© 2010 Pearson Education, Inc. Conceptual Physics 11 th Edition Chapter 15: TEMPERATURE, HEAT AND EXPANSION

© 2010 Pearson Education, Inc. Ch 15 This lecture will help you understand: Temperature vs Heat What is cold, really? Heat is not “contains” it is energy transfer and when that happens the internal energy increases or decreases. Internal energy (thermal energy) = KE+PE Q=mc T Thermal Expansion

© 2010 Pearson Education, Inc. Temperature

© 2010 Pearson Education, Inc. Thermal Expansion Thermal expansion Due to rise in temperature of a substance, molecules jiggle faster and move farther apart. Most substances expand when heated and contract when cooled. –Railroad tracks laid on winter days expand and can buckle in hot summer.

© 2010 Pearson Education, Inc. Thermal Expansion Thermal expansion (continued) Plays a role in construction and devices. Example: Use of reinforcing steel with the same rate of expansion as concrete—expansion joints on bridges. Gaps on concrete roadways and sidewalks allow for concrete expansion in the summer and contraction in the winter.

© 2010 Pearson Education, Inc. Figure 15.12

© 2010 Pearson Education, Inc. Figure 15.13

© 2010 Pearson Education, Inc. Projects- Ch 16 You and your group have been provided a topic in chapter 16 to research You will research your topic and present your topic using power point. You will be provided a set of guidelines for the power point and a rubric for the overall presentations. We will have Tuesday 1/5, Monday 1/11 and Tuesday 1/12 to research We will present on Friday 1/15 After presentations we will use the remaining time to review Ch 15. If we stick to 5 min per presentation we will have time to review. 5 min NO MORE…NO LESS

© 2010 Pearson Education, Inc. Topics 1.Conduction, Convection, Radiation 2.Greenhouse Effect 3.For Global Warming 4.Against Global Warming 5.Solar Power

© 2010 Pearson Education, Inc. PP Guidelines- read, read read and then read it again Slide 1: Names and Topic Slide 2: Definition Slide 3: Examples of your topic (5) Slide 4: Uses of your topic (5) Slide 5: Pictures (5 minimum) Slide 6: Name one thing that Christianity has brought to science Slide 7: Bibliography in correct format Each group is responsible for creating 2 test questions with answers. You will create these using word and MUST them to me by MONDAY 1/11. You are also responsible for determining the best way to have your presentation TO ME before the day you present. You cannot use a flash drive. So it or use an online storage system.

© 2010 Pearson Education, Inc. Rubric Area graded Speakers knew material and was easy to hear Missing oneNot at all Speakers stood tall during presentation Most of the timeSome of the timeNot at all Topic was defined Not at all 3-5 Examples 2 examples1 exampleNot at all 3-5 Uses 2 Uses1 UseNot at all 5 Pictures5 pictures4 pictures3 pictures2 picturesNot at all Proper Bibliography format Not at all CreativeVery CreativeCreativeNot very CreativeNot at all Handout provided Not at all 3 Test Questions Provided Not at all Project On time and Presentation within 5 min Missing oneNot at all

© 2010 Pearson Education, Inc. Ch 17

© 2010 Pearson Education, Inc. Evaporation Change of phase from liquid to gas

© 2010 Pearson Education, Inc. Evaporation Molecules in liquid move randomly at various speeds, continually colliding into one another. Some molecules gain kinetic energy while others lose kinetic energy during collision. Some energetic molecules escape from the liquid and become gas. Average kinetic energy of the remaining molecules in the liquid decreases, resulting in cooler water.

© 2010 Pearson Education, Inc. Evaporation Important in cooling our bodies when we overheat Sweat glands produce perspiration. Water on our skin absorbs body heat as evaporation cools the body. Helps to maintain a stable body temperature.

© 2010 Pearson Education, Inc. Condensation Condensation process Opposite of evaporation Warming process from a gas to a liquid Gas molecules near a liquid surface are attracted to the liquid They strike the surface with increased kinetic energy, becoming part of the liquid

© 2010 Pearson Education, Inc. Condensation Condensation process (continued) Kinetic energy is absorbed by the liquid, resulting in increased temperature. Examples: Steam releases much energy when it condenses to a liquid and moistens the skin—hence, it produces a more damaging burn than from same-temperature 100  C boiling water. You feel warmer in a moist shower stall because the rate of condensation exceeds the rate of evaporation.

© 2010 Pearson Education, Inc. Condensation in the atmosphere When the temperature of the atmosphere is low, the water molecules in the air move slowly. Slow-moving water molecules stick together, causing condensation. Example: Fog and clouds created when air rises Condensation

© 2010 Pearson Education, Inc. Boiling Boiling process Rapid evaporation from beneath the surface of a liquid.

© 2010 Pearson Education, Inc. Boiling Boiling point depends on pressure. Example: Buildup of vapor pressure inside a pressure cooker prevents boiling, thus resulting in a higher temperature that cooks the food. Boiling point is lower with lower atmospheric pressure. Example: Water boils at 95  C in Denver, CO (high altitude) instead of at 100  C (sea level).

© 2010 Pearson Education, Inc. Exit Ticket Pg 312 # 1, 11, 23, 24, 30, 42, 44, 52

© 2010 Pearson Education, Inc. Ch 18

© 2010 Pearson Education, Inc. The First Law of Thermodynamics States that the heat added to a system transforms to an equal amount of some other form of energy. Heat added to system = increase in internal energy + work done by system The first law of thermodynamics is a restatement of the law of conservation of energy: Energy can neither be created nor destroyed.

© 2010 Pearson Education, Inc. Adiabatic Processes Example: When we compress air using a bicycle pump, i.e., when we do work on the system, we heat the air up, i.e., increase its internal energy. Heat added to system = 0 So: Increase/Decrease in internal energy = work done on/by system

© 2010 Pearson Education, Inc. Second Law of Thermodynamics- The entropy (disorder) of the universe increases in all natural processes Heat itself never spontaneously flows from a cold object to a hot substance. Example: –In summer, heat flows from the hot air outside into the cooler interior. –In winter, heat flows from the warm inside to the cold exterior. Heat can flow from cold to hot only when work is done on the system or by adding energy from another source. –Example: heat pumps, air conditioners

© 2010 Pearson Education, Inc. Second Law of Thermodynamics Every heat engine has –a reservoir of heat at a high temperature. –a sink at lower temperature. Every heat engine 1.gathers heat from the reservoir at high temperature. 2.converts some of this heat into mechanical work. 3.expels the rest of the heat to the sink at lower temperature.

© 2010 Pearson Education, Inc. Exit Ticket Pg 329 # 4, 6, 7, 9, 11, 33, 35, 40