1. Kinetic Energy and Phase Changes

2. Diffusion Diffusion is the process by which molecules will move randomly in order to fill the space that they are in

3. Rate of Diffusion How fast diffusion occurs depends on the kinetic energy of the particles – High kinetic energy = Diffusion occurs quickly – Low kinetic energy = Diffusion occurs slowly **Think back to the demonstration we did with the hot and cold water with food coloring. In which beaker did the food coloring spread out the fastest?

4. Phase Changes Melting – Solid  liquid – The kinetic energy of the particles that make up the solid is increased This causes the particles to move around more -- What do you think causes the increase in kinetic energy? Melting point: temperature at which a solid turns into a liquid

5. Phase Changes Evaporation – Liquid  gas – The molecules in a liquid become excited enough, or move around enough, that some of them can escape from the surface of the liquid and become a gas – Do you think this occurs faster on a hot day or a cold day? Boiling point: the temperature at which a liquid turns into a gas

6. Phase Changes Condensation – Gas  liquid – Gas particles slow down and get close enough to each other that they form a liquid – Due to a decrease in kinetic energy – Would this be more likely to occur when it gets very hot or very cold? Why?

7. Phase Changes Freezing – Liquid  solid – The particles that make up the liquid slow down enough that they form a solid – What would cause the particles to slow down?

8. Phase Changes Sublimation – Solid  Gas – Ex/ Dry ice

9. Phase Change Diagram