TOPIC 3 - PARTICLE MODEL OF MATTER Flashcards
What is internal energy?
Internal energy is the energy stored by the particles that make up a system.
The particles in a system vibrate or move around - they have energy in their kinetic energy stores. They also have energy in their potential energy stores due to their positions.
the energy stored in a system is stored by its particles. The internal energy of a system is the total energy that its particles have in their kinetic and potential energy stores.
What is the process called where a solid changes into a gas?
Sublimating.
What type of change is a change of state?
A physical change. The number of particles does not change - they are just arranged differently which means the mass is conserved.
What happens when a substance is melting or boiling?
When a substance is melting or boiling, you are still putting in energy and so increasing the internal energy, but the energy is used for breaking intermolecular bonds, rather than raising the temperature. This means that when represented on a graph, parts of the graph are ‘flat’ because energy is not being used to change the temperature.
What happens when a substance is condensing or freezing?
When a substance is condensing or freezing, bonds are forming between particles, which releases energy. this means that the internal energy decreases, but the temperature does not go down until all the substance has changed state. The ‘flat’ parts on the graph show the energy transfer.
What is the latent heat?
The energy needed to change the state of a substance is called latent heat.
What is specific latent heat?
The specific latent heat is the energy needed to change the state of a 1kg Mass.
For cooling, this is the energy released by the change in state.
What is the specific latent heat for changing between a solid and a liquid? (melting or freezing)
Specific latent heat of fusion.
What is the specific latent heat for changing between a liquid and a gas? (evaporating, boiling or condensing)
Specific latent heat of vaporisation.
What happens when you increase the temperature of a gas?
The average speed of its particles increases.
How is pressure created in gases?
By particles colliding together. When they collide with something, they exert a force.
Increasing temperature will increase the speed (more frequent collisions) so also increase in net force and gas pressure.
Increasing the volume means the particles become more spread out, so the pressure decreases.
What is the relation between pressure and volume?
Pressure and volume are inversely proportional. When volume goes up, pressure goes down. For a gas of fixed mass at a constant temperature, the relationship is
pV = constant
p= pressure in pascals V= volume
What can a change in pressure lead to?
A change in pressure can cause a change in volume.
The pressure of a gas causes a net outwards force at right angles to the surface of its container. There is also a force on the outside of the container due to the pressure of the gas around it.
If a container can easily change its size eg a balloon, then any change in these pressures will cause the container to compress or expand, due to the overall force.
What happens when you do work on a gas?
Doing work on a gas increases its temperature. By transferring energy, increases the internal energy, which can increase its temperature. Eg with a bike pump. The gas applies pressure to the plunger of the pump, and so exerts a force on it. Work has to be done against the force to push down the plunger.
