2. CHAPTER 4 ENERGY

3. Energy changes With all motion energy is required. When an object moves it has Kinetic energy (motion). When an object is standing still it has Potential energy. A burning match has Kinetic energy. The amount equals the Potential energy that was stored in the match before it was lighted.

4. A battery before it is used has Potential energy. Food setting on a shelf has Potential energy. Kinetic energy= Mass* velocity 2 2 Kinetic energy increases with an increase in mass and/or velocity.

5. Law of Conservation of energy Energy cannot be created or destroyed. Energy can change forms. Such as mechanical energy of a hand changing to electrical when it turns a hand generator. Or mechanical energy changing to sound energy in a speaker.

6. Energy Energy - The ability to cause changes. Forms of energy: Radiant Electrical Chemical Thermal Nuclear

8. Potential energy, energy of position or condition A special type of potential energy is called gravitational potential energy. G.P.E. - dependent upon the height above the earth’s surface

9. Conservation of Energy Energy can not be created or destroyed. Mechanical energy Total amount of kinetic and potential energy in a system.

10. http://science.howstuffworks.com/ roller-coaster2.htm

11. Work Define: The transfer of energy through motion. A force must be exerted through a distance in order for work to be done. Work = force x distance or W = F x d

12. Work Work is measured in joules. 1 joule equals a newton – meter (N m) Joule - amount of work done when a force of one newton acts through a distance of one meter. When 1 joule of work is done on an object, 1 joule of energy has been transferred to the object.

13. Work When describing work it is important to identify on what the work is being done. For work to be done, something must move and the movement is in the direction of the applied force.

14. Temperature and Heat Define: Measure of the average kinetic energy of matter

15. Temperature and Heat Matter is constantly moving, thus has kinetic energy Speed of the particles either increase or decrease Kinetic energy either increases or decreases Temperature must either increases or decreases

16. Thermal Energy The total energy of the particles in a material. Includes both kinetic and potential energy. Depends on the amount of material. Different for different types of materials.

17. Heat Define: The thermal energy that flows spontaneously from warmer to cooler materials. Measured in joules. Heat is a transfer of energy over a distance.

18. Measuring Thermal Energy Define: The amount of energy needed to change the temperature of one kilogram of a material by one degree Kelvin. Measured in units of joules per kilogram per degree Kelvin. J / (kg. K).

19. Measuring Thermal Energy Specific heat can also be thought of as the amount of energy absorbed or released by a kilogram of material for each degree of change in temperature. Each material has a unique specific heat.

20. Measuring Thermal Energy Change in thermal energy = mass x change in temperature x specific heat Q = m x  T x Cp  T = final temperature – initial temperature  T positive, the object has increased in temperature and gained heat.  T negative, the object has decreased in temperature and given off heat.

21. Heat capacity and Calories “c” (small c) one calorie= amount of heat needed to raise one gram of water 1°C. “C” (Capital C) One kilocalorie = food calorie

22. Calories 1 C (Capital C) food = 1000cal = 1 Kcal= 4184 joules So… 4.184 joules= 1 calorie (small “c”) S.I. Unit for heat = Joule Named for James Prescott Joule

23. Specific Heat: Amount of heat required to raise one gram of a substance 1°C. 50 °C 100°C 1 gallon water 1 cup of water What has a greater heat capacity? 1 gal. of water does…there is more of the water. So on a cold winter day a bowl of soup will warm you up better than a cup of coffee.

24. Problems Ex. 1 How many Calories are in 686,000 joules? =164 C 686000j(1 cal ) (1C (food) =163.9 4.184 j (1000 cal.)

25. Ex.2 How many joules are in 53.1 calories? 53.1cal. (4.184j) = 222.1 j = 1cal. 222 joules

26. Ex. 3 How many joules are in 9501 Calories? 9501C = (1000cal) ( 4.184j) (1Cal) (1cal.) =3.975*10 7 joules

27. Ex. 4 How many calories are in 95.77 joules? 95.77j(1cal./4.184j)= 22.889cal. = 22.89 cal.