Classify each as exothermic or endothermic.
1. evaporation
2. Kinetic energy is converted into potential energy.
3. Water freezes.
4. Products are more stable than reactants.
5. Combustion
6. Heat seems to disappear.
7. Foot/Hand warmer packets
8. Melting ice
9. Candle flame
10. 
Reaction Path
11. 
Potential Energy
12. Instant cold compress packs
In each section of the diagram, tell what is happening to the kinetic and potential energy of water molecules.
- kinetic energy _________ potential energy ____________
- kinetic energy _________ potential energy ____________
- kinetic energy _________ potential energy ____________
- kinetic energy _________ potential energy ____________
- kinetic energy _________ potential energy ____________
Short Answer Questions
1. Three liquids of the same mass absorb the same amount of heat. Liquid A’s temperature rises 20°C, liquid B’s rises 10°C, and liquid C’s doesn’t change. Explain.
2. Why does the air inside the shower feel warm as the water vapor condenses?
3. Why does the temperature of boiling water not change, even though the water is being heated?
4. We know that molecules must collide in order to react. Why is energy required to make this happen? What is the energy called and how does it affect reaction rates?
Calculation problems:
1. Calculate the amount of heat released when 25.0 g of water at 25.0°C cools to 0.0°C.
2. Calculate the amount of heat released when the same sample freezes.
3. What is the specific heat capacity of a 35 g sample of an unknown metal that releases 6700 J of heat when it cools from 94 °C to 29 °C.
(Hint: If heat is released, it will have a negative value.)
Matching:
1. A form of energy associated with the motion of atoms or molecules and capable of being transmitted through solid and fluid media by conduction, through fluid media by convection, and through empty space by radiation.
2. Everything outside the thermodynamic system.
3. The amount of heat required to convert a unit mass of a solid at its melting point into a liquid without an increase in temperature is known as heat of
4. Denoting a chemical reaction that releases heat into its surroundings.
5. A graph showing how a substance’s phases (gas, liquid or solid) change while being heated is known as this type of curve.
6. The energy possessed by a body because of its motion, equal to one half the mass of the body times the square of its speed.
7. Any set of interrelated parts. The open type allows mass and energy to circulate into and out of it; a closed type gives and receives energy but not mass.
8. A type of diagram or graph showing the pressures at which phase transitions between different states of a pure compound occur, as a function of temperature.
9. Also known as transition state–an energetically excited state which is intermediate between reactants and products in a chemical reaction
10. The theoretical temperature at which substances possess no thermal energy, equal to −273.15°C or −459.67°F or 0 K is known as this.
A. Absolute zero
B. Activated complex
C. Exothermic
D. Heat
E. Heat of fusion
F. Heating curve
G. Kinetic
H. Surroundings
I. System
J. Phase diagram