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2. Resources Bellringers Chapter Presentation Transparencies Standardized Test Prep Visual Concepts Math Skills

3. Heat and Temperature Chapter 13 Table of Contents Section 1 Temperature Section 2 Energy Transfer Section 3 Using Heat

4. Section 1 Temperature Chapter 13 Objectives • Define temperature in terms of the average kinetic energy of atoms or molecules. • Convert temperature readings between the Fahrenheit, Celsius, and Kelvin scales. • Recognize heat as a form of energy transfer.

5. Section 1 Temperature Chapter 13 Bellringer We use words like hot and cold, long and short, and heavy and light every day to describe the differences between things. In science, however, this is often not accurate enough and leads to confusion. • In drawing 1, which bowl would feel warm to your hands? Which bowl would feel cool?

6. Section 1 Temperature Chapter 13 Bellringer, continued • In drawing 2, which bowl would feel warm to your hands? Which would feel cool? 3. A person from Seattle tells his friend from Florida that the weather in Seattle is somewhat warm. When the friend arrives for a visit, he finds that he is uncomfortably cool wearing the shorts he packed. What would be a more effective way for the person from Seattle to explain the weather?

7. Section 1 Temperature Chapter 13 Temperature and Energy • Temperatureis a measure of how hot (or cold) something is. • Specifically, it is a measure of theaverage kinetic energyof the particles in an object. As the average kinetic energy of an object increases, its temperature will increase. • Athermometeris an instrument that measures and indicates temperature.

8. Section 1 Temperature Chapter 13 Measuring Temperature

9. Section 1 Temperature Chapter 13 Temperature and Energy, continued • FahrenheitandCelsiusare common scales used for measuring temperatures. • On theFahrenheitscale, water freezes at 32ºF and boils at 212ºF. • The Celsiusscale, which is widely used in science, gives a value of 0ºC to the freezing point of water and a value of 100ºC to the boiling point of water at standard atmospheric pressure.

10. Section 1 Temperature Chapter 13 Temperature and Energy, continued Fahrenheit-Celsius Conversion Equations A degree Celsius is 1.8 times as large as a degree Fahrenheit. Also, the temperature at which water freezes differs for the two scales by 32 degrees. TF = Fahrenheit temperature t = Celsius temperature

11. Section 1 Temperature Chapter 13 Temperature and Energy, continued Celsius-Kelvin Conversion Equation T = t + 237 T = Kelvin temperature t = Celsius temperature • TheKelvinscale is based on absolute zero. • Absolute zerois the temperature at which molecular energy is at a minimum (0 K on the Kelvin scale or –273.16ºC on the Celsius scale).

12. Section 1 Temperature Chapter 13 Temperature Scales

13. Section 1 Temperature Chapter 13 Math Skills Temperature Scale ConversionThe highest atmospheric temperature ever recorded on Earth was 57.8ºC. Express this temperature both in degrees Fahrenheit and in kelvins. • List the given and the unknown values. Given: t = 57.8ºC Unknown: TF = ?ºF T = ?K

14. Section 1 Temperature Chapter 13 Math Skills, continued 2. Write down the equations for temperature conversions. TF= 1.8t + 32.0 T = t + 273 • 3. Insert the known values into the equations, and solve. TF= (1.8  57.8) + 32.0 = 104 + 32.0 = 136ºF T = 57.8 + 273 = 331 K

15. Section 1 Temperature Chapter 13 Relating Temperature to Energy Transfer • Temperature changesindicate anenergy transfer. • Heatis the energy transferred between objects that are at different temperatures. • The transfer of energy as heat always takes place from a substance ata higher temperature to a substance at a lower temperature. • For example, if you hold a glass of ice water in your hands, energy will be transferred as heat from your hand to the glass.

16. Section 1 Temperature Chapter 13 Temperature and Heat

17. Section 2 Energy Transfer Chapter 13 Objectives • Investigate and demonstrate how energy is transferred by conduction, convection, and radiation. • Identify and distinguish between conductors and insulators. • Solve problems involving specific heat.

18. Section 2 Energy Transfer Chapter 13 Bellringer The three pictures all show examples of energy transfer. Answer the questions about what happens in each picture, and identify how the heat got from one object to another in each case. • Why is it a bad idea to drink hot cocoa out of a tin cup? Explain the energy transfers on the atomic level.

19. Section 2 Energy Transfer Chapter 13 Bellringer, continued 2. What happens to your hand when you place it above a lighted candle? (Assume you are not touching the flame. Explain the energy transfers on the atomic level. Hint: Remember that warm air rises.) 3. When you sit near a fire, you can feel its warmth on your skin, even if you are in cool air. Does this sensation depend upon the fact that warm air rises?

