What is the particle theory also known as?
Kinetic theory
What happens when atoms emit electromagnetic radiation?
electrons drop to a lower energy level (closer to the nucleus)
What happens when atoms absorb electromagnetic radiation?
electrons move to a higher energy level (further away from the nucleus)
Describe a solid
- strong forces of attraction between particles
- the particles are held tightly against one & other in a fixed position creating a fixed structure
- definite shape and volume
- particles are able to vibrate in their fixed positions
What happens when a solid is heated?
melting
- particles gain more energy and vibrate more which weakens the bonds between them
- once the solid reaches the melting point its bonds would be broken so it can flow
Describe a liquid
- weak forces of attraction between particles
- free to move but the particles tend to stick together
- have a definite volume but their shape can change, allows them to flow and fill a container
What happens when a liquid is heated?
Evaporation
- particles gain kinetic energy so they move around faster
- boiling point- liquid becomes a gas
Describe a gas
- very weak forces of attraction
- free to move around
- do not have a definite shape or volume and always fill a container
- constantly moving with random motion (any direction)
What happens when gas is heated?
- it could expand (in an expandable container)
- the pressure will increase (in a fixed container)
What is it called when a gas is cooled down?
condensation
What is it called when a liquid is cooled down?
Freezing
What is it called when a substance goes from a solid to a gas?
sublimation
When working in a closed system what do changes in state do?
- do not change the mass
- changes the density of the substance:
- solid = highest density
- liquid = lower density
- gas = lowest density
What kind of change is a change in state?
physical- the material recovers its original properties if the change is reversed
What does pressure produce in a gas?
a net force at right angles to the wall of the gas container
equation for a fixed mass of gas held at a constant temperature?
pV= constant
What is pressure measured in?
Pascals
What does doing work on a gas do?
increases the internal energy of the gas and can cause an increase in the temperature of the gas
What is the equation for density?
mass/volume
mass- kg
volume- m3
How do you calculate the density of a solid?
- find the mass by placing it on a mass
- for regular shapes, measure and multiply the length, width and height
- mass/volume
How do you calculate the density of an irregular object?
- Fill the Eureka can (displacement) with water, directly in line with the spout
- place a measuring cylinder beneath the spout
- measure and record the mass of the solid using a balance
- tie string around the object and immerse it into the can
- the volume of displaced water= volume of the object
- calculate density using mass/volume
How do you calculate the density of a liquid?
- place an empty measuring cylinder onto a balance and zero the balance
- pour some of the liquid into measuring cylinder (e.g. 10ml) and record the mass
- divide the mass by the volume
- larger the volume → more accurate density (because it minimises the effects of uncertainty)
How does heating change the energy stored within a system?
- increases the energy of the particles that make up the system
- either raises the temperature or produces a change of state
What is specific latent heat?
The amount of energy required to change the state of 1kg of the substance with no change in temperature
