1. Reaction Energy
Exothermic reaction of Thermite

2. Review
Endothermic
Absorbs heat
Exothermic
Releases heat

3. Breaking and making Bonds
Energy is released when bonds are formed
It takes energy to break bonds
ENERGY
ENERGY

4. Energy and dissolving
When water molecules are attracted to the solute, energy is released.
Energy is absorbed when the water molecules separate ions that are attracted to each other.
ENERGY

5. Exothermic dissolving
More energy is released when water attracts to the solute than it takes to separate the solute.
Temperature increases

6. Endothermic dissolving
Less energy is released when water attracts to the solute than it takes to separate the solute.
Temperature decreases

7. Temperature vs Heat Temperature Heat
A measure of the average kinetic energy of the particles in a sample of matter
Heat
The energy transferred between samples of matter because of a difference in temperature
SI Unit = Joule

8. How can we determine how much ENERGY was transferred as heat during a temperature change?

9. Specific Heat Specific Heat (c)
The amount of energy required to raise the temperature of one gram of a substance by one degree Celsius (1°C) or one Kelvin (1K)
Units = joules per gram per degree Celsius
= J/(g·°C)

10. Specific Heat Notice the high specific heat of water Equation:
Keeps our atmosphere cool
Used in industry to cool machinery
Equation:
c = specific heat
Q = energy lost or gained as heat
m = mass
ΔT = temperature change = Tfinal – Tinitial

11. A 4.0 g sample of glass was heated from 274 K to 314 K and absorbed 32 J of energy as heat. What is the specific heat of this type of glass?

12. A 4.0 g sample of glass was heated from 274 K to 314 K and absorbed 32 J of energy as heat. How much energy will the same glass sample gain when it is heated from 314 K to 344 K?

13. A 500 mL sample of water was heated and the temperature increased from 20°C to 84°C. How much energy was transferred as heat to the water? specific heat of water = 4.18 J/(g·°C)