20. Section 2 Energy Transfer Chapter 13 Methods of Energy Transfer The transfer of heat energyfrom a hot object can occur in three ways: • Thermal conductionis the transfer of energy as heat through a material. • Convectionis the movement of matter due to differences in density that are caused by temperature variations. • Radiation is the energy that is transferred as electromagnetic waves, such as visible light and infrared waves.

21. Section 2 Energy Transfer Chapter 13 Methods of Energy Transfer, continued • Thermal Conduction • Conduction involves objects indirect contact. • Conduction takes place when two objects that are in contact are atunequal temperatures.

22. Section 2 Energy Transfer Chapter 13 Methods of Energy Transfer, continued • Convection • Convection results from the movement of warm fluids. • During convection, energy is carried away by a heated fluid that expands and rises above cooler, denser fluids. • Aconvection currentis the vertical movement of air currents due to temperature variations.

23. Section 2 Energy Transfer Chapter 13 Methods of Energy Transfer, continued • Radiation • Radiation is energy transferred as heat in the form ofelectromagnetic waves. • Unlike conduction and convection, radiation does not involve the movement of matter. • Radiation is therefore the only method of energy transfer that can take place in a vacuum. • Much of the energy we receive from the sun is transferred by radiation.

24. Section 2 Energy Transfer Chapter 13 Comparing Convection, Conduction, and Radiation

25. Section 2 Energy Transfer Chapter 13 Conductors and Insulators • Any material through which energy can be easily transferred as heat is called aconductor. • Poor conductors are calledinsulators. • Gases are extremely poor conductors. • Liquids are also poor conductors. • Some solids, such as rubber and wood, are good insulators. • Most metals are good conductors.

26. Section 2 Energy Transfer Chapter 13 Specific Heat • Specific heatdescribeshow much energyis required toraise an object’s temperature. • Specific heatis defined as the quantity of heat required to raise a unit mass of homogenous material 1 K or 1°C in a specified way given constant pressure and volume. Specific Heat Equation energy = (specific heat)  (mass)  (temperature change) energy = cmDt

27. Section 2 Energy Transfer Chapter 13 Math Skills Specific HeatHow much energy must be transferred as heat to the 420 kg of water in a bathtub in order to raise the water’s temperature from 25°C to 37°C? 1.List the given and the unknown values. Given:Dt = 37ºC – 25ºC = D12ºC = D12 K DT = 12 K m = 420 kg c = 4186 J/kg• K (from table in textbook) Unknown: energy = ? J

28. Section 2 Energy Transfer Chapter 13 Math Skills, continued 2. Write down the specific heat equation. energy = cmDt 3. Substitute the specific heat, mass, and temperature change values, and solve.

29. Section 3 Using Heat Chapter 13 Objectives • Describethe concepts of different heating and cooling systems. • Comparedifferent heating and cooling systems in terms of their transfer of usable energy. • Explain how a heat engine uses heat energy to do work.

30. Section 3 Using Heat Chapter 13 Bellringer One extremely cold winter day, the thermostat in the science classroom was set too low and the room was cold. The science teacher did not have the right tool to reset the thermostat, so she made a thin cloth cover for the thermostat, wet it, and placed it over the thermostat. Soon the room was comfortably warm. • You have learned that there is an energy change when a liquid evaporates. Will the area near the liquid get hotter or cooler as evaporation occurs? (Hint: Compare and contrast the molecular motion of particles as liquids and as gases.)

31. Section 3 Using Heat Chapter 13 Bellringer, continued • The thermostat is designed to turn the heater on when the temperature of the room falls below a certain temperature. How did putting the wet cloth over the thermostat turn the heater on so the room would get warmer?

32. Section 3 Using Heat Chapter 13 Bellringer, continued • Imagine a different situation in the same class, during the week before summer vacation. This time, it is very hot outside, but the thermostat is set so high that the air conditioner does not come on. Which of the following might help the thermostat trigger the air conditioner more frequently? a. use another wet cloth on the thermostat b. point a fan at the thermostat c. wrap the thermostat in a dark cloth that has been sitting by the windowsill d. wrap the thermostat in a dark cloth that has been kept in the refrigerator e. redirect air from the air conditioner vent away from the thermostat

33. Section 3 Using Heat Chapter 13 Heating and Cooling • Heating a house in the winter, cooling an office building in the summer, or preserving food throughout the year is possible because ofmachines that transfer energy as heatfrom one place to another. • These machines operate with two principles about energy that you have already studied: • Thefirst law of thermodynamicsstates that the total energy used in any process—whether that energy is transferred as a result of work, heat, or both—is conserved. • Thesecond law of thermodynamicsstates that the energy transferred as heat always moves from an object at a higher temperature to an object at a lower temperature.

