1. Energy

2. Definition Energy is the ability to do work Work is done on an object whenever a force (push or pull) moves an object through a distance Work = Force x Distance

3. Forms of Energy Mechanical energy –any energy possessed by macroscopic (visible) objects Two kinds of mechanical energy Kinetic Energy Potential Energy

4. Stored energy that is available to do work at a later time

5. Kinetic Energy Energy of motion

6. Heat is a form of Kinetic Energy

7. Unit of Energy Joule (J) Unit used to be the calorie (cal) 1 cal = 4.19 J How many joules is 1500 calories? How many calories is 36 J?

8. Conservation of Energy Whatever changes occur in energy from one type to another, the total amount of energy remains constant Energy cannot be created or destroyed

10. Equivalence of Mass and Energy Einstein found that matter and energy are related Whenever there is a decrease in energy in a system, there is an increase in mass Whenever mass increases, energy decreases

11. New Conservation Law Old conservation of matter and energy laws were combined Law of Conservation of Mass and Energy – the total of mass and energy will remain constant in any reaction

12. Energy in Reactions In every change, there is a change in energy Energy change usually more noticeable in chemical changes

13. Exothermic If reactants have more chemical energy than the products, then energy must be lost in reaction This release in heat energy causes the substances to become hot Chemical reactions that release heat are called EXOTHERMIC

14. Endothermic Reactions If products have more chemical energy than reactants, energy must be absorbed The absorption of heat causes substances to feel cold This is called an ENDOTHERMIC reaction

15. Activation Energy Even though some reactions are exothermic it may still require a little energy to start it off This starting energy is called ACTIVATION ENERGY