Transcript Energy

Topic: Energy
Do Now:
1. Take out HW and open up
your notes from yesterday
All physical & chemical changes are
accompanied by change in energy
The chemistry of energy changes is
known as Thermochemistry!
Energy: Ability to do Work
The SI unit for an energy measurement
is called the Joule (J)
EXAMPLE: 1 Joule = amount of energy
required to lift a golf ball 1 meter

Other Energy Units:
calorie, Calorie, BTU’s

1 calorie = 4.18 Joules

1 Calorie = 1000 calories = 1 kilocalorie
There are 2 types of
energy (we are going to
draw another chart – like
the on we did for matter –
in our notebook
Energy
Non-mechanical – too
small to see
Mechanical – large
enough to see
Kinetic
Potential
Chemical
(Not a complete list!)
Heat
Light
Electrical
Nuclear
Kinetic Energy (KE) – makes things
move
• KE = ½ x Mass x Velocity2 = ½ mV2
• KE depends on how heavy and how fast
Potential Energy (PE): stored energy of
matter
• When Potential energy is released from
matter it becomes kinetic energy
Chemical Energy
• energy stored in bonds; it is released as
the result of a chemical reaction
Heat Energy
• Energy related to the changes in temperature
Light Energy – makes things visible
Electrical Energy – result of the flow of
electrons
Nuclear: energy is released by the change
in the nucleus of an atom (can be very
explosive)
Law of Conservation of Energy
• Energy is neither created nor destroyed in
ordinary chemical or physical change
Energy before = Energy after
Energy can be converted from one form to
another
- potential to kinetic - radiant to electric
- electric to heat
- chemical to kinetic
- chemical to electrical
Energy of Universe is conserved
Universe
EnvironmentEnvironment
System
Energy
Energy can
move between
the system
and the
environment
Two ways to classify chemical reaction:
1. energy (heat) is given off =
exothermic
2. energy (heat) is absorbed =
endothermic
Exothermic – releases heat to
environment
QUESTION: What happens to the temperature of
the environment?
QUESTION: What happens to temperature of
system?
a
EXO - energy leaves system (exits)
Temperature of
environment 
Environment
Temperature of
system 
System
Energy
Endothermic – heat is absorbed by the
system
QUESTION: What happens to the temperature of
the environment?
QUESTION: What happens to temperature of
system?
Endo - Energy enters system (enter)
Temperature of
environment 
Environment
System
Energy
Temperature of
system 
• Note: Heat flows from hotter object
to cooler object
• Example; Cold pack on leg: Heat
flows from the leg to the cold pack!
– Leg cools down; cold pack warms up