LESSON How does energy change form? 19 Have you ever seen someone light a match? Before they light it, the match is cool. When it is lit, the match gives off light and. Where did this energy come from? There was chemical energy stored in the match. When the match was lit, the chemical energy changed into light and We call energy changes conversions [kun-vur-zhunz]. Conversion means a change into something else. Energy conversions are very important. You cannot live without them. The food you eat has chemical Your body converts (changes) this chemical energy to the energy and the energy you need to stay alive. Energy conversions are happening around you all the time. You flip up the switch in your home and the lights go on. Electrical energy has changed to light Your toaster converts electrical energy to A fan changes electrical energy to Its motor gets hot. You can also hear it. This means that some of the energy has changed to and When energy is converted from one form to another, the amount of energy you start out with is the amount of energy you end up with. Only the forms of energy change. We can put this idea in another way. o Energy cannot be made.. Energy cannot be destroyed. It is never "used up.". Energy can just change from one form to another. These three things are true for all kinds of Scientists call this idea the Law of Conservation [kahn-sur-vay-shun] of Energy. Conservation means saving. Although the energy changes its form, it is not lost. 110
&J ENERGY CONVERSIONS tl Figure A enerw. Mechanical enerry conaerts to Figure B Chemical energy cont:erts to and light ELECTRICAL ENERGY CONVERSIONS Electrical energy can be converted to: Figure C Light energy Figure D Heat energy Figure E Sound energy Figure F Mechanical energy 111
I TRY THIS AT HOME! What You Need (Materials) bowl thermometer eggbeater What to Do (Procedure) l. Fill a bowl with tap water. 2. Let it stand for several hours. Take the temperature of the water. Mix the water for two minutes with an eggbeater. Take the temperature of the water again. What You Saw (Observations) 1. The mixing made the water temperature Figure G rlse rise, drop 2. Mixing is an example of What You Learned (Conclusions) 8. This experiment shows that energy can be converted to MATCHING Match each term in Column A with its description in Column B. Write the correct letter in the spac proaided. Column A Colurnn B L. energy a) has stored energy wound-up spring b) has stored chemical energy conversions c) energy of moving things energy d) the ability to make things move battery e) energy changes L 112
L- WASTED ENERGY il Figure H A car takes the chemical energy in gasoline and converts it into the energy of its motion. However, not all the chemical energy of the gasoline converts to energy' In fact' only a small amount of the chemical "t't"t[y changls- into energy that moves the car' The rest is waste. Some of tn" frr"t-', "nergy is wasted"as,orrrr-d. Most of the energy is wasted as ' Some waste energy is always given off when energy changes from one form to another' Most waste energy is in the form of ' People who design cars try to make them waste as little energy as possible' These people are called engineers. Er,gineers ar" p"opt" who take scientific ideas and put them to practical uses' TRUE OR FALSE In the space proaided, write "true" if the sentence is true' Write "false" if the sentence is false' L. Heat is a form of energy. False False 2. 6. Heat is the only form of energy' Heat energy is sometimes useful' Heat energy is always useful' Energy can change from one form to another' Energy conversions always give off ' Heat energy can change to energy' Mechanical energy can change to energy' False 9. Energy changes are called conservations' 1.0. Energy changes are called conversions' 113
FILL IN THE BLANK Complete each statement using a term or terms from the list below. Write your answers in the spaces proaided. Some words may be used more than once. body electrical change light conversions move nuclear chemical 1. Energy is the ability to make something 2. The main forms of energy are electrical light, nuclear chemical and The energy of moving objects is called Energy "ur, change from one form to another. Energy changes are called converslons 7. Energy conversions take place inside your Food f,as chemibal energ'y. body 8. The body changes chemical energy to and 9. Motors sometimes give off wasted energy in the forms of energy and 10. The useful energy a motor gives is WRITE IT DOWN List the three parts of the "Laut of Conseraation of Energy." Start each part with the word "Energy." 1. 2. Energy cannot be made. Energy cannot be destroyed. Energy, can change from one form to another.