Unit 2 Overview and Objectives—Energy ---- It’s Just a Phase
Unit Test: Oct 14 (A day) and Oct 15 (B day)
Objectives
1. Identify the following physical processes:
a. Evaporation
b. Boiling
c. Freezing
d. Melting
e. Condensation
2. Describe how energy is transferred and
stored between system and surroundings
through the process of heating/cooling.
a. Thermal energy
b. Phase energy
3. Describe the characteristics of solids, liquids
and gases in terms of particles and their
attractions
4. Given a heating/cooling curve for a
substance identify:
a. phase(s)
b. melting/freezing temperatures
c. which energy storage mode (thermal
or phase) is changing
5. Determine whether a process is
endothermic or exothermic.
Video Clips to check out to help your understanding:
Heating and Cooling curves described:
http://www.kentchemistry.com/links/Matter/HeatingCurve.
Discussion endothermic/exothermic:
http://www.docbrown.info/page03/3_52states.htm#2a.
Heating curve Video:
http://www.youtube.com/watch?v=DgPTAqIqBGQ
Endothermic/exothermic process video:
http://www.youtube.com/watch?v=0cUK4jcAEaU
Phase Change video:
http://youtu.be/EZHmUTmJtF8
Review Questions
1. Label which phases are present in
each portion of the curve.
2. Label the sections in which the
thermal energy (Eth) of the sample is
changing
3. Label the sections where the phase
energy (Eph) is changing.
4. Where is thermal energy increasing
or decreasing?
5. Where is the phase energy
increasing/decreasing?
6. Where is the energy being absorbed?
7. Define the following terms
a. melting point
e. sublimation
b. evaporation
f. exothermic process
c. boiling point
g. endothermic process
d. vaporization
8. What happens to the temperature of water when it is boiling?
9. Is making ice an endothermic or exothermic process?
10. During condensation, does the water absorb energy from the surroundings or does the water
release energy to the surroundings?
11. What happens to a water sample’s thermal energy of liquid while freezing?
12. What happens to a water sample’s thermal energy of liquid while warming?
13. On the graph below left sketch the curve that describes the following:
Initial state: 150 g solid water at –10 ˚C
Final state: 150 g liquid water at 0˚C
Temp
Time
Temp
14. On the graph to the right sketch the curve that
describes the following:
Initial state: 200 g liquid water at 40 ˚C
Final state: half of the water has boiled away at 100˚C
Time