1) States of Matter

Describe solids

Solids have a fixed volume and shape, they have a high density.

Particles are very close together; they are arranged in a regular pattern and can only vibrate about a fixed position. Particles have very low energy.

Describe liquids

Liquids have a fixed volume, but it adopts the shape of the container it is in. They have medium density.

Particles are close. They are randomly arranged and they move and slide past each other, which allows them to flow freely. Particles have more energy than in solids.

Describe gases

Gases do not have a fixed volume or shape. It takes up the shape of the entire container, and they have low density.

Particles are far apart. They are randomly arranged and move randomly in all directions. Energy of particles are very high.

Describe melting (change of state)

Melting occurs when a solid changes into liquid. When a solid is heated, particles gain energy and vibrate more. As the temperature increases, the particles vibrate so much that the solid expands, and bonds between particles break. The particles move further apart and the solid melts into a liquid.

Describe boiling and evaporation (change of state)

Boiling occurs when a liquid changes into a gas. When a liquid is heated, the particles vibrate further and it continues to expand. The intermolecular forces between particles break, which is when it starts to evaporate. Evaporation only occurs at the surface of liquids where high energy particles can escape from areas of low temperature. Once the boiling point is reached, all particles gain enough energy to move apart and the liquid boils into a gas.

Describe condensation

Condensation occurs when a gas changes into a liquid. When a gas is cooled, its particles lose energy/transferred to surroundings and move closer to each other. There is not enough energy to move apart, so they get closer together, and the gas condenses into a liquid.

Describe freezing

Freezing occurs when a liquid changes into a solid. When a liquid is cooled, particles lose more energy/transfer more energy to the surroundings and bonds reform, and the liquid freezes into a solid.

Describe the motion of gaseous particles

Constant and random motion

Explain pressure in gases

Inside a closed container, pressure is created by the gas particles colliding with the walls of the container; the more collisions the more the pressure.

When the volume of the container is decreased, the particles collide with the container wall more frequently, increasing the pressure.

Explain temperature in gases

Increasing the temperature increases the kinetic energy of gaseous particles. As the temperature increases, the gas particles move faster and spread out more.

If the particles are in a container, increasing the temperature will cause the particles to collide with the container walls more frequently, which increases the pressure.

What is diffusion

Diffusion is the movement of particles from an area of high concentration to an area of low concentration.

Describe the effect of temperature on diffusion

The rate of diffusion increases when the temperature increases because particles have more kinetic energy, so they move faster and travel down a concentration gradient faster.

How does the concentration of particles change by diffusion

The concentration of particles in the available space eventually becomes even as the particles evenly spread out.

Where can diffusion occur

Diffusion can occur in liquids and gases, but it is fast in gases as gases have more energy and move quicker than liquids.

The effect of relative molecular mass on diffusion

Different gases diffuse at different rates at the same temperature due to their relative molecular masses.

Gases with a lower relative molecular mass have lighter particles, so they travel faster and further in a given time; they diffuse faster

Gases with a higher relative molecular mass have heavier particles, so the travel slower and don't travel as far in the same amount of time; they diffuse slower