Key Terms
Heat
The spontaneous transfer of energy due to a temperature difference. Heat only exists in transit; it is not stored in an
Specific heat c
The heat required to change 1.00 kg of a substance by 1 degree C. Units: J/(kg degrees C) or kcal/(kg degrees C)
ENERGY IS RELEASED on the reverse
Freezing releases L_f, condensation releases L_v. Same magnitude; opposite direction.
Sublimation
Direct solid to vapor transition (skips liquid phase). Q = mL_s where L_s = heat of sublimation.
Good conductors of electricity (metals
Silver, copper, gold, aluminum) are generally good thermal conductors. Good electrical insulators (wood, plastic, rubber
If all spatial dimensions of a conductor double
Area increases by factor 4, thickness increases by factor 2. Net effect on conduction rate: multiplies by 4/2 = 2.
Natural convection is driven by buoyancy
Lower density at higher temperature.
Example from text
15 m/s wind at -10 C has the same chilling effect as still air at about -45 C.
Evaporation plus convection
Sweating cools the body only if moving air carries away the saturated air. Without airflow, air becomes humid and evapor
Thunderstorms
Water evaporates from ocean (absorbing heat), rises by convection, condenses at altitude (releasing L_v), which warms su
Black surfaces
Best absorbers AND best emitters. White surfaces: worst absorbers AND worst emitters (reflects most radiation).
Identify
Mass, specific heat from table, temperature change.
Calorimetry (two objects exchanging heat)
Q_gained + Q_lost = 0; solve for T_f.