2. Specific heat capacity (a.k.a. Specific heat)
5/18/2019
Specific heat capacity (a.k.a. Specific heat)
symbolized as c, units in J/gC
It’s the heat required to raise 1 gram of a substance by 1 C
Heat capacity
calculated by c x m, units in J/C
It’s the heat required to raise the temperature of an object by 1 C.
Molar heat capacity
Similar to specific heat capacity, but uses moles instead of grams, units in J/mol C.
It’s the heat required to raise the temperature of 1 mol of a substance by 1 C

3. Answers 2. a) As calculated yesterday: 25.5 kJ
5/18/2019
Answers 2.
a) As calculated yesterday: 25.5 kJ
b) Specific heat is 4.18 J/gC (pg. 151)
c) Heat capacity: cm=4.18J/gCx200g=836 J/C
d) Molar heat capacity is c x g/mol
=4.18 J/gC x 18 g/mol = 75.3 J/molC
3. Simply using q=cmT,
c= 4.18 J/gC, m=335 g, T= = 1.9C
q=cmT= 4.18 J/gC x 335 g x 1.9C = 2.7 kJ
4. We cannot determine the c for wax from this data because we did not heat the candle (no value for T). We would have to change the lab procedure if we wanted c for wax.

4. q=cmT= 2.0 J/gC x 5 g x 60 C = 600 J
q=cmT,
c=q/mT= 10 J /(3.1 g)(17.9C) = 0.18 J/gC (gold is J/gC - pg. 151; it is not pure)
heat capacity = cm = 0.18 J/gC x 3.1 g
= J/ C
5.15: Something with a high c needs more energy to increase in temperature
5.16: Something with a low c experiences a greater rise in temp. given the same energy
5.18: The body is mostly water. Water (and the body) has a high c, thus a large change in energy will cause only a small shift in temp.

5. Crossword 8. negative 9. positive 11. grams 12. bomb
14. law of conservation of energy
17. insulator
18. endothermic
19. oxygen
20. water
1. enthalpy change
2. thermochemistry
3. calorimeter
4. heat of reaction
5. exothermic
6. out
7. surroundings
10. boundary
13. enthalpy
15. system
16. coffeecup

6. 9. Enthalpy (total energy) includes:
chemical potential energy of chemicals
gravitational potential energy
kinetic energy (earth’s rotation, etc)
heat energy
We cannot measure enthalpy because we cannot measure absolute gravitational or kinetic energy
10.Any reaction that produces light, sound, kinetic energy (explosion), etc.

7. 11.
Thermometer identifies T of water. H is found using q=cmT and law of conservation of energy (technically, pressure must be constant for q to equal H)
Boundary
Endothermic
Exothermic
System

8. A basic calorimeter - see handout
In our lab we tried to determine H via q from “calorimetry”. Here are some terms assoc-iated with calorimetry (and thermochemistry)
Endothermic = absorbing energy
Surroundings everything else
System with can as boundary
Exothermic = releasing energy
Law of conservation of energy = release and absorption of energy must be equal
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