1. Kelvin Scale
Absolute temperature
§ 17.3

2. Temperature and Gas Pressure
(constant volume)
different samples
Absolute zero
Source: Griffith, Physics of Everyday Phenomena, Fig. 10.6

3. Absolute Zero Gas p decreases with T Absolute zero  T at which p = 0
Minimum total molecular kinetic energy

4. Kelvin scale Unit: K K = same size as °C but 0 K = absolute zero
(T in K) = (T in °C)

5. CPS Question How do the temperatures 273.25 °C and 273.15 K compare?
°C is the same as K.
°C is half K.
°C is twice K.
°C is absolute zero.

6. Thermal Expansion
size does matter
§ 17.4

7. Linear Expansion L0 T0 L0 + DL T0 + DT DL = a DT L0
a = coefficient of linear expansion
valid for small DT

8. CPS Question
A metal ring is heated. What happens to its outer diameter?
It increases.
It stays the same.
It decreases.
Impossible to determine.

9. CPS Question
A metal ring is heated. What happens to its inner diameter?
It increases.
It stays the same.
It decreases.
Impossible to determine.

10. Volume Expansion T0 + DT V0 + DV V0 T0 V0 DV = b DT
If expansion is isotropic,
and DT is small,
b = 3a

11. Water is Weird Density maximum disappears above ~2.5% salt
Source: Young and Freedman, Figure 17.12
Density maximum disappears above ~2.5% salt

12. CPS Question Between 0 °C and 4 °C, warmer fresh water
Rises above colder water.
Sinks beneath colder water.
Has neutral buoyancy.
It is impossible to determine.

13. Thermal Stress
Results from:
Uneven composition
Uneven temperature