Understanding Thermal Energy: Work, Heat, and Temperature Effects

1. Thermal Energy and Matter Ch 16.1

3. Work and Heat • Heat- transfer of thermal energy from 1 object to another due to temperature difference • Heat flows from hot objects to cold objects

4. Temperature • Temperature- measure of how hot or cold an object is compared to a reference point • °C= boiling/freezing point of water • Absolute zero- reference point in K, which is 0K • Temperature relates to the kinetic energy of particles • hot= faster particles • cold= slower particles

5. Thermal Energy • Depends on: • Mass • Temperature • Phase- solid, liquid, gas of an object

6. Thermal Contraction and Expansion • Thermal Expansion- increase volume due to temperature increase • Particles move farther apart • Thermometers • Increase temp. = alcohol moves/expands = temperature you read

7. Specific Heat • Specific Heat- amount of heat needed to raise the temperature of 1g of material by 1°C • The lower the SH, the more the temp. rises when a given amount of energy is absorbed by a given mass

8. Specific Heat Q = m c ΔT Q- heat absorbed by material, J M- mass, g C- specific heat, J/g°C ΔT- change in temp. °C

9. Specific Heat Practice • An iron skillet has a mass of 500g. Its specific heat is 0.449 J/g°C. How much heat must be absorbed to raise the temperature by 95C? • Given: • Formula: • Solve:

10. Math Practice pg 477 • 2. • 4. • 3. • 5.

11. Measuring Heat Changes • Calorimeter- sealed instrument used to measure changes in thermal energy • Uses principle that hot energy flows to cold, until they equal the same temperature.

12. Heat and Thermodynamics Ch. 16.2

14. Conduction • Transfer of thermal energy between 2 touching objects, with no overall transfer of matter • Slower in gases due to particles colliding less often

15. Conduction Thermal Conductors Thermal Insulators • Conducts thermal energy well • Can be hot or cold • Ex: Cu, Al • Tile vs Wood • Conducts thermal energy poorly • Can be hot or cold • Ex: Air, plastic, wool

16. Convection • Transfer of thermal energy when particles of a fluid move from 1 place to another • Hot moves to cold • Convection Current- fluid circulates in a loop as it alternatively heats up and cools down • Oven, heaters • Naturally- ocean currents, weather, molten rock

17. Radiation • Transfer of energy by waves moving through space • Heat lamps • All objects radiate energy- as temperature increases the rate it radiates energy increases

18. Conduction, Convection or Radiation Heating?

19. Thermodynamics Thermodynamics 1st Law of Thermodynamics • Study of conversions between thermal energy and other forms of energy • James Joule, 1800’s • Energy is conserved

20. Thermodynamics 2nd Law of Thermodynamics 4th Law of Thermodynamics • Thermal energy can flow from cold to hot objects ONLY if work is done to the system • Heat engine- device converts heat into work • Waste heat- thermal energy not converted into heat • Absolute zero cannot be reached

21. Using Heat Ch. 16.3

23. Heat Engines External Combustion Engine Internal Combustion Engine • Engine that burns fuel outside the engine • Steam engine • Engine that burns fuel inside the engine • Cars

24. Heating Systems • Central Heating Systems • Heats many rooms from 1 central location • Most use convection to distribute thermal energy

25. Heating Systems Hot Water Heating Steam Heating • Conduction and radiation using water • Conduction and radiation using steam

26. Heating Systems Electric Baseboard Heating Forced Air Heating • Conduction and radiation using electrical energy • Convection using fans

27. Cooling Systems • Heat pumps • Device that reverses the normal flow of thermal energy • Circulates refrigerant through tubing • Refrigerant- fluid that vaporizes and condenses inside the tubing of a heat pump

28. Cooling Systems Refrigerators Air Conditioners • Transfers thermal energy from the inside to the outside • Cools inside, releases hot air