3. Particle model of matter (internal energy and gas pressure) Flashcards
What is internal energy?
Where a system of particles will always store energy as long as the temperature is above absolute zero
What 2 types of energy can internal energy be split into?
- Kinetic energy
- Potential energy
What is the internal energy as a system?
The total kinetic energy and potential energy all the particles contain
What is the process called when solids turn into liquids?
Melting
What is the process called when liquids turn into gases?
Evapouration
What is the process called when a liquid turns into a solid?
Freezing
What is the process called when a solid turns into a gas?
Sublimating
What is the process called when a gas turns into a liquid?
Condensing
What happens when the internal energy of a system is changed?
A substance changes from one state to another
What happens to the internal energy from a solid - liquid - gas?
There is an increase in the internal energy
What happens to the internal energy from a gas - liquid - solid?
There is a decrease in the internal energy
Describe what is happening in this graph
- The substance is being heated up
- The temperature remains constant until all of the substance melts
- The liquid substance is being heated up
- The temperature remains constant until all of the substance boils
What is potential energy?
All the forces between the particles that make up a system
How is potential energy in solids, liquids and gases?
- Solids: very strong
- Liquids: slightly weaker
- Gases: very weak
What is a boiling point?
The temperature at which a pure substance boils or condenses
What is a melting point?
The temperature at which a pure substance melts or freezes
What is the equation for specific latent heat?
E = ML
Energy (j) = mass (kg) x specific latent heat (j/kg)
What is specific latent heat of fusion?
The amount of energy required to melt 1kg of a solid into a liquid
What happens when we heat a substance in terms of particles?
- When we heat a substance, the temperature increases
- So the particles gain more kinetic energy because they are moving/colliding with each other more
What happens to the temperature when a substance changes state?
- The temperature stops increasing and stays constant
- Now the energy that we are putting in is weakening/breaking the forces of attraction between the particles
What is the specific latent heat of a substance?
The amount of energy required to change the state of 1kg of a substance with no change in temperature
What is the specific latent heat of vapourisation?
The energy required to change 1kg of a substance from a liquid to a vapour with no change in temperature
Why is a change of state an example of a physical change?
-because no new substances are formed and the change can be easily reversed
- it’s the same substance as you started with, just in a different form
- because the particles are arranged differently
Why is mass conserved during changes of state?
Because the number of particles doesn’t change, they are just arranged differently
What causes gas pressure?
The pressure of a gas is due to particles colliding with the walls of the container that the gas is being held in
What do the particles collisions cause?
- A force which creates right angles to the walls of the container
- The force acting over the area of the container causes gas pressure
What happens if the gas is in a container with a bigger volume (and if temperature is constant)?
- then the pressure is reduced because the spacing between the particles has increased
- so particles travel much further before colliding with the walls of the container
- this reduces the number of collisions per second between the particles and the container, reducing the pressure
What is the pressure of a gas inversely proportional to?
To the volume, if the volume increases than the pressure decreases
What is the equation for pressure?
PV = constant
pressure (pa) x volume (m^3) = constant
