2. Phase Changes Notes on 3.3

3. Temperature  Temperature will not change during a phase change.  Once a substance reaches the temperature required for a phase change to happen, the temperature stays at that same point throughout the phase change.  Temperature will not change during a phase change.  Once a substance reaches the temperature required for a phase change to happen, the temperature stays at that same point throughout the phase change.

5. Energy and change of state  Energy is either absorbed or released during a phase change.  During an endothermic change, heat is absorbed.  Example: an ice sculpture melting  Energy is either absorbed or released during a phase change.  During an endothermic change, heat is absorbed.  Example: an ice sculpture melting

6. Fusion is another word for melting.  Heat of fusion is the energy a substance must absorb in order to change from a solid to a liquid.  The heat of fusion is different for different substances. is another word for melting.  Heat of fusion is the energy a substance must absorb in order to change from a solid to a liquid.  The heat of fusion is different for different substances.

7. Energy and Changes of State continued  An exothermic change occurs when a substance releases heat to its surroundings.  Freezing is an example of an exothermic change.  An exothermic change occurs when a substance releases heat to its surroundings.  Freezing is an example of an exothermic change.

8. Evaporation  Evaporation takes place at the surface of a liquid and occurs at temps below the boiling point for that substance.  When water evaporates in a closed container, what collects above the water?  The pressure caused by the collisions of the water vapor and the walls of the container is called vapor pressure.  What happens to the vapor pressure when the temperature is increased? Why?  Evaporation takes place at the surface of a liquid and occurs at temps below the boiling point for that substance.  When water evaporates in a closed container, what collects above the water?  The pressure caused by the collisions of the water vapor and the walls of the container is called vapor pressure.  What happens to the vapor pressure when the temperature is increased? Why?

9. Condensation  Condensation is the phase change where a gas or vapor changes into a liquid.  This is an exothermic process.  Examples include:  The moisture on the mirror after a shower  Morning dew on the grass  Condensation is the phase change where a gas or vapor changes into a liquid.  This is an exothermic process.  Examples include:  The moisture on the mirror after a shower  Morning dew on the grass

10. Deposition  When a gas or vapor changes directly into a solid without first changing into a liquid, deposition has occurred.  This is an exothermic change.  This is what causes frost to form on windows.  When a gas or vapor changes directly into a solid without first changing into a liquid, deposition has occurred.  This is an exothermic change.  This is what causes frost to form on windows.

11.  D. Density  1. Amount of mass in one unit of volume. (Mass/volume)  D. Density  1. Amount of mass in one unit of volume. (Mass/volume)

12.  2. Measured in kilograms per cubic meter. (Kg/m cubed)