1. Heat and Thermodynamics

2. Warm-up Below is a graph of temperature (y) versus time as energy is added. Which letters correspond to a phase change of that material? a) A and C b) B and D c) A and B d) C and D COMPARE TEMPERATURE AND HEAT A B C D T (K) t in seconds

3. How to we measure energy? Energy is measured in Joules However heat and energy have several other units as well BTU’s Calories /kcals calories We measure our food in terms of Calories because this is the amount of energy it takes to break it down.

4. Level 1 Complete the level 1 worksheet for Heat (15 minutes to do so) The faster you work the less homework you will have. http://www.stricklandphysics.net/uploads/8/3/5/2/83 52741/heat_math_introduction.pdf http://www.stricklandphysics.net/uploads/8/3/5/2/83 52741/heat_math_introduction.pdf

5. Equations

6. Specific Heat (Review) Specific heat is defined as the amount of energy (in Joules) that it takes to raise the temperature of 1 gram substance by 1 degree C, or by 1 K.

7. Substance c in J/g m K c in cal/ gm K or Btu/ lb F Mol ar C J/m ol K Aluminum 0.90 0 0.21524.3 Bismuth0.123 0.02 94 25.7 Copper 0.38 6 0.09 23 24.5 Brass 0.38 0 0.09 2... Gold 0.12 6 0.03 01 25.6 Lead 0.12 8 0.03 05 26.4 Silver 0.23 3 0.05 58 24.9 Tungsten 0.13 4 0.03 21 24.8 Zinc 0.38 7 0.09 25 25.2 Mercury 0.14 0 0.03 3 28.3 Alcohol(ethyl)2.40.58111 Water 4.18 6 1.0075.2

8. Phase Change Latent Heat (L) measured in J/kg indicates the amount of energy required to cause a substance to change phases Two types Fusion and Vaporization L is typically large compared to Cp

9. Calorimetry The heat lost by the hotter object will be gained by the cooler one Each Q represents heat T f for each one is the final temperature of both. T i is unique for each compound and is given in the problem This is how they find how many calories are in your food!

10. Calorimetry Example (LEVEL 2) A piece of copper has a mass of 20 kg and is warmed to 140 degrees C. It is placed in 200 kg of water that is at 2 degrees C. What is the final temperature of both materials?

11. Phase Change Energy (Level 2) If nitrogen starts out as a gas at 300 K. How much energy is required to liquefy 2 kg of nitrogen if nitrogen has a specific heat of 1,040 J/Kg K and a Latent heat of vaporization of 200,000 J/kg. Nitrogen boils at 77 K.

12. Group Work Practice Practice your skills at Level 2 Questions http://www.stricklandphysics.net/uploads/8/3/5/2/83 52741/group_work_l2_heat.pdf http://www.stricklandphysics.net/uploads/8/3/5/2/83 52741/group_work_l2_heat.pdf