1. Ch10 Energy & Causes of Change
Energy has many forms, one of them is thermal energy. Heat is the transfer of this thermal energy which results when two objects of different temperature are brought in contact with each other.
Heat is given the variable Q and is measured in energy units of either calories or joules
1.0 cal = 4.18 Joules

2. Temperature
The temperature of a substance is the average kinetic energy of the particles.
Absolute temperature is proportional to the movement.
Absolute temperature is measured in Kelvin Units.
Tk = Tc
Absolute zero is 0K or -273ºC, all motion stops at this temperature.

3. Direction of Heat Flow
Energy flows from the object with greater kinetic energy to the object with lower kinetic energy.
It is important to define your system.
The system is the experiment, the surroundings are everything else in contact with the experiment.
Ideally the system is isolated from the surroundings; in reality it is insulated from the surroundings.

4. Heat Flow The total amount of energy transferred is always conserved.
The heat energy lost by the warmer object is equal to the amount gained by the colder object.
When heat flows into or out of a system a temperature change is usually noted.
Not all substances change their temperature equally.

5. Heat Flow
There exists a mathematical relationship between heat flow and change in the temperature of a system..
Q = mC∆T
In this case C is the specific heat capacity of the system. It represents the amount of heat energy required to raise 1.0 gram of a substance 1ºC.
m is the mass of the substance and ∆T is the change in Celsius temperature.

6. Heat Flow
The calorie is a unit based upon the specific heat of a substance.
1.0 calorie (cal) is the heat required to raise 1.0 grams of water 1ºC.
1.0 calories = 4.18 Joules
The food calorie (Cal) is actually 1000 heat calories or a kilocalorie.
A table of specific heat capacities is located in your book on pg. 329.

7. Calculation Examples

8. Calorimetry
A device used to isolate the heat flow in a reaction is called a Calorimeter.
The heat loss or gain in the reaction is absorbed or provided by the reaction vessel.
If the calorimeter is an isolated system
Qreaction + Qcalorimeter = 0
Qreaction = - Qcalorimeter

9. “Coffee-Cup” Calorimeter
For simple interactions a coffee-cup calorimeter is often used.
The calorimeter is filled with water in which the reaction is carried out.
The heat gain or loss of the water is equal to the heat gain or loss of the reaction.

10. Solving Calorimetry Problems
Identify the system and the surroundings.
The total change in energy for an isolated system is zero so make an equation with calorimetry terms equal to zero.
Hint: the heat released in a reaction is proportional to the amount of reactant.