1. AIM
How do we solve problems related to heat when there is no change in temperature?
DO NOW –
How much heat does it take to raise a 100g sample of water 10 degrees?

2. Why phase changes
Heating a substance causes the temperature to increase
Heating causes particles to move faster and collide harder
Moves them further apart
Larger distances equals weakening the forces of attraction between them
When the forces of attraction are weak enough, the distance between the particles increases markedly and the phase changes

3. Phase Change
During a phase change the substance is gaining energy, but not gaining temperature
So at 0oC H2O(s) is given 1000J of heat and turns into 0oC H2O(l)

4. What it is called Adding Heat Solid ----> Liquid ________
Liquid ----> Gas
The reverse happens when a substance cools
Gas ----> Liquid
Liquid ----> Solid
Some odd ones between solid and gas
Solid ----> Gas
Gas ----> Solid

5. Graphic Organizer

6. Heat of Fusion Hf=The amount of heat needed to a solid into a liquid
For water the Hf=334 J/g
Q=(m)(Hf)
So how much heat does it take to change 200g of water from a solid to a liquid?

7. Answer
So how much heat?
Q=(m)(Hf)
Q=(200g)(334J/g)
Q=66,800J

8. Heat of Vaporization
Hv=The amount of heat needed to change a liquid into a gas
For water the Hv=2260 J/g
Q=(m)(Hv)
So how much heat does it take to change 200g of water from a liquid to a gas?

9. AIM How to solve all heat problems?
DO NOW- How much heat does it take to change 150g of ice into water?

10. Answer
Q= (m)(Hv)
Q= (200g)(2260 J/g)
Q= 452,000 J

11. Example Lets look at the example of one of the hand outs
This is called a heating/cooling curve
Specific heat capacity water J/goC
Specific heat capacity ice J/goC
Specific heat capacity water vapor J/goC
Hv=2260 J/g
Hf=334 J/g