1. Unit 7:Thermal Energy From your past: (??) * Energy: the ability to do work * Forms of energy: KINETIC: thermal, electric, radiant, mechanical, sound POTENTIAL: chemical, gravitational, stored mechanical, nuclear **THIS UNIT CONCENTRATES ON THERMAL ENERGY.

2. 1) Heat vs. Temperature HEAT  Defintion: energy transferred between matter because of a difference in temp  Measured by a calorimeter  Unit: calorie, joule (4.18 cal = 1 J) TEMPERATURE Def. measure of the average kinetic energy of particles in matter; shows the tendency of a substance to gain or lose heat *measured by: thermometer  units: C, K, F

3. 2) KINETIC THEORY: EVERYTHING IS MOVING

4. 3) INTERNAL ENERGY  The sum of the KE and PE of particles in an object  What is EXTERNAL energy? This includes the motion of the earth, air resistance, etc.

5. 4) 3 METHODS OF HEAT TRANSFER: **remember: C C R A) Conduction: the transfer of heat by direct molecular contact; chain reaction

6. B) convection:  The transfer of heat by the BULK MOTION of liquids and gases

7. c) Radiation  The transfer of heat that does NOT require a medium

8. Conduction, convection and radiation

9. 5) Count Rumford (Sir Benjamin Thompson)  He said that heat is a form of energy and that energy is the ability to do work. He said heat is produced when work is done. James Prescott JOULE’s experiments proved that motion is due to heat.

10. Count Rumford…  He was born in Massachusetts  During the American Revolution, he was a Loyalist to the British cause and returned to England after the war  Knighted by King George III  “Counted” in Germany  Invented the kitchen range, double boiler, drip coffeepot, Rumford chimney

11.  Rumford Chimney: was all the sensation in London! He figured out how to restrict chimney opening to increase the “up draught”; more effective way to heat a room.

12.  Rumford chimney Rumford chimney

13. 6) Thermal conductivity  Describes how well a substance conducts heat **A high TC = a good conductor

14. **A low TC = a good INSULATOR

15. 7) Thermometry  The study of temperature scales  Types of thermometers: -mercury thermometers (illegal in HS) -alcohol thermometers (now used in HS) -digital thermometers

16. 7) THERMOMETRY  The study of temperature and temp scales  The mercury thermometer used to be the one of choice.  Why do we now have alcohol thermometers? Expands at a gradual rate per degree….

17. Temperature scales  To go from F to C: C = 5/9 (F – 32) To go from C to F: F = 9/5 C + 32 To go from C to K: K = C + 273 (practice will come later )

18. Put a name with a face…  Anders Celsius  Daniel Gabriel Fahrenheit  William Thomson, Lord Kelvin

19. Why is the Celsius scale called the CENTRIGRADE scale?  it because of the 100-degree interval between the defined points. (O C is freezing and 100 C is boiling)

24. Absolute Zero  The temperature at which there is NO MOVEMENT at all  This has never been achieved  0 on the Kelvin scale = absolute zero

26. Time for some temp conversions…

27. 8) Units of Heat  Joule  cal  1 cal = 4.18 J  Calorie= kilocalorie  1000 ergs = 1 J (ergomaster??)

28. The calorie or the Calorie?  Calorie: amount of heat/energy needed to raise the temp of one gramm of water 1 degree Celsius  # of calories in food—measure of how much potential energy that food possesses  Example: can of soda: 200 Calories= 200,000 cal= 200kcal  food pkgs show CALORIES (capital C!)….actually the kilocalorie  Food Calorie and more Food Calorie and more

29. Now on to Thermodynamics  Use orange powerpoint

30. 10) Specific Heat Capacity  The ability of a material to conduct heat  Samples with a high TC will have a low specific heat capacity  Samples with a low TC will have a high specific heat capacity  Consider why…. (you’ll need to know this in your future!)

31.  Unit: J/g C  What does this mean??  Water’s specific heat capacity is 4.18 J/g C. This means it will take 4.18 J of energy to raise the temp of 1 g of water one degree Celsius  Your blanks: energy/absorbed/temp/gram/Celsius  Different materials have different specific heats. See reference tables.  FORMULA: Is this different on your reference table?

32. Time for some problems…Yea!!  FUN TIMES!

33. 11) Law of Heat Exchange  Heat lost = heat gained

34. Types of reactions/heat exchange Endothermic  Heat goes in, added  Endergonic  Photosynthesis  cooking Exothermic  Heat goes out, is lost  Exergonic  Greater entropy  Less enthalpy

37. 12) Calorimeter  Used to measure changes in heat energy  Basic principle: heat lost = heat gained

38. 13) Changes of state/phase A) Freezing: liquid to solid B) Melting: solid to liquid

39. More state changes… C) boiling/evaporation: liquid to gas D) condensation: gas to liquid

40. Even more state changes… E) sublimation: solid to gas; Ex. Dry ice, mothballs

41. The last phase change…. E) Deposition: gas to solid; Ex. hoarfrost