Energy

1
Energy

• Kinetic energy energy of motion

2
Energy

• Potential energy stored energy
• 1. energy of position due to gravity

3
Energy

• Potential energy stored energy
• 2. energy stored in
• chemical bonds

4
Law of Conservation of Energy

• Energy can not be
• created or destroyed,
• only converted from
• one form to another.

5
When energy is RELEASED in a chemical reaction,
it is called.

• EXOTHERMIC

6
When energy is ABSORBED in a chemical reaction,
it is called.

• ENDOTHERMIC

7
Units of Energy

• Energy is measured in JOULES
• Also in calories or kilocalories (food)
• How many calories are in a kilocalorie?

8
Units of Energy

• How many calories in the hamburger?
• 420 kilocalories

9
What is temperature?

• A measure of the average kinetic energy of the
  particles in a sample of matter.
• All atoms are moving!
• High temperature moving faster

10
Once again

• TEMPERATURE
• AVERAGE KINETIC ENERGY

11
Temperature Scales

• Celcius
• water freezes water boils
  Zero degrees 100 degrees

12
Temperature Scales

• Kelvin 0 K absolute zero (-460 oF)
• all motion of particles stops!
• Water freezes _at_ 273 K
• Water boils _at_ 373 K
• Kelvin never goes below zero (no negative
  numbers!)

13
Temperature Scales

• Kelvin Celsius 273
• Celsius Kelvin 273
• If it is 32O Celsius, what temperature is it in
  Kelvin?
• If it is 100 Kelvin, what temperature is it in
  Celsius?

14
Temperature Scales

15
Standard Temperature

• 0 degrees Celsius
• 273 Kelvin
• (in Table A)

16
At what temperature does liquid nitrogen boil?

• 77 Kelvin
• -195 Celsius
• -320 Farenheit

17
What is Heat?

• Heat is the sum total of all the kinetic
  energy in a sample of matter.
• How is heat different from temperature???

18
Heat ? Temperature

• Both the water in the bath tub and in the cup are
  at 25 oC

Which contains more HEAT?
19
Heat Capacity

• The amount of energy (in JOULES) needed to raise
  the temperature of the sample by 1 oC
• Which water sample has a higher heat capacity?

20
Specific Heat Capacity

• The amount of energy (in JOULES) needed to raise
  the temperature of 1 gram of the sample by 1 oC
• Which water sample has a higher specific heat ?

21
Specific Heat

• Specific heat measures how easily something can
  absorb (or then lose) heat.
• LOW specific heat little energy for something
  to heat up.
• HIGH specific heat lots of energy to heat
  something up
• Every substance has its own unique specific heat
  value.

22
Specific Heat Capacity

• In your experience, which substance below has a
  higher specific heat capacity (takes more energy
  to heat it up?)