1. Energy and Energy Transfer

2. Basic Principles Energy - the capacity to do work
Kinetic Energy and heat
Kinetic energy is related to heat, but determined by temperature. The higher the temp, the higher the kinetic energy.

3. Conservation of Energy
The 1st law of Thermodynamics
The law of conservation of energy
Energy can be transferred from one form to another, but must be conserved.

4. Temperature and Heat Heat is not the same as temperature
Heat is a measure of energy. Temperature is a relative measurement.

5. Directionality of Heat Transfer:Thermal Equilibrium
Heat transfer always occurs from a hotter object to cooler object
Transfer of heat continues until both objects are at the same temperature
The quantity of heat lost and gained are numerically equal (law of conservation)

6. Heat Transfer
The quantity of heat transferred is described by the equation
q = m . C . D T
q is the heat
m is the mass in grams
C is the specific heat
D T is change in temperature

7. Directionality of Heat Transfer:Thermal Equilibrium
Exothermic process heat is transferred to the surroundings.
Symbol for heat = -q, (heat given to surroundings)
Endothermic process heat is transferred to the system.
Symbol for heat = q, (heat given to system)

8. Energy Units 4.184 Joules = 1 calorie
q is expressed in Joules or calories
Joule is the SI unit for heat or energy
1 calorie the amount of energy required to raise 1 gram of water 1 degree C
Joules = 1 calorie

9. Specific Heat Capacity and Heat Transfer
D T = Tfinal - Tinitial
D T can be positive or negative

10. Units for T and Specific Heat Capacity
C = Specific Heat Capacity
the amount of heat required to raise the temperature of 1 gram of a substance by one degree celcius.
Units are J / g . C

11. Specific Heat Capacity and Heat Transfer
In an experiment it was determined that 59.8 J was required to change the temperature of 25.0 g of ethylene glycol (a compound used as antifreeze in automobile engines) by 1.00 degree C. Calculate the specific heat capacity of ethylene glycol from these data.
Use q = m . C . D T
Solve for C

12. Specific Heat Capacity of a Metal
Problems about adding a hotter metal to a sample of colder water
The water and metal will end up at the same temperature Tfinal
No heat transferred to surroundings
qmetal, has a negative value because the temp of metal dropped; qwater has a positive value
-qmetal = qwater

13. Energy and Changes of State
Heat is required to invigorate molecules to break bonds and separate from each other.
The heat required to convert a substance from a solid at its melting point to liquid is called the heat of fusion.
The heat required to convert liquid at its boiling point to a gas called the heat of vaporization.

14. Energy and Changes of State

15. Energy and Changes of State
Heat of Fusion = 333 J / g or kJ / mol
Heat of vaporization = 2256 J /g
Note the the units for the heats have only 2 values, J and g because there is no D T

16. Energy and Changes of State
What is the minimum amount of ice at 0oC that must be added to the contents of a can of diet cola 340 mL to cool it from 20.5oC ? Assume the Specific Heat Capacity and density of diet cola are te same as for water and that no heat is gained or lost to the surroundings.