1. Forms of energy (a) Radiant energy (b) Thermal energy
1. Radiant — energy in light, microwaves, and radio waves
2. Thermal — results from atomic and molecular motion
– Temperature of an object is a measure of the thermal energy content
3. Chemical — results from the particular arrangement of atoms in a chemical compound; heat and light produced in this reaction due to energy released during the breaking and reforming of chemical bonds
4. Nuclear — released when particles in the nucleus of the atoms are rearranged
5. Electrical — due to the flow of electrically charged particles
(c) Chemical energy
(d) Nuclear energy
(e) Electrical energy
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

2. Potential energy kinetic energy kinetic energy Energy in Energy out
The energy something possesses due to its motion, depending on mass and velocity.

3. Energy KE = ½ m v 2 Kinetic Energy – energy of motionA C B
Kinetic Energy – energy of motion
KE = ½ m v 2
mass
velocity (speed)
Potential energy
– Energy stored in an object because of the relative positions or orientations of its components
Kinetic energy
– Energy due to the motion of an object
Kinetic energy, KE, of an object is related to its mass, m, and velocity v:
KE = ½ mv2
Potential energy is equivalent to work:
PE = Fd = mad = mgh
m = mass, g = gravity (9.81 m/s2) and h = height
Potential Energy – stored energy
Batteries (chemical potential energy)
Spring in a watch (mechanical potential energy)
Water trapped above a dam (gravitational potential energy)

4. School Bus or Bullet? Which has more kinetic energy;
a slow moving school bus or a fast moving bullet?
Recall: KE = ½ m v 2
BUS BULLET
KE = ½ m v 2
KE = ½ m v 2
Work
– One definition of energy is the capacity to do work.
– Easiest form of work to visualize is mechanical work, which is the energy required to move an object a distance d when opposed by a force F:
work = force  distance or w = Fd
– Because F, the force that opposes the action, is equal to the mass of the object times its acceleration, the preceding equation becomes
work = mass  acceleration  distance or
w = mad.
KE(bus) = ½ (10,000 lbs) (0.5 mph)2
KE(bullet) = ½ (0.002 lbs) (240 mph)2
Either may have more KE, it depends on the mass of the bus and the velocity
of the bullet.
Which is a more important factor: mass or velocity? Why?
(Velocity)2

5. Kinetic Energy and Reaction Rate
lower temperature
higher temperature
minimum energy
for reaction
Fractions of particles
Kinetic energy

6. Kinetic Energy and Reaction Rate
lower temperature
higher temperature
minimum energy
for reaction
Fractions of particles
Kinetic energy

7. Hot vs. Cold Tea Low temperature (iced tea) Many molecules have an
intermediate kinetic energy
High temperature
(hot tea)
Few molecules have a
very high kinetic energy
Percent of molecules
Kinetic energy