2. Energy

3. Copyright © 2007 Pearson Benjamin Cummings. All rights reserved. (a) Radiant energy(b) Thermal energy (c) Chemical energy(d) Nuclear energy(e) Electrical energy

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

5. Energy Kinetic Energy – energy of motion KE = ½ m v 2 Potential Energy – stored energy Batteries (chemical potential energy) Spring in a watch (mechanical potential energy) Water trapped above a dam (gravitational potential energy) massvelocity (speed) B A C

6. 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 KE = ½ m v 2 BUSBULLET 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

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

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

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