1. Heat Energy and Phase Changes
Energy is the ability to do work.
Measured in Joules.

2. Georgia Performance Standards
SPS7. Students will relate transformations and flow of energy within a system.
a. Identify energy transformations within a system (e.g. lighting of a match).
b. Investigate molecular motion as it relates to thermal energy changes in terms of conduction, convection, and radiation.
c. Determine the heat capacity of a substance using mass, specific heat, and temperature.
d. Explain the flow of energy in phase changes through the use of a phase diagram.

3. Georgia Performance Standards
SPS5. Students will compare and contrast the phases of matter as they relate to atomic and molecular motion.
a. Compare and contrast the atomic/molecular motion of solids, liquids, gases and plasmas.

4. Temperature
a measure of the average kinetic energy of the particles in an object
As kinetic energy (motion) increases, temperature increases and vice versa
A thermometer measures temperature
Mercury
Alcohol

5. Temperature Scales Celsius Scale (or Centigrade) ºC Freeze Water- 0 ºC
Boil Water- 100 ºC
Metric

6. Temperature Scales Kelvin Scale
The lowest possible temperature is ºC
This is Absolute Zero- kinetic energy is zero, particles no longer move Kelvin, 0 K
Absolute Zero is the basis of the Kelvin Scale
Metric
The magnitude of a degree Kelvin is the same as that of Celsius

7. Kelvin is the bigger scale.
Temperature Scale Conversions K ºC
K-273
ºC+273
From Celsius to Kelvin… add 273
From Kelvin to Celsius…subtract 273
Remember:
#273
Kelvin is the bigger scale.

8. Math Skills Convert from Celsius to Kelvin
5 oC = __________
110 oC =_________
20 oC=___________
Convert from Kelvin to Celsius
350 K= __________
280 K= __________
125 K= __________

9. HEAT determined to be a form of energy
BACKGROUND… people believed that heat was a colorless, odorless gas called Caloric… that would flow into objects and heat them up then flow out and cool down…NOT TRUE.
Count Rumford- concluded that heat was a form of energy
Motion can produce heat
Amount of heat depends upon the amount of motion
Heat is a form of energy caused by the internal motion of molecules of matter

10. Heat Unlike temperature, heat depends on mass
Example: 50 g of water at 90 oC has more heat energy than 5g of water at 90 oC
More heat energy = more severe burn

11. Energy Transfer Temperature changes indicate energy transfer
Heat always moves from WARMER to COLDER
Energy transfers when particles collide

12. Energy Transfer
(1) Conduction- transfer of energy as heat through solid material
Examples: ironing, touching hot pan…
(2) Radiation- the energy that is transferred as electromagnetic waves
Needs no air
Example… microwave, fireplace, radiator..

13. Energy Transfer
(3) Convection- heat transfer through liquids and gases…
Examples.. Central air and heat, space heaters, blow dryer, convection currents (in water and air), boiling water, taking hot bath…
While making smores you see tiny embers rising
Convection Current- the vertical movement of air currents due to temperature variations
Hot air rises taking the heat with it, Cool air replaces the air, the cool air is heated and then also rises, etc.

14. Back to #1 Conduction: Conductors and Insulators
Conductor- transfers thermal energy easily
Most Metals
Insulator- DOES NOT transfer heat energy easily
Attic insulation
Plastic
Rubber
Wood
Cotton
Pure water

15. Specific Heat
Specific Heat- Quantity of heat required to raise1 gram of material by one degree Celsius
LOW SPECIFIC HEAT heats up quickly but loses heat as quickly (METALS have low specific heat)
Mercury has very low specific heat… good for thermometers
HIGH SPECIFIC HEAT heats up SLOWLY but retains heat longer (Water has high specific heat)

16. Heat lost or gained Formula Heat = mc∆T m= mass c= specific heat
∆ = change in
T= temperature
If I heat 110 grams of water from 25 degrees Celsius to 60 degrees Celsius, then I heat 120 grams of mercury from 20 degrees Celsius to 60 degrees Celsius. Which would heat up faster given the same heat source?
How much heat is lost if I cool 85 grams iron from 180 degrees Celsius to 64 degrees Celsius?
How much heat is gained if I heat 74 grams of silver from 110 degrees Celsius to 154 degrees Celsius?

17. Heat and Phase Changes Matter exists in 4 phases: solid, liquid, gas
(and plasma) (plasma is high energy phase of matter found in stars and sun)
A change in thermal energy causes a phase change
Generally speaking…
Least heat…SOLIDS  LIQUIDS  Gases … MOST heat

18. Phase changes Melting Freezing
Vaporization (Boiling and Evaporation) Condensation
Sublimation
Freezing point- temp at which a liquid turns to solid
Melting point- temperature at which solid turns to liquid
Boiling point- temperature at which liquid phase turns to gas

19. Thermal Expansion Increase in size of substance caused by heat
Most substances- Solid, Liquid, and Gas – Expand when heated
Exception: Ice – expands when it cools from 4 oC to 0 oC, it

20. Math Skills
The highest atmospheric temperature ever recorded on earth was 57.8 ºC. Express this temperature in degrees in Kelvins.
How much heat is gained if I heat 92 grams of copper from 40 degrees Celsius to 98 degrees Celsius?