1. Chapter 9 Heat!

2. Temperature and Thermal Energy Although closely related, these things are NOT the same thing!!!!

3. Thermal energy The TOTAL amount of energy of the molecules of a substance

4. heat The internal motion of molecules or the transfer (flow) of thermal energy

5. temperature The AVERAGE kinetic (moving) energy of the molecules in a substance

6. temperature does not measure heat or thermal energy & =

7. Temperature vs. thermal energy Temperature measures, on average, how much the molecules are moving Thermal Energy is the total amount of energy (moving and not moving) that molecules have

8. energy Energy depends on mass. Therefore an object/substance with more mass has more thermal energy

9. A very hot (temp) substance with a small mass actually has less thermal energy than a very cold substance with a large mass

10. temperature conversions

11. Degree Celsius ( o C) based on the freezing and boiling points of water Degree Fahrenheit ( o F) based on the human body Kelvin (K) based on water, but no negative values Absolute zero or 0 K when all molecular motion stops --> Theory, scientists have not reached this temperature Temperature units

12. conversions Celsius = K - 273 Kelvin = o C + 273 Celsius = 5/9 ( o F - 32 o ) Fahrenheit = 9/5 ( o C + 32 o )

13. Chapter 9.5 Heat units are energy units

14. The unit to measure heat is a calorie or a joule. Calorie: the amount of heat needed to change the temperature of 1g of water by 1º C 1 Calorie = 4.18 Joules

15. Laws of Thermodynamics 1 st Law: Whenever heat flows into or out of a system, the gain or loss of thermal energy equals the amount of heat transferred 2 nd Law: Heat never spontaneously flows from a cold substance to a hot substance 3 rd Law: No system can reach absolute zero

16. Specific Heat

17. Specific Heat: The ability to absorb heat energy In other words: how well a substance abosorbs heat or heats up Specific Heat Capacity: The quantity of heat energy required to raise 1g of a substance 1ºC (Units for specific heat capacity are cal/gºC or J/gºC) In other words, can the substance hold a lot or a little heat energy before there is a change in temperature The specific heat capacity for water is 1 cal/gºC. Think of this as your reference. It is considered HIGH.

18. An object that heats up slowly has a HIGH specific heat capacity. It needs a lot of heat energy to raise the temperature of the substance. EX: Water, Wood An object that heats up quickly has a LOW specific heat capacity. It needs a littler heat energy to raise the temperature of the substance. EX: Metal, Black-top, Sand Think about this...

19. calculations Q = m * ∆T * Cp Q heat energy calories m mass grams ∆T change in temp. ºC Cp specific heat capacity cal/gºC or J/gºC C water 1 cal/gºC or 4.184 J/gºC **When ∆T is positive, heat energy is gained (Q is positive) **When ∆T is negative, heat energy is lost (Q is negative)

20. PRACTICE If you wish to warm 100,000 g of water by 20 o C, how much heat is required (give answer is Joules and in Calories) A.59 kg brass candlestick has an initial temperature of 98.0°C. If 21,100J of heat is removed from the candlestick to lower its temperature to 6.8°C, what is the specific heat capacity of brass (answer in J/g o C)?

21. PRACTICE A.225kg sample of tin, which has a specific heat capacity of 2.300J/(g o C) is cooled in water. The amount of heat transferred to the water is 3900J. what is the change in temperature of the tin?

22. Chapter 9.8 thermal expansion

23. Molecules in a hot substance jiggle faster and move farther apart, resulting in thermal expansion. Most substances expand when heated and contract when cooled.

24. A bimetallic strip is a device made of strips of different metal welded together. When heated, one side of the strips bends more than the other. This device can be used to turn a pointer, regulate a valve, or close a switch.

25. Liquids expand more than solids with an increase in temperature.

26. Between 0ºC- 4ºC, water occupies a greater volume than in a liquid phase, due to an open crystalline structure. When water freezes to become ice, its volume increase tremendously, lowering its density, which is why ice floats on water. Solid ice contracts with further cooling. Water is less dense at 0ºC, which is why ice forms at the surface of water, not at the bottom.