1. CHANGES OF STATE ARE PHYSICAL CHANGES
Section 2.2
CHANGES OF STATE ARE PHYSICAL CHANGES

2. II. Solids can become liquids, and liquids can become solids
Examples of solids that can change to liquids
Ice melts into water
Others???

3. A. Melting Melting is the process of a solid becoming a liquid
Different solids melt at different temperatures
Energy is GAINED making the particles move FASTER
Melting point is the lowest temperature at which a substance melts
Substances with a well-defined melting point have an orderly structure

4. B. Freezing Freezing is the process of a liquid becoming a solid
many substances are “frozen” at room temperature
Energy is LOST making the particles move SLOWER
Freezing point is the temp. at which a liquid becomes a solid
Freezing point of a substance equals the melting point of that same substance

5. A. Evaporation Evaporation is the process of a liquid becoming a gas
Usually occurs at the surface
Solids can lose particles at the surface, similar to liquids, by the process of sublimation
Energy is GAINED making the particles move FASTER

6. B. Boiling
Boiling is the process of changing a liquid to a gas by producing bubbles which contain dissolved air
Can occur only when a certain temp. has been reached which is called the boiling point
The boiling point of water at higher elevations is lower because of lower air pressure

7. B. Boiling (continued)
Different substances have different boiling points
a) Helium boils at -270°C (-454°F)
b) Aluminum boils at 2519°C (4566°F)
Energy is GAINED making the particles move FASTER

8. C. Condensation
Condensation is process by which a gas becomes a liquid
Energy is LOST making the particles move SLOWER
Like evaporation, condensation occurs over a wide range of temperatures