1. Ch.12:Thermal Energy What is the unit for Thermal Energy?

2. ENERGY THERMAL ENERGY Kinetic Theory of Matter: –all matter consists of moving particles –atoms and its parts are always moving Temperature and heat are based on this theory

3. DEFINITIONS THERMAL ENERGY (J) –The total internal energy of an object (microscopic) –Includes chemical potential and internal kinetic energy HEAT (J) –Transfer of thermal energy –Equivalent to “work” TEMPERATURE ( o F, o C, K) –Measure of the kinetic energy inside of an object –Change in temperature relates to heat

4. TEMPERATURE SCALES FahrenheitFahrenheit –first temperature scale CelsiusCelsius –metric system KelvinKelvin –scientific scale

5. Specific Heat amount of energy that must be added to the material to raise the temperature of a unit mass by one temp unit. heat gained/lost by an object depends on the mass, change in temp, and the specific heat.  Q = m C  T Q = heat [J] m = mass [kg] C = specific heat (heat capacity)  T = T f – T i = temperature [K]

6. Some samples of specific heats (p318) Make sure units are same as specific heat

7. Changing Phase (State) Gas Evaporate (heat of vaporization: the amount of energy needed to turn liquid into gas, different for every material) Liquid Melt (heat of fusion: the amount of energy needed to turn solid into liquid, different for every material) Solid Particle speed increases Increasing energy

8. Latent Heat To complete a phase change, more energy is required. There will be no temperature change during a phase change. (if temperature change, use Q = mC∆T) Q = m L, where Q is the heat added (J), m is the mass (kg), and L is the Latent Heat of Fusion (solid- liquid) or Vaporization (liquid-gas) in J/kg.

9. Latent Heat of Fusion and Vaporization

10. PRACTICE PROBLEMS Q = mC  T: –p319 #3-4 –p321 #6-7 Q = mL: –p325 #19-20 –p328 #23,25

11. HW: chapter 12 p336-338 52. 1.64x10 4 J 53. 1003.2 J/kgK 56. 63 ℃ 58. 0.87 L 61. 6.68x10 6 J 63. 29.4 ℃ 64. 3.09x10 4 J 68. 0.016 ℃ 70. 1.1 kg, you need more ice than tea which would get watery, so wait

12. Thermal Energy Travels By: 1)Conduction: energy transferred through a solid by contact 2)Convection: energy transferred through fluid motion 3)Radiation: energy transfer without a medium by electromagnetic waves

13. 4 Laws of Thermodynamics 0 th : If T A = T B and T B = T C, then T A = T C. 1 st : The change in thermal energy of an object is equal to the heat added to the object minus the work done by the object. 2 nd : Natural processes go in a direction that maintains or increases the total entropy (measure of the disorder in a system) of the universe. 3 rd : Absolute zero is a limit that can be approached, but not reached, by massive particles.

14. CREATING CONVECTION CURRENTS Materials: –beaker –colored ice cubes –thermometer Objective: –to observe convection currents –to see the affect/effect of an ice cube in water

15. PROCEDURES Record water temperature at the bottom, middle, and top of the water Put ice cube CAREFULLY on the top Do not stir nor disturb the beaker Observe what happens Measure the water temperature at the bottom, middle and top of the water Repeat for salt water

16. FILL-IN CHART

17. LAB QUESTIONS What happened to the colored ice in the fresh and salt water? Did you observe convection currents? Of the three liquids in this activity, which is the most dense? If left for 30 minutes, what would happen?