1. Chapter 6

2.  Temperature ◦ Is something hot or cold? ◦ Relative measure

3.  Temperature ◦ Molecules of all substances are in constant motion ◦ Depends on the kinetic energy of molecules in a substance

4.  Temperature ◦ Greater the temperature ◦ Greater the motion of its molecules ◦ Measure of the average kinetic energy of the molecules of a substance

5.  Thermometer ◦ Measuring instrument  Utilizes the physical properties of materials to accurately determine temperature ◦ Thermal expansion  Expand with increasing temperature  Contract with decreasing temperature

7.  Temperature scales ◦ Reference points ◦ Ice points  Freezing point of water ◦ Steam point  Boiling point of water

8.  Temperature scales ◦ Fahrenheit  Ice point 32   Steam point 212  ◦ Celsius  Ice point 0   Steam point 100 

9.  Temperature scales ◦ Kelvin  Absolute temperature scale  Zero temperature is the absolute lower limit  Absolute zero

11.  Heat ◦ Flows from higher to lower temperature ◦ Energy in transit because of a temperature difference ◦ When heat is added to a body, internal energy increases

12.  Heat ◦ SI unit Joule (J) ◦ Common unit calorie (cal)  Heat necessary to raise one gram of pure water by one Celsius degree

13.  Kilocalorie ◦ Food calorie (Cal) is equal to one kilocalorie

14.  British thermal unit (BTU) ◦ British system unit of heat ◦ Heat necessary to raise one pound of water one Fahrenheit degree

15.  Nearly all matter expands when heated and contracts when cooled  Water is an important exception ◦ Expands when frozen

17.  Specific heat ◦ Heat necessary to raise the temperature of one kilogram of a substance one Celsius degree ◦ Specific to a particular substance ◦ Greater the specific heat ◦ Greater its capacity for heat

19.  Recall: heat will flow from Hot to Cold  ie: from high heat content to low heat content  Until they reach thermal equilibrium Thermal Equilibrium  Heat energy lost = heat energy gained

20. hot substance cold substance

21. hot substance cold substance

22. hot substance cold substance

23. hot substance cold substance

46. (hot) (cold)

47. (hot) (cold)

48. (hot) (cold)

49. What’s going to happen to the temperature of the small block?

50. What’s going to happen to the temperature of the large block? What’s going to happen to the temperature of the small block?

66. (warm)

70. Heat is a form of energy that flows from one object to another (warm)

71. (always from hot to cold) (warm)

72.  Heat transfer occurs in mixtures too.  Consider mixing hot and cold water

73.  By mixing together, the energy from one is gained by the other.  The result is an increase in T for one and a decrease for the other

74. Heat gained = heat lost Heat gained Heat lost mc∆T = QQ= mc∆T mc∆T = mc∆T

75.  Practice  500. g of water at 35 ºC is added to 400. g of water at 85 ºC. What is the temperature of the resulting mixture once equilibrium has been reached?

76.  Phases of matter ◦ Solids ◦ Liquids ◦ Gases  Latent heat ◦ Heat associated with a phase change

77.  Latent heat of fusion ◦ Heat required to change solid into liquid

78.  Latent heat of vaporization ◦ Heat necessary to change a liquid into a gas

79.  Sublimation ◦ Changing directly from the solid to the gaseous phase  Deposition ◦ Changing directly from the gaseous to the solid phase

80.  Boiling ◦ Process by which energetic molecules escape from liquid ◦ Energy is gained from heating ◦ Increasing pressure increases the boiling point of water

81.  At mountain altitudes ◦ Decreased air pressure ◦ Boiling point of water lower that at sea level

82.  Evaporation ◦ Slow phase change of liquid to gas ◦ Major cooling mechanism  Evaporation of perspiration has a cooling effect  Energy is lost

83.  Evaporation ◦ Moving air promotes evaporation by carrying away water molecules ◦ Cooling effect

84.  Relative humidity ◦ Amount of moisture in the air ◦ Humid environment ◦ Little evaporation of perspiration ◦ Hot feeling

85.  Methods of heat transfer ◦ Conduction ◦ Convection ◦ Radiation

86.  Conduction ◦ Transfer of heat by molecular collisions ◦ Kinetic energy of molecules is transferred from one molecule

87.  Thermal conductivity ◦ Measure of a substance’s ability to conduct heat  Metals ◦ Good conductors  Liquids and gases ◦ Poor conductors ◦ Molecules farther apart ◦ Less collisions

88.  Convection ◦ Transfer of heat by the movement of a substance, or mass, from one position to another ◦ Movement of heated air or water

90.  Radiation ◦ Process of transferring energy by means of electromagnetic waves ◦ Dark colors absorb radiation better than light colors

92.  Three common phases of matter ◦ Solid ◦ Liquid ◦ Gas

93.  Solid ◦ Definite shape and volume ◦ Crystalline solid  Molecules arranged in a particular repeating pattern

94.  Heating ◦ Molecules gain kinetic energy ◦ Vibrate about their positions in the lattice ◦ Move farther apart ◦ Lattice becomes distorted

95.  Liquid ◦ Slight lattice structure ◦ Molecules relatively free to move ◦ Definite volume but no definite shape

96.  Liquid ◦ Individual molecules gain kinetic energy when heated ◦ Liquid expands as a result ◦ Gas phase  Occurs when molecules are completely free from each other

97.  Gas ◦ Rapidly-moving molecules ◦ Exert little or no force on another except when they collide

98.  Continued heating of a gas ◦ Molecules and atoms ripped apart by collisions with one another  Plasma ◦ Hot gas of electrically charged particles ◦ Ionosphere ◦ Lightning strikes ◦ Neon and fluorescent lamps

99.  Kinetic theory ◦ Pressure rises as temperature increases ◦ Gases diffuse in air

100.  Kinetic theory ◦ A gas consists of molecules moving independently in all directions at high speeds ◦ Higher the temperature, the higher the average speed

101.  Ideal gas ◦ Molecules are point particles (have no size at all) ◦ Interact only by collision  Collisions exert only a tiny force on the wall

102.  Pressure ◦ Force per unit area, p = F/A ◦ SI unit is N/m 2 or pascal (Pa)

103.  Pressure ◦ Directly proportional to number of gas molecules present ◦ Directly proportional to the Kelvin temperature ◦ Inversely proportional to volume

107.  The ideal gas law

108.  Thermodynamics ◦ Dynamics of heat  Production  Flow  Conversion to work

109.  Heat added to a closed system ◦ Internal energy ◦ Doing work

110.  First law of thermodynamics ◦ Positive heat values (heat is added to the system) ◦ Positive work values (work done by the system) ◦ Negative values indicate the opposite

111.  Heat engine ◦ Converts heat into work ◦ Some input energy is lost or wasted

112.  Second law of thermodynamics ◦ Impossible for heat to flow spontaneously from a colder body to a hotter body ◦ No heat engine operating in a cycle can convert thermal energy completely into work

113.  Third law of thermodynamics ◦ It is impossible to attain a temperature of absolute zero ◦ Would require all of the heat to be taken from an object

114.  Heat Pump ◦ Uses work input to transfer heat ◦ Low temperature to high temperature ◦ Reverse of a heat engine

115.  Entropy ◦ Does a process take place naturally? ◦ The entropy of an isolated system never decreases ◦ Measure of the disorder of a system

116.  Entropy ◦ Disorder increases as natural processes take place ◦ Total entropy of the universe increases in every natural process