Thermodynamics Teacher Guide
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Thermodynamics Teacher Guide Hands-on lab experiments to explore the principles and transfer of thermal energy. Pri Ele Int Grade Level: Sec Secondary Subject Areas: Science Language Arts Math NEED Mission Statement Teacher Advisory Board Shelly Baumann Rockford, MI Barbara Lazar Albuquerque, NM Constance Beatty Kankakee, IL Robert Lazar Albuquerque, NM Amy Constant Raleigh, NC Leslie Lively Porters Falls, WV Nina Corley Galveston, TX Jennifer Winterbottom Pottstown, PA Regina Donour Whitesburg, KY Mollie Mukhamedov Port St. Lucie, FL Linda Fonner New Martinsville, WV Don Pruett Jr. Sumner, WA Samantha Forbes Vienna, VA Josh Rubin Palo Alto, CA Robert Griegoliet Naperville, IL Joanne Spaziano Cranston, RI Michelle Garlick Gina Spencer Virginia Beach, VA Viola Henry Thaxton, VA Tom Spencer Chesapeake, VA Bob Hodash Jennifer Trochez MacLean Los Angeles, CA DaNel Hogan Tucson, AZ Greg Holman Paradise, CA Linda Hutton Kitty Hawk, NC Matthew Inman Spokane, WA The mission of The NEED Project is to promote an energy conscious and educated society by creating effective networks of students, educators, business, government and community leaders to design and deliver objective, multisided energy education programs. Teacher Advisory Board Statement In support of NEED, the national Teacher Advisory Board (TAB) is dedicated to developing and promoting standardsbased energy curriculum and training. Permission to Copy NEED materials may be reproduced for non-commercial educational purposes. Energy Data Used in NEED Materials NEED believes in providing the most recently reported energy data available to our teachers and students. Most statistics and data are derived from the U.S. Energy Information Administration’s Annual Energy Review that is published yearly. Working in partnership with EIA, NEED includes easy to understand data in our curriculum materials. To do further research, visit the EIA web site at www.eia.gov. EIA’s Energy Kids site has great lessons and activities for students at www. eia.gov/kids. Joanne Trombley West Chester, PA Jen Varrella Fort Collins, CO Carolyn Wuest Pensacola, FL Wayne Yonkelowitz Fayetteville, WV 1.800.875.5029 www.NEED.org © 2014 Printed on Recycled Paper 2 Thermodynamics Teacher Guide Thermodynamics Teacher Guide Table of Contents © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 Standards Correlation Information 4 Teacher Guide 5 Equipment Needed 7 Equipment Sources 9 Teacher Demonstrations 11 Exploration: Calibrating a Thermometer 13 Student Lab Answer Key 14 Unit Exam 17 Unit Exam Answer Key 21 Evaluation Form 23 1.800.875.5029 www.NEED.org 3 Standards Correlation Information www.NEED.org/curriculumcorrelations Next Generation Science Standards This guide effectively supports many Next Generation Science Standards. This material can satisfy performance expectations, science and engineering practices, disciplinary core ideas, and cross cutting concepts within your required curriculum. For more details on these correlations, please visit NEED’s curriculum correlations web site. Common Core State Standards This guide has been correlated to the Common Core State Standards in both language arts and mathematics. These correlations are broken down by grade level and guide title, and can be downloaded as a spreadsheet from the NEED curriculum correlations web site. Individual State Science Standards This guide has been correlated to each state’s individual science standards. These correlations are broken down by grade level and guide title, and can be downloaded as a spreadsheet from the NEED web site. 4 Thermodynamics Teacher Guide Teacher Guide A unit that introduces students to the basic concepts of thermodynamics—atomic structure, atomic and molecular motion, states of matter, heat transfer, thermal expansion, specific heat, and heats of fusion and vaporization. &Background Time Thermodynamics is a hands-on laboratory unit that explores thermal energy. These activities encourage the development of cooperative learning, math, science, and critical thinking skills. Eight to ten 45-60 minute class periods, plus homework Lab Two in this unit contains activities designed to familiarize your students with conduction, and varying levels of conductivity. The first activity uses containers made from three different materials— steel, porcelain, and foam. While each uses the same volume of water, 30 mL, the variability in size and shape of container might lead to some minor discrepancies in the results vs. the expected results of the activity. Variations such as the surface area of the water, container thickness, etc., may cause students’ results to be inaccurate in terms of conductivity of the materials. They should find the conductivities to range from steel being most conductive then porcelain and finally foam being least conductive. We suggest that you conduct the activity once yourself, and experiment with different containers you have on-hand, until you get the desired result. Grade Level This unit is designed for high school students. 