1.  Define, in your own words, the following: 1. Temperature 2. Heat

2.  Mr. Szwast has meetings after school on the following days, and therefore will not be available:  Wednesday, February 3  Monday, February 8

3. Chapter 12

4.  What is the difference between a hot object and a cold object?  Temperature is a measure of the average kinetic energy of the particles of an object.  The molecules of a hot object are moving faster than their counterparts in a cold object.  Does not depend on the mass of the object.

6.  The kinetic energy of an object depends on the speed of the whole object.  The temperature of an object depends on the average speed of the individual particles that make up the object.  The thermal energy of an object depends on the temperature and the mass of the object.

7.  The SI unit of temperature is the Kelvin, represented by a capital K.  The Kelvin scale has no negative temperatures: 0 K is absolute zero. Nothing can be colder than 0 K  Temperatures can easily be converted between Celsius and Kelvin

8. 1) Convert to Kelvin a)25˚C (approximate room temperature) b)100.00˚C (boiling point of water) c)37˚C (average body temperature of a human) 2) Convert to Celsius a)2 K (Approximate temperature of interstellar space) b)700. K (Approximate temperature of the surface of Venus) c)300. K (A warm summer day)

9.  Energy that is transferred between objects is called heat.  Heat always flows from hotter objects to colder objects.  Heat is represented by a capital “Q”  The unit of heat, like all energy, is the Joule, J  Heat can be transferred in three ways: ◦ Conduction ◦ Convection ◦ Radiation

10.  Conduction is the transfer of thermal energy through collision of particles.  Conduction spreads thermal energy through an object.  Heat can also be conducted from one object to another object in direct contact. ◦ Hot electric stove to a pot

11.  The motion of a fluid (liquid or gas) caused by temperature differences is called convection.  The motion of the fluid transfers heat faster than conduction alone.

12.  Radiation is the transfer of energy by electromagnetic waves.  Radiation does not depend on the presence of matter.  The sun heats the earth through radiation

13. 1) Convert to Kelvin a)16˚C (Today’s predicted high temperature in San Diego) b)-3.3˚C (Last night’s low temperature in Punxsutawney, PA) c)1528˚C (The melting point of iron) d)5500˚C (Approximate temperature of the sun’s photosphere) e)1.5x10 7 ˚C (Approximate temperature of the sun’s core)

14.  Heat is transferred from a hotter object to a colder object.  This is done until the objects are at the same temperature.  Thermal equilibrium is reached when the objects have reached the same temperature.  At thermal equilibrium, the amount of heat from A  B equals the heat from B  A.  There is still heat transfer, but it is balanced, like balanced forces.

15.  The specific heat capacity of a material (in SI units) is the amount of heat needed to raise 1 kg of the material by 1 K.  Often called “specific heat” or “heat capacity”  The specific heat capacity of a material is measured in Joules per kilogram per Kelvin,  Specific heat is represented by “C”  Specific heats vary widely from one material to another

17.  The amount of heat transferred is equal to the mass of the object times the specific heat of the object times the difference between final and initial temperatures.  Since Celsius and Kelvin have the same temperature interval, you can use either for this equation (but not equations we’ll see later).

18.  A 5.00 kg cast iron skillet is heated on the stove from 300. K to 450. K. How much heat had to be transferred into the iron skillet?

19.  When you turn on the hot water to wash dishes, the water pipes absorb some of the heat from the hot water. What is the mass of the pipes if they are made of copper and absorb 100. kJ when the temperature is raised from 25˚C to 75˚C?

20.  Suppose you drink 0.20 kg of water at 20.˚C. Once inside your stomach, it absorbs heat until it reaches 37˚C. How much heat did the water absorb from your body?

21.  52500 J of heat are transferred into an 8.25 kg block of lead, raising its temperature to 340. K. What was its initial temperature?

22.  Read pages 313-318  Page 319 #3-5  Page 322 #10-13  Read pages 319-322

24.  750 kJ of heat are transferred from a stove to a 13 kg cast-iron pan. If its initial temperature is 21°C, what is its final temperature?

26.  A calorimeter is a device used to measure changes in thermal energy.  A calorimeter provides a closed, isolated system.  A simple calorimeter contains a hot test substance and a known mass of cold water.  More complex calorimeters are used to measure chemical reactions and energy content of food.

28.  Heat is transferred from the hot object to the cold object  No heat is lost; Any heat taken from the hot object must go to the cold object. ◦ (Technically, the calorimeter absorbs some of the heat, but we will often neglect it).

29.  A 25.0 g piece of copper at 175°C is dropped into a calorimeter containing 500. g of water at 25.0°C. What is the final temperature of the water?

