1. Heat and Temperature

2. What is heat?
The transfer of thermal energy from one object to another because of a difference in temperature.
Heat flows from an area of high heat to an area low in heat.
Result of work that is not 100% efficient

3. What is temperature?
The measure of how hot or cold something is compared to a reference point
Average kinetic energy of particles in an object

4. What is thermal energy?
Total potential and kinetic energy in an object
Depends on mass, temperature, and phase of an object

5. What has more heat (or thermal energy)?
A. An iceberg or
B. A burning match

6. Heat involves temperature AND mass!!!
The Iceberg.
Why?
Because an iceberg is much bigger and has more total molecular vibrations than the small match.
Heat involves temperature AND mass!!!

7. First Law of Thermodynamics
Energy cannot be created or destroyed, but it can be transferred from one location to another and/or converted to another form of energy.

8. So, how is heat transferred?

9. Conduction

10. Conduction - heat transfer through contact.
Heat energy is transferred molecule by molecule

12. Some materials are good conductors while others are good insulators.
Conductors transfer energy very efficiently.
Insulators transfer energy very inefficiently.

13. This is fiberglass insulation
This is fiberglass insulation. It keeps hot air out of your house during the summer. It keeps warm air inside your house during the winter.

14. Convection

15. Convection – Heat carried from one place to another in a liquid or gas as molecules move in currents caused by density differences

17. Radiation

18. Radiation – electromagnetic (EM) waves travel through empty space
Radiation – electromagnetic (EM) waves travel through empty space. Everything with temperature releases EM waves.

19. Three methods of heat transfer
Conduction:
Transfer from one substance to another by direct contact of molecules. Example: When you touch a hot stove.
Convection:
Heat carried from one place to another in a liquid or gas as molecules move in currents caused by density differences. Example: Warm air rising.
Radiation:
Heat carried through empty space in the form of infrared rays. Example: When you face the sun and feel warmth on your face.

20. Second Law of Thermodynamics
The entropy of a system always increases over time.
Entropy: the measure of disorder
Basically, heat can NEVER transfer from a cold object to a hot object

21. Heat energy and phase changes

24. Heating Curve of Water
Heat of Vaporization
Heat of Fusion

25. A cooling curve for the conversion of gaseous water to ice
Figure 12.3
A cooling curve for the conversion of gaseous water to ice

26. Specific Heat The ability of a substance to absorb heat.
The specific heat of a substance is the number of calories (or Joules) needed to raise the temperature of one gram of the substance one degree Celcius.
The units of Specific Heat are:
calories per gram degree Celsius
Joules per gram Kelvin

27. EQUATION
Heat gained or lost = (mass) (change in Temp) (specific heat)
Q = m C ΔT
Heat gained or lost
Change in temp (final-initial)
Mass (g)
Specific Heat capacity

28. Specific Heat Specific Heat of water: 1 calorie=4.186 J/g °C
Ex: Calculate the amount of heat needed to increase the temperature of 250g of water from 20°C to 46°C.

29. Ex: Calculate the amount of heat needed to increase the temperature of 250g of water from 20°C to 46°C. q = m x C x ΔT
q = 250g x 4.18J/goC x 26oC 
q = 27,209 J