1. Matter and Energy
When Matter and energy interact changes in matter occur.

2. Energy Definition: the ability to do work Is NOT matter
Is measured in the unit Joules (J)
Can be POTENTIAL or KINETIC

3. Potential Energy Energy that is stored
Something has the “potential” to do some kind of work
Example: the child at the top of the slide has potential energy

4. Kinetic Energy Energy of motion
Example: the child going down the slide now has kinetic energy

5. Different types of energy…
Light  is waves, visible or invisible
Electrical involves moving electrons
Heat movement of molecules
Chemical is contained in foods
Nuclear responsible for the sun
Sound waves/vibrations of molecules
Mechanical involves moving objects
Magnetic opposing poles

6. Law of Conservation of Energy
Energy, like matter, is neither created nor destroyed, rather it is converted.

7. Summary: What will we study in this unit?
What is heat? How is it different from temperature?
How does energy relate to chemical reactions?
How energy relates to phase changes?

8. Understanding Heat Flow
Heat (q) is defined as the energy that transfers from one object to another.
Heat flows from warm  cool.
What will happen if the two objects are touching?

9. Heat Energy vs. Temperature
Temperature is measure of the heat flow.
Temperature is a measure of the average kinetic energy of the particles in matter.

10. Heat Energy and Changes in Matter
In virtually all changes in matter, energy is released or absorbed.
System vs. Surroundings

11. Examples

12. Exothermic Reactions (Changes)
Exothermic reactions RELEASE ENERGY
Has a Negative q value.
Heat is a product.

13. Endothermic Reactions (Changes)
Endothermic reactions ABSORB ENERGY
Has a Positive q value because heat is entering the system.
Heat is a reactant.

14. Activation Energy Sometimes reactions can’t occur on their own
They need a little input of energy to get it started.
This energy is called ACTIVATION ENERGY.

15. Energy and Phase Changes
Energy of particles of matter relates to the phase or state of matter (solid, liquid, or gas)
Changes in energy then result in changes of matter.

16. Phase Changes Other terms Change in phase Endo or Exo Sign of ΔH or q
Melting
Liquefying
S  L
Endo +
Freezing
Solidifying
L S
Exo -
Vaporization
Boiling
L  G
Condensation
_______
G  L
Sublimation
S  G

17. Heating Curve of Water F D E C B A

18. What changes in phase are occurring…
AB- solid, ice
BC- melting
CD- liquid
DE- boiling
EF- gas

19. What changes in energy are occurring…
AB- increase in KE
BC- no change in KE, but still adding heat, so increase in PE
CD- increase in KE
DE- increase in PE
EF- increase in KE

20. What is specific heat capacity?
The amount of heat energy required to raise 1 unit of mass of a substance by 1 unit temperature.
C=4.18 J/g°C (specific heat capacity of water). Table B

21. Heat of Fusion
Heat of fusion (Hf) = amount of heat energy absorbed or released when melting or freezing.
See Reference Table B for values
Ex: Hf H2O = 334 J/g

22. Heat of Vaporization
Heat of vaporization = heat absorbed or released when vaporizing or condensing.
See Reference Tables for values.
Ex: HVH2O = 2260 J/g

23. Kinetic Theory of Heat
Molecules and atoms are constantly in motion, even in the SOLID phase.
They are said to have kinetic energy or the energy of motion.
As the energy of the particles increases, temperature increases.

24. Heat Calculations and Phase Changes
One can calculate how much heat is absorbed or released.

25. If the problem says… Potential energy Melt/freeze Vaporize condense
At 0°C (melting/freezing point)
At 100°C (boiling/condensing point)
Potential energy
Use
Q = mHf (melting/freezing) or
Q = mHv (vaporization/condensation)

26. If the problem says… Kinetic energy Temperature changes
Increase in temp from __ to __
Decrease in temp from __ to __
Heat a liquid/solid
Cool a liquid/solid
Kinetic energy
Use
Q = mCΔT

27. Examples How much heat is needed to melt 10.5 grams of ice at 0°C?
Use Q = mHf
Q = (10.5 g) (334 J/g)
Q= 3507 J

28. Examples
What mass of liquid water can be vaporized if 680 J of heat energy is added at 100°C?
Use Q = mHv
680 J = (m) (2260 J/g)
m= 0.30 g

29. Examples
How much energy is needed to increase the temperature of 5.0 grams of water from 0°C to 10°C?
Use Q = mCΔT
Q = (5.0 g) (4.18 J/g°C)(10-0)
Q= 209 J

30. Examples
What is the mass of water that can be increased in temperature by 15°C by the addition of 800 J?
Use Q = mCΔT
800 J = (m) (4.18 J/g°C)(15°C)
m= 12.8 g

31. Calorimetry
Used to measure amount of heat released or absorbed during a chemical/physical change that occurs in water solution.
“calorimeter” is used to measure the change in temperature of water surrounding a reaction.

32. Cheap Calorimeter- insulation