30.  Read Section 12.1 (pages 313-322)  Page 321 #6-9  Page 336 #36-40, 52-60  Read Section 12.2 (pages 323-331)

33.  Solid, liquid, and gas are the most common states of matter  An exchange of heat is required to change the state of matter  Solid  Liquid  Gas requires heat flow into the object  Gas  Liquid  Solid requires heat flow out of the object  Changes of state of a pure substance occur at a constant temperature

34.  The melting point of a substance is the temperature at which it changes between a solid and a liquid. ◦ The same as the freezing point.  The boiling point of a substance is the temperature at which it changes between a liquid and a gas.

36.  A hot cup of coffee is left out on a counter. When it is put down, its temperature is 72˚C. When it is picked up 15 minutes later, its temperature is 51˚C. The mass of the coffee is 0.31 kg. Assume the specific heat capacity of coffee is the same as water. How much heat was transferred out of the coffee?  What mode(s) of heat transfer were responsible for the heat loss?

38.  The heat required to melt a solid is equal to the mass of the solid times the heat of fusion  The heat loss required to freeze a liquid is equal to the mass of the liquid times the heat of fusion.

39.  How much heat is required to melt 35 g of ice at 273 K? The heat of fusion of water is 3.34x10 5 J/kg.

40.  It takes 26.8 kJ to melt 425 g of gold at its melting point. What is the heat of fusion of gold?

42.  The heat required to vaporize a liquid is equal to the mass of the liquid times the heat of vaporization  The heat loss required to condense a gas is equal to the mass of the gas times the heat of vaporization

43.  A pot of water is boiling on the stove. How much heat is required to vaporize 725 g of water? The heat of vaporization of water is 2.26x10 6 J/kg.

44.  A sample of 25 grams of liquid methanol is heated to its boiling point. It takes 22 kJ more heat to vaporize the methanol. What is the heat of vaporization of methanol?

45.  3.5 kg of iron is heated to its melting point. How much additional heat would be required to melt the iron?  Data about iron:

48.  A 1.000 kg block of water ice is originally at -20.0°C. It is heated to its melting point (0.000°C), melted, heated to its boiling point (100.00°C), vaporized, and then heated to 140.0°C.  How much total heat did the water absorb?

50.  The change in thermal energy of an object is equal to the heat added to the object minus the work done by the object/system.  The work done by the system is equal in magnitue to the work done to the system, but in the opposite direction

51.  A heat engine is a device that is able to continuously convert thermal energy into mechanical energy (work)  Requires a high temperature (T H ) source of thermal energy (Q H ), called the input heat  Requires a low temperature (T L ) sink of thermal energy (Q L ), called the waste heat  Creates work based on heat in and out  An automobile internal combustion engine is one example of a heat engine

53.  A heat engine removes 825 J of thermal energy from a high temperature source and produces 421 J of work. How much waste heat is produced?

54.  A heat engine removes 737 J of thermal energy from a high temperature source and produces 583 J of waste heat. How much work does the engine produce?

55.  The efficiency of a heat engine is equal to the ratio of work done to input heat  Efficiency is a unitless number between zero and one,

56.  A refrigerator is the reverse of a heat engine  Requires an input of work to move thermal energy from a colder system to a warmer system.

57.  Entropy is the measure of disorder in a system.  Entropy is represented by a capital S  Entropy has units of Joules per Kelvin, J/K  The entropy of the universe is always increasing.  The change in entropy of an object/system is equal to the heat added to the object divided by the temperature of the object in Kelvins

58.  Entropy increases if: ◦ Heat is added ◦ Things get mixed together ◦ A solid melts ◦ A liquid evaporates ◦ Something breaks or spills  Entropy decreases if: ◦ Heat is removed ◦ Things get separated ◦ A gas condenses ◦ A liquid freezes ◦ Something is put in a more orderly form

59.  A beaker contains 150 g of water at 22˚C. The water is heated to 75˚C. How much heat must be added to the water to accomplish this?  Water data:

60.  The 2 nd Law of Themodynamics states the following:  Natural processes go in the direction that maintains or increases the total entropy.  Heat will never flow from a cold object to a hot object without external work.

61.  State whether each of the following processes causes entropy to increase or decrease: 1. Cleaning your room 2. Ice melting 3. Mixing cooking ingredients together 4. A baseball smashing a window

62.  State whether each of the following processes causes entropy to increase or decrease: 1. Hot lava turning to igneous rocks 2. Putting sugar and cream in coffee 3. Putting cluttered files away in a filing cabinet 4. Using a pile of Legos to build a miniature house

63.  Read Conceptual Physics Chapter 21 (pages 307-321)  Answer page 322 review questions #1-18  Homework: Page 336 #52-54, 61-63

64.  Read Chapter 12  Page 319 #3-5; Page 322 #10-13  Page 321 #6-9; Page 336 #36-40, 52-60  Page 325 #19-21; Page 328 #22-26  Page 336 #35, 41-44, 61-73  Chapter 12 Study Guide  Design a Lab (details coming soon)