1. THermo
By Mr. M

2. Heat Form of energy and measured in Joules
There is no such thing as cold
There are objects with heat and objects with less heat
Heat transfers from hot object to less hot object until the temperatures reach equilibrium
Heat can transfer three ways
Conduction = transfer by touching
Convection = transfer by heating gas
Radiation = light waves

3. Land heats up and cools down faster than water
Specific Heat
a. Some things heat up or cool down faster than others.
Land heats up and cools down faster than water

4. Specific heat is the amount of heat required to raise the temperature of 1 kg of a material by one degree (C or K).
1) C water = 4184 J / kg C
2) C sand = 664 J / kg C
This is why land heats up quickly during the day and cools quickly at night and why water takes longer.

5. How to calculate changes in thermal energy
Q = m x T x Cp
Q = change in thermal energy
m = mass of substance
T = change in temperature (Tf – Ti)
Cp = specific heat of substance

6. C. Heat Transfer
How much heat is required to warm 230 g of water from 12°C to 90°C?
GIVEN:
m = 230 g
Ti = 12°C
Tf = 90°C
Q = ?
Cp= 4184 J/kg·K
WORK:
Q = m·T·Cp
m = 230 g = 0.23 kg
T = 90°C - 12°C = 78°C
Q = (0.23kg)(78°C)(4184 J/kg·K)
Q = 75,061 J

8. Types of Rxns Exothermic = rxns that release energy
Usually in the form of heat, light, or fire
Endothermic = rxns that absorb energy

9. Collision Theory All rxns are cause by atoms colliding
Energy is exchanged when atoms collide
A rxn is spontaneous if it happens all on its own, but you can force a rxn to happen if you increase collisions (change the energy)

10. Collision Model
model used to explain current known characteristics of reaction rates (speed of reactions)
based on the idea that molecules must collide in a certain way for a reaction to occur

11. Kinetics Studies the rate at which a chemical process occurs.
Besides information about the speed at which reactions occur, kinetics also sheds light on the reaction mechanism (exactly how the reaction occurs).

12. Temperature and Rate
chemical reactions speed up when the T is increased
Ex. food spoilage / refrigerators

13. Temperature and Rate Why? increase in T means increase in KE
increase in KE means an increase in collisions
the reaction rate is much smaller than the collision rate because most collisions don’t result in a reaction

14. Energy Activation Energy (Ea) –
threshold energy that must be overcome for a reaction to occur
should come from the KE of molecules before the collision
it is converted to PE to break bonds and change the arrangement of atoms

15. Energy

16. Energy in exothermic reactions, products have lower PE than reactants
in endothermic reactions, products have more PE than reactants
the size of ∆E does not effect rate but Ea does

17. Energy
As the T is increased, more collisions have enough energy to react
#successful collisions = (total collisions) e-Ea/RT

18. Orientations…… ooooo fancy
the molecules must collide with certain positions for a reaction to occur
Arrhenius Equation
collision frequency
A = zp : frequency factor
steric factor- fraction of collisions with right orientation m x y b
used to compare two sets of T and k values for same reaction

19. Catalysis another way to speed up the reaction
instead of increasing KE, the catalyst lowers the Ea
is never consumed in the reaction so is not considered a reactant
catalyst creates a new pathway with a lower activation energy
more collisions have enough energy
Example: enzymes in the body

21. Comparing Two Theories
Atomic Theory
Everything made of particles
All atoms of an element are identical
Atoms are neither created nor destroyed
A specific compounds has the same ratio of atoms
Kinetic-Molecular Theory
Particles have mass
Particles are constantly moving
Particles collide
Particles exert forces
Temperature measures kinetic energy

22. Laws of Thermodynamics
There are three laws
A fourth law does exist but it is called the zeroth law
You must understand the pieces of Gibbs free energy before you can see the laws

23. Gibbs Free Energy Changes
Very key equation:
This equation shows how G changes with temperature.
(We assume S° & H° are independent of T.)

24. Free Energy and Temperature
There are two parts to the free energy equation:
H— the enthalpy term, means heat
S — the entropy term, means chaos or randomness
The temperature dependence of free energy comes from the entropy term.

25. Entropy
Entropy (S) is a term coined by Rudolph Clausius in the 19th century.
Clausius was convinced of the significance of the ratio of heat delivered and the temperature at which it is delivered, q T

26. Free Energy and Temperature
By knowing the sign (+ or -) of S and H,
we can get the sign of G and determine if a reaction is spontaneous. Negative Gibbs free energy gives a spontaneous reaction

27. First Law of Thermodynamics
You will recall that energy cannot be created nor destroyed.
Therefore, the total energy of the universe is a constant.
Energy can, however, be converted from one form to another or transferred from a system to the surroundings or vice versa.

28. Second Law of Thermodynamics
The second law of thermodynamics: The entropy of the universe does not change for reversible processes and increases for spontaneous processes.
Reversible (ideal):
Irreversible (real, spontaneous):

29. Third Law of Thermodynamics
The entropy of a pure crystalline substance at absolute zero is 0.

30. Zeroth Law
The "zeroth law" states that if two systems are at the same time in thermal equilibrium with a third system, they are in thermal equilibrium with each other.