1. Thermal Energy Chapter 16 1

2. THERMAL ENERGY & MATTER Work and Heat- work is never 100% efficient. Some is always lost to heat.

3. Heat- the transfer of thermal energy from one object to another because of a temperature difference. In what direction does heat flow spontaneously? FROM HOT to COLD

4. Temperature = measure of how hot or cold something is compared to a reference point. Temperature is the average kinetic energy of the particles in an object. In the image below, where is average kinetic energy greater? Higher temperature  

5. Heat flows DOWN the bar through COLLISIONS. Collisions transfer thermal energy from hot to cold.

6. Thermal energy- total potential and kinetic energy in an object. It depends on mass, temperature, and phase of an object. If both objects are in the same phase & at the same temperature, which one has MORE thermal energy?  Because there are MORE particles moving around.

7. Thermal expansion/contraction - change in volume of a material due to temperature change. Occurs because particles of matter collide more or less as temperature changes. Thermal expansion   Also, wrap on beaker and lava lamp

8. Specific Heat – amount of heat needed to raise ONE gram of a material ONE degree Celsius.

9. The LOWER a material’s specific heat the MORE its temperature rises when energy is added. Which will heat faster (has the lower specific heat)? Water? Or Lead? YES! Specific heat of water = 4.18 J/g°CSpecific heat of lead = 0.46J/g°C

10. HEAT TRANSFER What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation? CONDUCTION – The transfer of thermal energy with no transfer of matter.

11. What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation? CONVECTION – The transfer of thermal energy when particles of a liquid or gas move from one place to another

12. CONVECTION – in the earth and sun

13. HEAT TRANSFER What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation? RADIATION – The transfer of thermal energy by waves moving through space. ALL OBJECTS radiate energy!

14. THERMODYNAMICS The study of conversions between thermal energy and other forms of energy.

15. THERMODYNAMICS First Law: Energy is Conserved

16. Thermal, Under Where? What is thermal energy? Thermal energy is the total kinetic energy of all particles in a substance. Thermal energy is measured in joules (J). Thermal Energy and Heat 16

17. What is the difference between thermal energy and temperature? Temperature is related to the average kinetic energy of particles. Thermal energy is the total kinetic energy of all the particles. For example, a glass of water can have the same temperature as a lake, but the lake has much more thermal energy because the lake contains many more water molecules. Thermal Energy and Heat 5) Temperature and total amount of particles determine the thermal energy of a substance.

18. Which has more thermal energy? Bowl of Soup Pot of Soup 18 Small balloon Large balloon Tiger House cat

19. Heat It Up! What is heat? Heat is the energy transferred from an object at a higher temperature to an object at a lower temperature. Energy in the form of heat always flows from hot to cold. Thermal Energy and Heat 19

20. Draw an arrow in the direction in which energy in the form of heat would flow. Object 1Direction of heat flow Object 2 Metal rodFire HatSnowman Ice cubeGlass of warm water 20 Previous slide 7) 8) Energy as heat is flowing from the girls’ warm bodies to the cold air

21. Heat It Up! Thermal Energy and Heat How is heat measured? Heat is measured in two ways. One way is the calorie (cal) One calorie is equal to the amount of energy needed to raise the temperature of 1 g of water by 1 °C. Heat is also measured in joules (J) because heat is a form of energy. One calorie is equal to 4.18 joules. 21

22. How is heat measured? In nutrition, 1 Calorie (with a capital C) is actually 1 kilocalorie, or 1,000 calories. To find out how many calories are in food, a sample of food is burned inside an instrument called a calorimeter. The change in temperature in the calorimeter is used to calculate how much energy is released from the food sample. Thermal Energy and Heat 22

23. How is heat related to thermal energy? Adding or removing heat from a substance will affect its temperature and thermal energy. Heat, however, is not the same as thermal energy and temperature. Thermal energy and temperature are properties of a substance. Heat is the energy involved when these properties change. Even though two materials might have the same temperature, their thermal energies might be different. Thermal energy depends on how many particles are present in the object. Copyright © Houghton Mifflin Harcourt Publishing Company Thermal Energy and Heat 23 9) Energy as heat will be transferred from the warmer object to the cooler object until both objects are at the same temperature

24. How can heat affect the state of an object? The state of a substance depends on the speed of its particles. Adding energy in the form of heat to a substance can result in a change of state. Removing energy in the form of heat from a substance can also result in a change of state. Thermal Energy and Heat 24 11) Add energy in the form of heat or subtract energy in the form of heat.

25. Have you ever needed to touch a very hot object? What did you use to touch it without burning yourself? Make a list……. Have you ever needed to protect yourself from being cold? What sorts of things did you use? Make a list….. What do these two lists have in common? 25

26. 26 Energy as heat can be transferred in three main ways: conduction, convection, and radiation.

27. Keep Your Cool What is conduction? Conduction is the transfer of energy as heat from one substance to another through direct contact. As long as two objects are in contact, conduction continues until the temperatures of the objects are equal. Thermal Energy and Heat 27

28. What is conduction? A conductor is a material that transfers heat very well. Metals are typically good conductors. Thermal Energy and Heat 28 An insulator is a material that is a poor conductor of heat. Wood, paper, and plastic foam are examples of good insulators.

29. Copyright © Houghton Mifflin Harcourt Publishing Company Thermal Energy and Heat 29 Flannel Shirt conductor insulator Iron skillet conductor insulator Copper pipe conductor insulator Oven Mitt conductor insulator

30. What is convection? When water is boiled, the water moves in roughly circular patterns because of convection. This motion is due to density differences that result from temperature differences. The motion is called a convection current. Thermal Energy and Heat 30 Convection is the transfer of energy as heat by the movement of a liquid or gas. Convection occurs when a cooler, denser mass of gas or liquid replaces a warmer, less dense mass of gas or liquid by pushing it upward.

31. Convection 31

32. What is radiation? Radiation is the transfer of energy by electromagnetic waves. Examples of EM waves: visible light, microwaves, infrared light When radiation is emitted from one object and then absorbed by another, the result is the transfer of heat. Radiation can travel through empty space. Thermal Energy and Heat 32

33. ExampleConduction, convection or radiation When you put some food in the microwave, it gets hot. conduction A heater on the first floor of the school makes the air on the second floor warm 33

34. 34 Heat is the transfer of Thermal energy by Conduction ConvectionRadiation

35. 35

36. Thermal Energy and Heat Practical Uses of Radiation Copyright © Houghton Mifflin Harcourt Publishing Company A solar cooker is a device that cooks food using mirrors that concentrate radiation from the sun. In parts of the world that are far from electricity and clean water, solar cookers are a cheap and portable way to sterilize water for drinking. Many people like to use solar cookers because they do not require any fuel and do not release harmful emissions. 36

37. PART 2 - USING HEAT External combustion – produces electricity at power plants. Water is heated by a fuel and the pressurized steam spins a turbine. http://www.eas.asu.edu/~holbert/eee463/coal.html

38. HEAT ENGINES External combustion – nuclear power plants.

39. USING HEAT Internal combustion – car engines. The fuel (gas) is compressed and ignited (lit) to drive a piston.

40. Internal combustion – car engines. Four-stroke engine.