1. Heating up the classroom with Thermal Energy

2. TEMPERATURE Measure of kinetic energy of molecules Thermometer
Fahrenheit
Celsius
Kelvin

3. On the Kelvin scale, there is a reference point called absolute zero, which is defined as a temperature of 0 Kelvins. Absolute zero is impossible to reach.

4. Thermal Energy Measurement related to the quantity of molecules.
Thermal energy depends on the mass, temperature, and phase(solid, liquid, or gas) of an object.
As the temperature of an object rises so does its thermal energy.

5. HEAT Thermal energy always moves from warmer to cooler objects.
Heat is the result of molecules vibrating quickly.
Heat is moving energy.
Transfer is the result of a difference in temperature.

6. Calorimeter
A calorimeter is an instrument used to measure changes in thermal energy.
Uses the principle that heat flows from a hotter object to a colder object until both reach the same temperature.
According to the law of conservation of energy the thermal energy released by a test sample is equal to the thermal energy absorbed by its surroundings. Calorimeter is sealed to prevent thermal energy from escaping.

7. A heated piece of aluminum is placed in water
A heated piece of aluminum is placed in water. The change in temperature of the water is measured. Thermal energy absorbed by the water is calculated using the specific heat equation.

8. Calorimeter

9. Count Rumford (Benjamin Thompson)
Count Rumford used a drill to make a cannon in 1798.
He discovered that heat cannot be a form of matter.

10. Thermal contraction and expansion
Thermal expansion is an increase in the volume of a material due to a temperature increase.
Thermal expansion occurs when particles of matter move farther apart as temperature increases.
Thermal expansion is used in glass thermometers. As temperature increases, the alcohol in the tube expands and its height increases. The increase in height is proportional to the increase in temperature.

11. Specific Heat
– The ability of a substance to absorb heat energy (specific heat)
Different substances absorb heat at different rates
-amount of energy required to raise the temp. of 1 kg of material by 1 degree Kelvin
– units: J/(kg·K) or J/(g·°C)

12. Land heats up and cools down faster than water
Specific Heat
Some things heat up or cool down faster than others.
Land heats up and cools down faster than water

13. Why does water have such a high specific heat?
water metal
Water molecules form strong bonds with each other; therefore it takes more heat energy to break them. Metals have weak bonds and do not need as much energy to break them.

14. -The greater the mass of the object the more heat is absorbed
Specific Heat Cont….
-The lower a material’s specific heat, the more it’s temperature rises when a given amount of energy is absorbed by a given mass
-The greater the mass of the object the more heat is absorbed

15. Temperature Conversions
Formula (273+ºC)= Kelvin

16. How to calculate changes in thermal energy
Q = m x T x Cp
Q = change in thermal energy
m = mass of substance
T = change in temperature (Tf – Ti)
Cp = specific heat of substance

17. Practice Problems
A piece of iron at a temperature of 145°C cools off to 45°C. If the iron has a mass of 10g and a specific heat of J/g·oC, how much heat is given up?
2. How much heat is required to warm 230 g of
water from 12°C to 90°C?
3. A 32-g silver spoon cools from 60°C to 20°C.
How much heat is lost by the spoon?

18. Conduction
The transfer of heat by direct contact between objects or particles.

19. Radiation Heat transferred through space.
EXAMPLE: The sun’s rays causing a sunburn.

20. Convection
Heat transferred by the movement of molecules within a substance.
Movement occurs from warmer areas to cooler areas.

21. Convection Current
The movement of a substance that is caused by differences in temperature and density.
EXAMPLES: wind boiling water
NATURE WANTS
EVERYTHING TO BALANCE ! !

22. Conductors Conductors are materials that transfer heat easily.
Examples: metals like copper and gold

23. Insulators
An insulator is a material that does not transfer heat easily.
Examples:
liquids and gases
A jacket

24. Review What type of heat transfer is involved?
1. Heating a room with a fireplace
2. Egg cooking in a frying pan
Roof of a house becoming hot
What is the formula for converting a Celsius temperature to a Kelvin temperature?
What is the boiling point of water on the Kelvin scale?
What is the freezing point of water on the Kelvin scale?

25. Questions
What are the three types of heat transfer?
How is conduction different from radiation?

26. References
Wilmot High School
Lexington