# Physics Topic 3 - Particle Model of Matter

What is density?
A measure of the 'compactness' of a substance. It relates the mass of a substance to how much space it takes up.
1 of 16
What is the equation for density?
Density (kg/m^3) = mass (kg) / volume (m^3)
2 of 16
What does the density of an object depend on?
What it's made of, and how it's particles are arranged.
3 of 16
Describe a solid.
Strong forces of attraction hold the particles close together in a fixed, regular arrangement. The particles don't have much energy so they can only vibrate around their fixed positions. The density is generally highest in this state.
4 of 16
Describe a liquid.
There are weaker forces of attraction between the particles, and they are close together but can move past each other and form irregular arrangements. They have more energy than the particles in a solid and move in random directions at low speed.
5 of 16
Describe a gas.
There are almost no forces of attraction between the particles, they have more energy than in liquid and solid and are free to move. They travel in random directions at high speeds and gases are generally less dense than liquids.
6 of 16
How does a change in state happen?
If the substance is heated enough, the particles will have enough energy in their kinetic energy stores to break the bonds holding them together.
7 of 16
How does state change due to cooling?
The particles lose energy and form bonds
8 of 16
What do the flat parts on a temp/time graph show?
These show the change in state, as when the substance is melting or boiling, you're still putting in energy and therefore increasing the internal energy, but it's being used for breaking intermolecular bonds rather than raising the temperature.
9 of 16
What is specific latent heat?
The energy needed to change the state of 1kg of a substance without raising its temperature.
10 of 16
What is the formula for specific latent heat?
Energy (J) = mass (kg) x specific latent heat (J/kg)
11 of 16
How do gas particles cause pressure?
Gas particles collide with the container and they exert on a force on it. In a sealed container, the outward gas pressure is the total force exerted by all of the particles on a unit area.
12 of 16
How is pressure increased?
Faster particles and more frequent collisions lead to an increase in net force, and therefore pressure. Increasing temperature will increase the speed, and so the pressure.
13 of 16
How does increasing volume affect pressure?
An increase in volume will mean the particles are more spread out and therefore hit the walls of the container less often, so the gas pressure decreases.
14 of 16
What is the relationship between volume and pressure?
They are inversely proportional.
15 of 16
How does a change in pressure 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 on the container due to the pressure of the gas around it. A change in these pressures causes a change in volume
16 of 16

## Other cards in this set

### Card 2

#### Front

What is the equation for density?

#### Back

Density (kg/m^3) = mass (kg) / volume (m^3)

### Card 3

#### Front

What does the density of an object depend on?

### Card 4

#### Front

Describe a solid.

### Card 5

#### Front

Describe a liquid.