1. Applying the Law of Conservation of Energy Mrs. Paparella
Calorimetry
Applying the Law of Conservation of Energy
Mrs. Paparella

2. Law of Conservation of Energy
Energy can be neither created nor destroyed.
Heat naturally moves from warmer to colder objects or areas.
Energy is released by warmer objects and absorbed by colder objects.
Energy is measured in Joules (J) or Calories (Cal).

3. Temperature Heat and Temperature are NOT the same
Temperature is a measure of the average kinetic energy of molecules. (KE) Temperature is measured in Celsius (oC)
or Kelvin (K)
Cold objects have molecules with very little KE while hot objects have molecules moving much faster and have more KE.

4. Heat of Fusion Fusion means to melt.
Hf is the symbol for Heat of Fusion.
Ice has a specific heat of fusion: 334J/g
See Reference Table B.
The formula for calculating the amount of heat needed to melt ice is on Table T.
q=m Hf

5. How much heat is needed to melt 20 kg of ice?
Change 20kg to g.
20kg x 1000g = 2 x 104 g Kg
Find the formula q = m Hf
q= 2 x 104 g x 334 J/g
q = x 106 J

6. Is there a Change In Temperature?
When you have a temperature changed involved in a problem you have to use the formula: q=mcDT
See Table T (Heat)

7. How much heat is needed to heat water up to 100oC for a mug of cocoa using 250 ml of water that comes out of the tap at 20oC?
Need to use q=mcDT
Mass of water = 250 g since 1ml of water = 1 gram of water since density of water is 1 g/ml.
q = 250 g x 4.18 J/goC x (100oC-20oC)
q=?

8. How much heat is needed to boil a 4. 0 liter pot of water for pasta
How much heat is needed to boil a 4.0 liter pot of water for pasta? The water is at 30 oC already.
This is a 3 step problem.
First you need to bring the water up to the boiling point.
So use the formula: q=mcDT.
Then use the formula q= mHv
Hv stands for Heat of Vaporization and it means to boil the liquid at the boiling point.
Finally add the two answers together.