of the particles in a gas?
Heating a gas increases the kinetic energy of the particles so they move faster and the temperature rises
pressure of a gas
due to the forces on the walls of a container caused by the moving particles hitting the walls
