1. Energy Transfer and Thermal Equilibrium
Unit 9
Energy Transfer and Thermal Equilibrium

2. Energy and Temperature
Kinetic Energy Increases with temperature
𝑞=𝑚𝑐Δ𝑇

3. Heat (energy) is necessary to melt ice and boil water
Changes of State
Endothermic Process
Heat (energy) is necessary to melt ice and boil water

4. Heat (energy) is produced when condensation or freezing occurs
Changes of State
Exothermic Process
Heat (energy) is produced when condensation or freezing occurs

5. Energy and Phase Changes
Fusion  Heat absorbed converting solid to liquid
Solid + Heat
Liquid

6. Energy and Phase Changes
Vaporization  Heat absorbed converting liquid to gas
Liquid + Heat
Gas

7. Energy and Phase Changes
q  heat absorbed or consumed
c  specific heat in specified physical state
m  mass
DT  change in temperature
DHfusion  heat of fusion(melting)
DHvap  heat of vaporization (boiling)

8. Sample Problem
Calculate how much energy it takes to convert 50 g of -45 ˚C to 170 ˚C.
Cice = 2.09 J/(g ˚C) DHfus = 334 J/g
Cwater = 4.18 J/(g ˚C) DHvap = 2260 J/g
Csteam = 2.03 J/(g ˚C)