1. endothermic
2. endothermic
3. exothermic
4. exothermic
5. exothermic
6. endothermic
7. exothermic
8. endothermic
9. exothermic
10. exothermic
11. endothermic
12. endothermic

1. kinetic energy increases, potential energy stays the same
2. kinetic energy stays the same, potential energy increases
3. kinetic energy increases, potential energy stays the same
4. kinetic energy stays the same, potential energy increases
5. kinetic energy increases, potential energy stays the same

1. A has the lowest specific heat capacity of all three and therefore does not require as much heat to raise its temperature. B has the next highest and C has the highest specific heat – so high in fact, that the temperature does not increase at all. It is also possible that liquid C was changing phase (boiling).

2. Condensation is the changing of water vapor (gas) into liquid water. This is a decrease in PE and an exothermic reaction. The system (the water) loses energy in the form of heat and the surroundings (your skin) absorb that heat making you warmer.

3. During all phase changes, the temperature (average measure of kinetic energy) does not change. Instead the energy goes into changing the phase and being stored as potential energy instead of changing the temperature.

4. Energy is required for molecules to react because during the collision the electrons from each molecule repel each other. This requires energy to overcome the repulsion. This energy is called activation energy and it determines the speed at which a reaction occurs. If the activation energy is high, then the reaction will be slow.

1.  Q = m x C x Δt
Q = 25.0 g x 4.184 J/g °C x (-)25 °C
Q = -2620 J
t is negative, so Q is negative as well.
2. Q = m x ΔHfus
Q = 25.0 g x 334 J/g
Q = 8350 J
3. Q = m x C x Δt
-6700 J = 35 g x C x (-) 65 °C
C = 2.9 J/g °C

1. D
2. H
3. E
4. C
5. F
6. G
7. I
8. J
9. B
10. A

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