1. 1 15 Temperature, Heat, Expansion Temperature & Heat Internal Energy & Specific Heat Homework: RQ: 1, 2, 7, 8, 10, 12, 15, 21, 24.

2. 2 Temperature T ~ Ex: hammered metal Expansion with T increase

3. Superheating Mythbusters Instant coffee 3

4. 4 Water Expansion Water expands from 4°C to 100°C (as does most materials) However, water contracts when warmed from 0°C to 4°C. (transient ice melting)

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6. 6 Heat ‘heat’ is a transfer of thermal energy due to temperature difference Examples: ice in warm liquid: heat flows from liquid to the ice warm liquid is put in a refrigerator: heat flows from drink to the cold air in refrigerator //

7. 7 Internal Energy the total of all molecular energies, kinetic plus potential, that are internal to a substance. It is ~ (mass) x (temperature). Heat ≠ Internal Energy, however, for a thermal-only process, Heat =  (Internal Energy)

8. 8 mixing: ‘hot’ and ‘cold’ = ‘warm’ for liquids & solids: heat ~ (mass)x(temperature change) when ‘hot’ and ‘cold’ are mixed, heat lost by ‘hot’ = heat gained by ‘cold’ Ex. 1kg water at 0°C is mixed with 1kg water at 20°C: (1kg)(T - 0) = (1kg)(20 – T)

9. 9 Calories and Joules 1 Calorie = _______ calories 1 calorie = ________ joule Calorie is the common food unit. Btu’s are also used, e.g. gas range

10. 10 Specific Heat quantity of heat required to raise the temperature of 1kg by 1°C. //

11. 11 c = Q/(m  T) [J/(kg·K)] c = heat/(massx temperature change) Water: 4186 J/kgC heat needed per kg to raise temperature by 1 degree C or K. specific heat

12. 12 summary T ~ KE/molecule most substances undergo thermal expansion (note the water exception) heat is an exchange of thermal energy superheating specific heat = heat needed to raise temp. of 1kg by 1C (substance dependent)