SP14- Particle Model Flashcards
What’s sublimation
When a solid goes solid to gas
What does the kinectic theory state
Everything is made of tiny particles
Why can’t solids usually be compressed
In solids forces of attraction hold particles closely together and particles can vibrate but they can’t move around . Solids can keep their shape but usually not compressed
When is mass conserved
In physical and chemical changes - chemical changes often can’t be reversed argh!!!
What’s density
The density of a substance is the mass of a certain volume of the substance, almost all substances are most dense when they are solids and least dense when they are gases
Sold usually denser than the same substance as a liquid as particles less closer - water and ice is an exception
How is density calculated
Density = mass / volume
What’s temperature a measure of
It’s a measure of the movement of particles - it’s not the same as thermal energy
Eg a kettle full of boiling water stored more energy than a cup of water at the same temp
How can we 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 object with an insulating materials such as wool, bubble wrap or foam
Insulation is also used in fridges to stop energy from the surroundings being transferred to the inside of the ford he by heating
What’s does the amount of thermal energy stored in something depend on
It’s temperature
It’s mass
The material it’s made from
What’s specific heat capacity
The amount of energy it takes to increase the temperature of 1 KILOGRAM of a substance by 1 DEGREE C
Why does temperature stop rising when a substance is changing state
BEcause the extra energy is used to overcome the forces between the particles and then the solid into a liquid
What’s specific latent heat
The amount of energy it takes to make 1 kg of a substance change state
There’s SLH of vaporisation (liquid to gas)
SLH of melting
Takes MORE energy to melt than evaporate
What’s the SLH of evaporation and melting equal to
The energy given out again when the substances condenses or freezes
How can the change in thermal energy be calculated
Q= m x SHC x change in temperature
How is thermal energy needed to change state calculated
Thermal energy needed for a change of state = mass x SLH
