1. Endothermic Reactions (need heat) (Absorb heat energy from their surroundings) Solid + heat  Liquid (Fusion/Melting) Liquid + heat  Gas (Boiling/Evaporation/Vaporization) Solid + heat  Gas (Sublimation) These changes need HEATING They need to take in or gain heat (Endothermic)

2. Exothermic Reactions (give off heat) (Release heat energy to their surroundings) Gas  Liquid + heat (Condensation) Liquid  Solid + heat (Freezing/Solidification) Gas  Solid + heat (Deposition) These changes require COOLING In order to COOL OFF, the heat they contain must be given off (Exothermic)

3. Temperature vs Heat What’s the difference? It takes more heat to boil a bucket of water than it takes to boil a cup of water even though they both end up at the same temperature. Why?

4. Temperature vs Heat Temperature 1.Tells how hot or cold 2.Use Thermometer ( o C, o F, or K) 3. Measures the average KE of the particles 3.Kinetic energy = speed of particles 4.As Avg KE increases, temperature increases Heat 1.Heat is a form of energy 2.Use Calorimeter (Joules or Calories) 3.Measures the total KE of all the particles 4.Heat is a transfer of energy (usually thermal energy) from a hotter area to a colder area 5.Thermal energy = energy associated with random motion of particles

5. Temperature vs Heat *** Heat energy always flows from an area of higher temperature to an area of lower temperature! **** Substance Direction of heat flow Substance at 40 o C from hot to cold at 80 o C ***In summary: Temperature depends on the speed of the particles (avg KE) while heat depends on the speed & quantity of particles (total KE).

6. Temperature Scales http://www.youtube.com/watch?v=RO-qC-Wj7Nk&feature=related Carefully draw the diagram. Then, write down the following info: 1.Absolute Zero = Zero Kelvin (molecules stop moving, coldest temp) 2. NBP of water is called an water-steam equilibrium = 100 o C 3. NFP of water is called an water-ice equilibrium = 0 o C 4.Notice: There are 100 degrees between boiling & freezing on both the Kelvin and Celsius scales.

7. Temperature Conversions One degree on the K scale is the same size as one degree on the C scale. Equation K = o C + 273 Given: o C = 26 o C Unknown: K = ? K = 26 + 273 = 299 K

8. Temperature Conversions Equation K = o C + 273 Given: K = 200 K Unknown: o C = ? 200 = o C + 273 o C = 200 - 273 = -73 o C

9. Temperature Conversions If the temp changed from 283 K to 293 K, how many o C did it change ? 293 K – 283 K = 10 K Answer: 10 o C Why?

10. Temperature Question: Which substance has particles with the highest average KE? a) 50 grams of Fe(s) at 35 o C b) 75 grams of Hg (l) at 25 o C c) 100 grams of He (g) 20 o C Answer: A (highest temp)

11. Law of Conservation of Energy 1.Energy cannot be created or destroyed, but may change form 2.The total amount of energy in the universe is constant 3.Energy lost = Energy gained

12. Law of Conservation of Energy Problem: A student puts an ice pack on his swollen ankle. 1)Which way does the heat flow? Answer: From his ankle to the ice pack 2) How does this illustrate the Law? Answer: The heat lost by the ankle = the heat gained by the ice pack.

13. Law of Conservation of Energy Device: Kitchen Toaster 1)What is the energy transformation? Answer: From electrical energy to heat energy 2) How does this illustrate the Law? Answer: Energy is not created or destroyed, but it does change form from electrical to heat energy.