Aim How can we describe forms of energy
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: 1. A stretched rubber band. 2. Water at the top of a water fall. 3. A yo-yo held in your hand. 4. A stretched bow.
Kinetic Energy • The energy of motion. Examples: 1. Shooting the rubber band. 2. Water falling over the water fall. 3. A yo-yo in motion. 4. 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
- Slides: 12