1. Welcome to the MATH

2. Specific Heat Capacity- The amount of heat it takes to raise the temperature of 1 gram of a substance by 1OC.
Abbreviated “C”
Water has a HUGE value, compared to other chemicals.

3. For water, C = 4.18 J/(gOC)
This means, for water:
It takes a long time to heat up, and
It takes a long time to cool off.
Water is used as a coolant!

4. To calculate, use the formula:
q = m x C x ΔT
Heat is abbreviated as “q” and the units are Joules.
m = mass in grams
ΔT = change in temperature, calculated as Tfinal – Tinitial
C = specific heat units are in J/gOC

5. Heating Curve

6. The flat areas of the graph represent phase changes.
The formula for the heat in a phase change involves a concept called enthalpy.

7. The sign
Heat values can have a + value or – value.
How can I tell?

8. The sign
You must consider the system and the surroundings.
The system is what you are studying, the surroundings is the rest of the universe.

9. The sign
The System

10. The System The sign Heat will be +, if it is moving into the system.
(Temperature is rising)
The System

11. The System The sign Heat will be -, if it is moving out of the system.
(Temperature is dropping)
The System

12. Heat in phase changes
q = m x ΔH
q = heat (in Joules)
m = mass (in grams)
ΔH = enthalpy (in J/g). This is a constant to be looked up in a chart.

13. Heat in phase changes
ΔHfus = enthalpy of fusion, used when melting.
ΔHvap = enthalpy of vaporization, used when boiling.

14. Calculating Heat
How much heat is needed to raise the temperature of grams of liquid water from 13.5 oC to 75.0 oC?
The specific heat of water is 4.18 J/g oC.

15. Calculating Heat
How much heat is needed to melt grams of ice?
ΔHfus = 334 J/g

16. Review
How much heat is needed to raise the temperature of 75.0 grams of liquid water from 25.0 oC to oC?
How much heat is needed to boil it?

17. Calorimetry
Involves using an insulated container and water to find the heat lost by a hot object.
Uses the conservation of energy.

18. Calorimetry
The System

19. Calorimetry
Heatloss = Heatgain
So the heat lost by a hot object placed in water is equal to the heat gained by the water.

20. Calorimetry
Heatloss = Heatgain
m x C x ΔT = m x C x ΔT
hot object water
Hot side gets a negative sign!!
Final temperature is the same for both objects.

21. Let’s try one
If a piece of iron with a mass of 23.5 grams and a temp. of 455 oC is dropped into grams of water at 25.0 oC, what is the final temperature of the system?
C of iron = J/g oC
C of water = 4.18 J/g oC

22. You try one
If a piece of iron with a mass of 46.5 grams and a temp. of 100 oC is dropped into grams of water at 25.0 oC, what is the final temperature of the system?
C of iron = J/g oC
C of water = 4.18 J/g oC

23. You try one # 2
A piece of an unknown metal with a mass of 75.5 grams and a temp. of 255oC is dropped into grams of water at 25.0 oC. If the final temperature of the system is 27.9oC, find the C of the metal.
C of water = 4.18 J/g oC

24. Review
If a piece of lead with a mass of 93.7 grams and a temp. of oC is dropped into grams of water at 22.4 oC, what is the final temperature of the system?
C of Pb = J/g oC
C of water = 4.18 J/g oC

25. Review
A chunk of iron is heated from 25.0oC to 1536oC. If the mass is 5.75 grams, how much heat is transferred?
How much heat is needed to melt our 5.75 gram piece of iron?
C of iron = J/g oC
ΔHfus for iron = 13.8 kJ/mol

26. Review
How much heat is needed to melt our 5.75 gram piece of iron?
ΔHfus for iron = 13.8 kJ/mol

27. Review
A piece of Aluminum metal with a mass of 25.0 grams and a temp. of 475oC is dropped into 75.0 grams of water at 22.5 oC. What is the final temperature of the system?
C of water = 4.18 J/g oC
C of aluminum = J/g oC