1. Heat and Specific Heat Capacity Notes
CP Chemistry
Chapter 15

2. Energy Energy = ability to do work or produce heat
Heat = form of energy that flows from warmer to cooler object
James Joule was first person to connect energy and heat
Joule (J) = metric unit of heat and energy
takes joules to move 1 kg mass a distance of 1 meter in 1 second

3. Types of Energy Potential Energy Kinetic Energy energy of position
stored in chemical bonds
determined by type and number of chemical bonds
Kinetic Energy
energy of motion
formed when chemical bonds are broken

4. Law of Conservation of Energy
Energy is never created nor destroyed but it can change forms
Energy is usually lost in the form of heat
Example: car engines convert about 37% of energy into movement
feel the top of the hood after driving
most energy is lost as heat

5. Measuring Heat
Calorie = amount of heat needed to raise the temperature of 1 gram of pure water by 1oC
Food calorie = 1000 calories (or 1 kilocalorie)
Memorize the following conversions:
1 Calorie = 1000 calories = 1 kilocalorie
4.184 joules = 1 calorie
1000 joules = 1 kilojoule

6. How to Solve Heat Problems
Use Dimensional Analysis (factor-label method)
Set up all ratios with units NOT numbers
Plug in numbers
Multiply everything on top of fractions
Multiply everything on the bottom of fractions
Divide two numbers to get final answer

7. Heat Problems Examples
Convert 10 calories to joules
Convert 10 joules to calories
Convert 3000 calories to Calories
Convert 10 Calories to kilojoules

8. Specific Heat Capacity
Specific Heat = heat required to raise 1 gram of a substance by 1 oC
Every substance has its own specific heat because it has a different arrangement of atoms
Substance
Specific Heat
(J/goC)
Water
4.18
Aluminum
0.897
Gold
0.129
Ethanol
2.44

9. Specific Heat Equation
q = C x m x T
q = heat (J)
C = specific heat capacity (J/goC)
m = mass (g)
T = change in temperature (oC)
T = Final temperature – Initial temperature

10. Specific Heat Problem #1
If the temperature of 34.3 g of ethanol increases from 25 oC to 78.8 oC, how much heat has been absorbed by the ethanol? The specific heat for ethanol is 2.44 J/goC.

11. Specific Heat Problem #2
A 155 g sample of an unknown substance was heated from 25 oC to 40 oC. In the process, the substance absorbed 5696 J of energy. What is the specific heat of the substance?

12. Specific Heat Problem #3
What is the mass of a substance that has a specific heat of J/goC and has its temperature in a calorimeter raised from 20 oC to 90 oC when it releases 12,300 J of energy?