What is Energy?
Energy:
• The ability to cause change;
capacity to perform work.
• Units:
• Joules
• Kilowatt-hours
• Calories or kilocalories
• Some types of energy:
• Kinetic
• Potential
• Gravitational
• Chemical
• Thermal (or heat)
• Electromagnetic
Sources of Energy
Forms of Energy
Forms of Energy
Forms of Energy Review
Energy Transformations
Energy Transformations
Energy Transformations
Thermal Energy
Thermal Energy
Temperature
• aka “heat”
• Definition: A
transfer of energy
• aka “hotness”
• Definition: Average kinetic energy
of particles in a substance.
that causes change
in temperature.
• Usually measured
• Measured in degrees
• Fahrenheit
• Celsius
in Joules
• Kelvin
Temperature Scales
Absolute Zero
•
•
Temperature at which
molecular motion
essentially stops.
Point at which no more
heat can be removed
from a system.
Boiling point
of water
212 F
100 C
373 K
Highest temp
ever recorded
in US
134 F
56.7 C
330 K
Freezing point
of water
32 F
0 C
273 K
0 F
-18 C
255 K
Moon, at its
coldest
-280 F
-173 C
100 K
Absolute
Zero
-460 F
-273 C
0K
Fahrenheit
Celsius
Kelvin
Heat in Reactions
Heat
Heat
Exothermic
•
•
•
•
Reaction that releases energy.
Reactants have more energy than products.
Energy must be released as products form.
Container will feel hot.
Heat
Endothermic
•
•
•
•
Reaction that absorbs energy.
Products have more energy than reactants.
Energy must be absorbed as products form.
Container will feel cold.
Heat
Heat Energy
Phase Changes & Energy
200
Temperature (°C)
Heat released
Steam
150
Boiling
100
50
Liquid Water
Melting
0
Heat absorbed
Ice
-50
0
200
400
600
800
1000
Heat (kJ)
1200
1400
1500
Heat Energy
Heat Energy