Chapter 9 Forms of Energy

Transcription

1 Chapter 9 Forms of Energy 9.1 What is energy? Energy is the ability to make things move. It is all around us but sometimes we don t recognize it. In order to properly describe energy, we classify it according to one of Ten Energy Forms. light energy energy which we can see. This is further categorized as either natural (sun) or artificial (electrically produced). gravitational energy of a falling body due to earth s gravitational field. e.g. roller coaster. thermal heat energy due to the movement of atoms or molecules. e.g. hair dryer. 1

2 magnetic energy due to the attractive or repulsive forces between certain types of metals (iron, nickel, cobalt and gadolinium) nuclear energy stored within the nucleus of an atom. e.g. when uranium nuclei split, they give off tremendous amounts of heat. This heat is used to produce electricity. electrical energy due to the movement of electrons in a conductor. e.g. any electrical appliance. 2

3 sound - energy due to vibrations in the air or other materials. mechanical energy in a set of moving of moving parts. e.g. egg beater. We also attribute bodies in motion to having mechanical motion, even if they do not have mechanically moving parts! chemical energy stored in the high-energy chemical bonds of molecules. When they undergo a chemical reaction, these bonds are broken and new, lower energy bonds are formed. e.g. gasoline or food. Activity 9b Review Energy transformations 3

4 energy transformation when energy changes from one form to another. This is very important because the only time you can make energy do work for you is when you transform it. input energy the start energy form. output energy the finish energy form. energy source the substance or object that provided the input energy. Input energy Output energy Demo example1: Magnet and paper clip. What is the energy transformation? Demo example2: Dropped basketball. What is the energy transformation? 4

5 Potential and Kinetic Energy Just when you thought you understood energy classification another way of classifying shows up. All energy can be classified as either kinetic energy (KE) this is the energy of motion or action. If something is moving, it has KE. The faster it is moving, the more KE it has. Be careful! Things like chemical, heat, light, sound and electricity are moving particles (WHEN THEY ARE IN USE)!!! potential energy (PE) this is stored energy. Energy can be stored by virtue of its gravitational position (how high it is and how far it can fall) or inside it s molecular bonds (like in gasoline). The PE/KE Roller Coaster of Science 5

6 PE KE PE KE PE KE The PE/KE Chemical Energy Graph of Science 6

7 Review Energy from the sun Although we tend to think that the sun just provides us with light so we can see things and heat to keep us warm, almost ALL the energy we use originates with the sun! Photosynthesis The most obvious third contribution of the sun is to provide energy to run the photosynthetic machinery of plants. Through photosynthesis, plants have the ability to trap light energy in the suns rays and to transform it into chemical energy, in the form of glucose (a simple sugar). This glucose is transformed into different other chemicals and is passed up the food chain, providing life for all living things. Without photosynthesis, only certain kinds of bacteria could survive on earth! Basic photosynthesis: carbon dioxide + water + light energy glucose (chemical energy) + oxygen 7

8 CO 2 + H 2 O + ην C 6 H 12 O 6 + O 2 When plants and trees grow, they store their chemical energy, if we eat a plant the stored chemical energy is passed to us. If we cut down a tree and burn the wood, the energy is released as light and heat. If the wood is put under pressure and heat and is turned into coal, gas or oil, the energy remains stored until we burn it. Assignment: Explain how other energy transformations, contained in the handout list, originated with the sun. Hydroelectric Power In British Columbia, hydroelectric power is of great importance. Not only does most of the electricity we use come from this source, but we even sell some to the USA! This electricity is made by transforming the energy of falling water (gravity) into that of turning a 8

9 turbine (mechanical), which also turns a generator rotor (mechanical). The spinning generator causes electrons in copper coils to move (electrical). What does this form of electricity have to do with the sun? The sun evaporates water, which rises to form clouds and precipitation. This precipitation is the water at high elevations that we use to drive the turbines. No sun no evaporation no precipitation no electricity! 9

10 Other Sun Sources solar heat panels where water is heated and circulated through a building to produce heat and hot water. 10

11 photovoltaic cells where sunlight is trapped and directly transformed into electricity. (anyone who has used a solar powered calculator has already experienced this!) Review 9.3 Chapter Review 11