1. Temperature “How hot or cold something is”
Measures avg. K.E. of the particles in the object.
Tool: thermometer – meas. in degrees.
Scales
~ Celsius (°C) 0° - 100°
~ Fahrenheit (°F) 32° - 212°
~ Kelvin (K) 273 K – 373 K
0 K – Absolute zero

2. Temperature Scales

3. Internal Energy Grand total KE & PE inside a substance.
Depends on temp & amount of substance.
Which beaker has more internal energy? Why?

4. Heat Amount of internal energy required to change temp.
A substance does not contain heat – it contains internal energy.

5. Heat
Thermal Contact – objects in contact or mixed. Heat flows from higher temp. substance to low temp. substance.
Thermal Equilibrium – thermal contacts reach same temp. – no heat flow.
Qlost = Qgained
There is no net change in energy! Energy is conserved!

6. Changes in Heat
The internal energy changes when heat flows into or out of objects.
Q = mc∆t
Q = heat transferred (calories or joules)
m = mass (g)
C = specific heat (cal/g-°C) or (J/g-°C)
∆t = change in temp. (°C)

7. Specific Heat Capacity
Ability of a sub. to store internal energy.
The amount of heat needed to raise the temp. of 1 g of the material 1 °C.
Units: cal/g-°C.
Specific Heat of Materials
Substance
Specific Heat (cal/g-°C)
Water
1.00
Wood
.42
Aluminum
.22
Glass
.16
Iron
.11
Copper
.09
Silver
.06 or
J/g-°C

8. Units of Heat
calorie - the amount of heat needed to raise the temperature of 1 g water 1 °C.
Kilocalorie = Calorie (food unit).
1 Kcal = 1000 calories
Joule J = 1 calorie.

9. Calculate Heat Transferred
How much energy would it take for 1 kg of aluminum to change from 22 °C to 32 °C?
Q = mc∆t
Q = 1000 g · .216 cal/g-C · 10 °C
Q = 2,160 calories

10. Calculate Heat Transferred
Let’s compute how much energy it takes to make a cup of coffee or tea. Eight ounces of water has a mass of 0.22 kg. How much heat must be transferred to water to raise its temperature from 20 °C to 100 °C?
Q = mc∆t
Q = 220 g · 1 cal/g-C · 80 °C
Q = 17,600 calories

11. Methods of Mixtures mc∆t = mc∆t
A 50 g piece of metal immersed in boiling water is placed in 100 g of water at 20 °C. The final temperature of metal and water is 28 °C. What is the specific heat of the metal? What is the metal?
QL = QG
mc∆t = mc∆t
(50g)(c)(72 °C) = (100 g)(1.0cal/g ·°C)(8 °C)
c = .22 cal/g ·°C aluminum

12. Methods of Mixtures
A 50.0 g block of iron at 80 C is dropped into a cup of 200 g of water at 22 C. The block cools to 40 C. What would be the temperature change of the water?
QL = QG
mc∆t = mc∆t
(50 g)( .11 cal/g·°C)(40°C)=(200g)( 1cal/g°C)(∆T)
∆T = 1.1 °C
22 °C °C = °C is Tf

13. Methods of Mixtures
Jerry grabs a hot g brass spoon from his bowl of soup, originally at a temperature of 95.0 C. To avoid burning his fingers he drops the spoon into a sink of 1,250 g water at 18.0 C. One second later, the spoon has cooled to a temperature of 75.0 C. Calculate the temperature of the water at this time.
QL = QG
mc∆t = mc∆t
(350 g) ( .09 cal/g·°C) (20°C) = (1250g) ( 1cal/g°C) (∆T)
∆T = .504 °C
18 °C °C = °C is Tf

14. Mechanical Energy Relates to motion Potential Energy = mgd
Kinetic Energy = ½mv2
Work = F x d
W = PE = KE
Unit: Joule (J)

15. Thermal Energy Relates to motion of molecules Q = mc∆t
Unit: calorie or Joules

16. Conservation of Energy
Energy can’t be created or destroyed, but can change forms, including between thermal and mechanical.
Elost = Egain
Qlost = Qgain
KE = Qgain
PE = Qgain
W = Qgain

17. Mechanical Equivalent of Heat
Relationship of mechanical energy to thermal energy.
W = PE = KE = Q
1 calorie = J

18. Mechanical – Thermal Energy
A 5 kg concrete block falls 10 m to the ground. If all of the block’s energy is converted into heat that is absorbed by the block only, it’s temperature is raised _____?
PE = Q
mgd = mc∆t
5 kg · 9.8 m/s2 · 10 m = 5 kg · 670 J/kg-°C · ∆t
∆t = 0.15 °C

19. Thermal Expansion
Expansion of a substance due to heat.

20. Phase Expansion ↑heat energy - ↑kinetic energy - ↑motion.
Gas/Liquid/Solid
↑temperature – expand
↓temperature – contract

21. Thermal Exp. of Water
As the temp. decreases from 4°C to 0°C, water expands - ice.
Its density decreases.
The maximum density of water (1.0 g/mL) occurs at 4°C.

22. Uses of Thermal Exp. Thermometer Sidewalk joints Building materials
Thermostat – bimetallic strip
Consequences??

23. Expansion Rates
Different materials expand at different amounts with the same temperature rise.
Thermal Coefficients for Length & Volume.
Solids (length) L = LO x  x T
L = change in length
L0 = original length
 = coefficient of linear expansion
T = change in temperature

24. Linear Expansion Coefficients
Material Coefficient ( C –1 )
Aluminum x 10-6
Brass x 10-6
Copper x 10-6
Glass x 10-6
Gold x 10-6
Iron (Soft) x 10-6
Lead x 10-6
Quartz x 10-6
Steel x 10-6

25. Expansion Rates
The Eiffel Tower, constructed in 1889 by Alexandre Eiffel, is an impressive latticework structure made of steel. If the tower is 301 m high on a 22 oC day, how much does its height decrease when the temperature cools to 0.0 oC?
L = LO x  x T
= 301 m • 10.5 x10-6 • 22 °C
= m