1. Chapter 1.4.2: Temperature in Thermal Systems
Objectives:
Define specific heat, heat of fusion, and heat of vaporization
Use specific heat, heat of fusion, and heat of vaporization to solve problems involving heat transfer.

2. Specific Heat Units for Thermal Energy and Heat
Joule (J)
calorie (cal)
British thermal unit (Btu)
Specific heat, C – amount of energy required to raise the temperature of a unit mass of a substance one temperature unit.
Possible units?
J/g·oC cal/g·oC kJ/kg·oC

3. C is an intrinsic physical property, like  does not depend on amount but only on the substance itself.

4. Table 1.7 Specific Heat of Common Substances
(cal/ g·oC)
Water
1.00
Stone (avg.)
0.19
Ice
0.49
Iron
0.16
Wood (avg.)
0.42
Copper
0.093
Air
0.24
Brass
0.091
Aluminum
0.22
Tin
0.055
Glass
0.21
Lead
0.031

6. Sample Problem
How much energy must be absorbed by 20.0 g of water to increase its temperature from 83.0 °C to 94.0 °C?

7. Sample Problem
The specific heat of iron is 0.16 cal/g·oC. Convert this value to specific heat in J/g·oC.

8. Example 1.15, p. 72
A teakettle hold 0.5 liters of water. How much heat is needed to increase the temperature from 20oC to 100oC. Hints:
water = 1.00 g/ml; and 0.5L = 500 mL

9. Change of State
Linear relationship between heat transfer and temperature does NOT hold during a change of state
Temperature stays constant during the phase change, i.e. T = 0 during the phase change

10. Example for Water Boiling point Melting point/ freezing point Steam
Water and Steam
Melting point/ freezing point
Water
Ice and water
Ice

11. Melting point (m.p.) – temperature at which a substance melts (or freezes if losing energy).
Boiling point (b.p.) – temperature at which a substance turns to gas (or condenses if losing energy).
Heat of fusion, Hf – amount of energy required to melt one gram of solid.
Heat of vaporization, Hv – amount of energy required to vaporize one gram of a liquid.

12. Table 1.8 Heat of Fusion (Hf) and Vaporization (Hv) of Selected Substances
Hf (cal/g)
Hv (cal/g)
Water
79.8
540
Iron, Fe
63.7
1503
Copper, Cu
49.0
1212
Silver, Ag
25.0
564
Gold, Au
15.3
392
Lead, Pb
5.9
207
Back to Problem

13. Sample Problems
Convert the heat of fusion of iron to heat of fusion in kJ/kg.
How much heat is required to vaporize 0.5 kg of gold.

14. Example 1.17 Melting Ice and Warming Water
A 10.0 g ice cube has a temperature of oC. How much heat is needed to melt the ice cube and warm the resulting water to room temperature (20 oC)?

15. Links Virtual experiment: Heating Curves Heating Curve Tutorial
Heating Curve Tutorial
Heat Problems