# Specific heat capacity (a.k.a. Specific heat)

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Specific heat capacity (a.k.a. Specific heat)
3/27/2017 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

Answers 2. a) As calculated yesterday: 25.5 kJ
3/27/2017 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.

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.

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

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.

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

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 For more lessons, visit