Aim: How can we describe forms of energy? Do Now: What are some of the signs that a chemical reaction has occurred?

Energy Every chemical change in a substance involves an energy change. When energy is released by the reaction, it is known as an exothermic reaction. When energy is absorbed by the reaction, it is known as an endothermic reaction.

BUT… What is energy? Energy is defined as - the ability to do work. Work is done on an object when the object responds to a force (push or pull) and is moved some distance. If the object does not move, NO work is done.

Different forms of energy Chemical Light Nuclear Heat Electromagnetic Mechanical (Potential and Kinetic) Etc…

Potential Energy Energy due to position OR stored energy. This energy is available to do work at a later time. Examples: A stretched rubber band. Water at the top of a water fall. A yo-yo held in your hand. A stretched bow.

Kinetic Energy The energy of motion. Examples: Shooting the rubber band. Water falling over the water fall. A yo-yo in motion. The bow being released.

What happens when… Potential energy is changed into kinetic energy? The energy is simply changed from one form to another. The law of conservation of energy states that energy cannot be created nor destroyed. So, whether it changes from potential to kinetic or, chemical to light or, chemical to mechanical , etc… it is still energy. Just a different form.

Where is the potential energy ? Where is the kinetic energy ?

What about water? Does boiling water have kinetic or potential energy? What is the difference in energy between frozen water, water in a glass, and boiling water? Each has differing amounts of potential energy and kinetic energy.

How do we measure energy? The SI unit (metric unit) for measuring energy is the joule. The joule is a measure of heat produced by work. Refer to Reference Table D. What does it tell you about the joule?

Activity

Homework # Read pages 87-92 (sections 5.1 through 5.5) Copy and answer: Page 89 #1,3,4,7 Page 92 #9,10,11