1. Thermochemistry
Chapter 10
thermo #1.ppt
thermo #1.ppt

2. Today, you will learn…
The definition of energy The major types of energy The difference between temperature and heat The definition of a state function

3. The study of heat energy released or required
THERMOCHEMISTRY
The study of heat energy released or required
by chemical reactions
Energy is often released as heat and light.
Combustion - Fuel is burned (reacts with oxygen) to produce energy.
CH4(g) O2(g) CO2(g) + 2H2O(l) + energy
Combustion of a hydrocarbon always produces CO2 and H2O!

4. Energy due to position (stored energy)
Kinetic energy (KE)
Potential energy (PE)
Energy due to motion
Energy due to position (stored energy)

5. Symbol is T
Units are in C or K
Measures AVERAGE kinetic energy of the particles in a substance.
Temperature
Symbol is Q
Units are calories (cal) or Joules (J)
Measures TOTAL kinetic energy of the particles in a substance
Heat

8. Thermal Energy Relationships
If temperature increases…
Thermal energy also increases
Why? The kinetic energy of the particles increased
If the temperature stays the same…
More mass (more particles) = more thermal energy.
Example: A whole pan full of boiling water would cause more damage than a drop of boiling water

9. Total Energy = Kinetic Energy + Potential Energy
E = KE PE
Kinetic energy & potential energy are interchangeable
Ball thrown upwards slows & loses kinetic energy but gains potential energy
The reverse happens as it falls back to the ground

10. Law of Conservation of Energy : the total energy of the universe is constant and can neither be created nor destroyed; it can only be transformed.
This is also known as the First Law of Thermodynamics.

11. internal energy, E, of a sample is the sum of all the kinetic and potential energies of all the atoms and molecules in a sample
TOTAL energy of all the atoms and molecules in a sample
Includes not only heat energy, but also energy in other forms (such as the energy stored in chemical bonds.)

12. Energy is a state function
State function – depends only on initial and final conditions
- independent of pathway
Distance between cities is a state function…
Distance you travel is not!