1. Bellwork Wednesday
Write “A” if the change is endothermic and “B” if the change is exothermic.
Melting wax
Boiling ethanol
Burning paper
Freezing ice cream
Vaporizing acetone A A B B A

2. Specific Heat Capacity(C)- The amount of heat it takes to raise the temperature of 1 g of a substance 1oC. It can be calculated: C = q (cal or J)_____ [mass (g)][DT(oC)]

3. specific heat units = cal/goC or J/g0C A low specific heat is matter that loses or gains heat quickly (like the tiles on the space shuttle) A high specific heat is matter that loses or gains heat slowly (like water) Water has a uniquely high specific heat compared to other substances.

4. To calculate the heat energy required for a temperature change, use the following formula: q = (m)(C)(DT) q = heat energy either absorbed or released (J or cal) m = mass (g) C = specific heat of the object (cal/goC or J/goC) DT= change in temperature of object (oC) (specific heat table)

5. Ex. How much energy is required to heat an iron nail with a mass of 7
Ex. How much energy is required to heat an iron nail with a mass of 7.0 g from 25oC until it becomes red hot at 750oC?
q = mC T C Fe= 0.46J/goC T = = 725oC q = 7.0g(0.46J/goC) 725oC q = 2300 J

6. Ex. If 5750 J of energy are added to a 455 g piece of glass at 24
Ex. If 5750 J of energy are added to a 455 g piece of glass at 24.0oC, what is the final temperature of the glass?
q = mC T
C glass= 0.50J/goC
T = ?
5750J = 455g(0.50J/goC) T
T = 25oC
Tfinal = = 49oC

7. Ex. A 30. 0 g sample of an unknown metal is heated from 22. 0oC to 59
Ex. A 30.0 g sample of an unknown metal is heated from 22.0oC to 59.2oC. During the process, 1.00 kJ of energy is absorbed by the metal. What is the specific heat of the metal?
C = q/(m T) T = = 37.2oC C = 1000J/ (30.0g)(37.2oC) C = J/goC

8. q = mC T m = 294 g 3590 cal=m(1.00cal/goC)12.2oC
Ex. If it takes 3590 calories to heat up a sample of water by 12.2oC, what is the mass of the water?
q = mC T
3590 cal=m(1.00cal/goC)12.2oC
m = 294 g