34. Section 3 Using Heat Chapter 13 Air Conditioner One example is an air conditioner. An air conditioner does work to remove energy as heat from the warm air inside a room and then transfers the energy to the warmer air outside the room.

35. Section 3 Using Heat Chapter 13 Heating Systems Most heating systems use asource of energytoraise the temperatureof a substance such as air or water. • Thehuman bodyis a heating system. Some of the energy from food is transferred as heat to blood moving throughout the human body to maintain a temperature of about 37°C (98.6°F). • Incentral heating systems,heated water or air transfers energy as heat. • Solar heating systemsalso use warmed air or water.

36. Section 3 Using Heat Chapter 13 Heating Systems, continued • In the solar system shown here, asolar collectoruses panels to gather energy radiated by the sun. • This energy is used toheat waterthat is then moved throughout the house. • This is anactivesolar heating systembecause it uses energy from another source, such as electricity, to move the heated water.

37. Section 3 Using Heat Chapter 13 Heating Systems, continued • In apassive solar heating system, energy transfer is accomplished by radiation and convection. • In this example, energy from sunlight is absorbed in a rooftop panel. • Pipes carry the hot fluid that exchanges heat energy with the air in each room.

38. Section 3 Using Heat Chapter 13 Heating Systems

39. Section 3 Using Heat Chapter 13 Heating Systems, continued • When energy can be easily transformed and transferred to accomplish a task, such as heating a room, we say that the energy is in ausableform. • After this transfer, the same amount of energy is present, according to the law of conservation of energy. Yet less of it is in a form that can be used. • In general,the amount of usable energy always decreaseswhenever energy is transferred or transformed. • Insulationminimizes undesirable energy transfers.

40. Section 3 Using Heat Chapter 13 Cooling Systems • In allcooling systems,energy is transferred as heat from one substance to another, leaving the first substance with less energy and thus a lower temperature. • Arefrigerant is a material used to cool an area or an object to a temperature that is lower than the temperature of the environment. During each operating cycle, the refrigerant evaporates into a gas and then condenses back into a liquid.

41. Section 3 Using Heat Chapter 13 Refrigeration

42. Section 3 Using Heat Chapter 13 Heat Engines • Aheat engineis a machine that transforms heat into mechanical energy, or work. • Internal combustion engines burn fuel inside the engine. • An automobile engine is afour-stroke engine,because four strokes take place for each cycle of the piston. • The four strokes are calledintake, compression, power, andexhauststrokes. • Internal combustion engines vary in number of pistons.

43. Section 3 Using Heat Chapter 13 Internal Combustion Engine

44. Section 3 Using Heat Chapter 13 Concept Mapping

45. Standardized Test Prep Chapter 13 Understanding Concepts 1. What happens to the energy that is lost when an engine is less than 100% efficient? A. It is destroyed during combustion. B. It is converted to heat and transferred to the environment. C. It is converted to matter in the form of gases that enter the atmosphere. D. It is lost as friction between the tires of the vehicle and the surface of the road.

46. Standardized Test Prep Chapter 13 Understanding Concepts 1. What happens to the energy that is lost when an engine is less than 100% efficient? A. It is destroyed during combustion. B. It is converted to heat and transferred to the environment. C. It is converted to matter in the form of gases that enter the atmosphere. D. It is lost as friction between the tires ofthe vehicle and the surface of the road.

47. Standardized Test Prep Chapter 13 Understanding Concepts, continued 2. What change occurs in matter when its temperature is increased? F. The specific heat of the material increases. G. Atoms and molecules in the material move faster. H. The attraction between atoms and molecules increases. I. The frequency of collisions between atoms and molecules decreases.

48. Standardized Test Prep Chapter 13 Understanding Concepts, continued 2. What change occurs in matter when its temperature is increased? F. The specific heat of the material increases. G. Atoms and molecules in the material move faster. H. The attraction between atoms and molecules increases. I. The frequency of collisions between atoms and molecules decreases.

49. Standardized Test Prep Chapter 13 Understanding Concepts, continued 3. What transfer method carries energy from the sun to Earth? A. conduction B. convection C. insulation D. radiation

50. Standardized Test Prep Chapter 13 Understanding Concepts, continued 3. What transfer method carries energy from the sun to Earth? A. conduction B. convection C. insulation D. radiation