2Preparation Familiarize yourself with the Teacher Guide and Student Guide. Decide if you wish to conduct the Exploration exercise and the Teacher Demonstrations. Obtain the equipment needed for the Exploration, Teacher Demonstrations, and student labs (see Equipment Needed on pages 7-8). Read and familiarize yourself with instructions for various materials (i.e. specific heat slide, steam generator, etc.). Distilled water and tap water have differences in their specific heats and heats of fusion and vaporization. When using tap water, these differences could account for some distortion in student results. If distilled water is available, it is suggested for use where water is needed, but is not necessary. When providing heat for activities, using a Bunsen burner will be effective. If Bunsen burners are not available, alcohol burners or Sterno cans will serve as a suitable substitute. Divide your students into six groups. Make one copy of the Unit Exam for each student or group, as you choose (see pages 17-20). Set up the equipment at six laboratory stations (see the Student Guide) and do the following things before students are ready to work: Lab 1 Fill two test tubes with screw caps about one-third full of corn syrup and seal. Lab 2 Prepare wax birthday candle pieces. Cut birthday candles into pieces, approximately 5-7 mm in length. Each group will need five pieces, but make extras to allow for any mistakes or errors. The pieces should all be the same size—large enough to not all melt completely, but small enough to “stick” to the conductometer. © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 5 Lab 4 Fill two 50 mL graduated cylinders—one with 40 mL of glycerin at room temperature and one with 40 mL of water at room temperature— and seal. Fill two 250 mL graduated cylinders with 200 mL of isopropyl alcohol and seal with stoppers. Place a small balloon over the end of the expansion tube. Lab 6 Make ice cubes, using distilled water, if possible. Place the steam generator for Lab 6 where you can directly supervise its use. Procedure Day 1: Introduction Introduce the unit to the class, explaining that the students will work in small groups to investigate the concepts of thermal energy, conducting different experiments each day for the next six days. You may want to discuss rules for working in groups. Explain that each group should assign tasks to members of the group—recording data, timing, etc. Encourage the students to assign group members to different tasks each day. For younger students who are not familiar with the basic concepts and terminology, allot an extra class period to introduce the unit. Place students into groups, assign one lab station to each group, and distribute the Student Guides. Go over the Student Guide with the class, giving instructions for using the guides. Review Scientific Concepts on page 3 of the Student Guide. Review Metric Measurements and Conversions on page 4 of the Student Guide. Review Lab Safety Rules on page 5 of the Student Guide, as well as any additional safety rules that you require. Review the “Learn About It” sections of the Student Guide for all six stations, using the Teacher Demonstrations (pages 11-12 of the Teacher Guide) for each lab, if desired. Have students complete the recording and calculating sections of Lab One for that demonstration. (The labs are written as separate units and are not dependent on the previous labs. The concepts, however, do build on each other.) Optional: Have students conduct the Exploration exercise (page 13 of the Teacher Guide), calibrating thermometers in their lab groups as an additional one-day introduction to the unit. Evaluate the exercise with the class. Instruct student groups to preview the lab stations to which they have been assigned. Instruct the students to complete the “Think About It” questions for their labs as homework. (Student Lab Answer Key is on page 14 of the Teacher Guide.) Days 2–7: Student Labs Rotate the groups through the lab stations. Remind the students at the beginning of each day about the lab safety rules. Note: It is recommended that the teacher operate the steam generator (Lab 6) and directly supervise its use by students. Assign the “Think About It” questions for the next day’s lab for homework. Day 8: Evaluation As a class, discuss the labs, results, and questions and problems included in the Student Guide. Note: The questions in the “Make Sure You Understand It” sections are designed to be progressively difficult. For younger students, you may wish to assign only the first one or two questions. Have the students take the Unit Exam in groups or individually. 6 Thermodynamics Teacher Guide Equipment Needed ACTIVITY SPECIALIZED LAB EQUIPMENT Demo 1 COMMON LAB EQUIPMENT LAB CHEMICALS AND OTHER CONSUMABLES 2 250 mL Graduated cylinders Beads Triple beam balance or electronic Marbles balance Demo 2 Heat transfer set Water—hot and cold Demo 3 Gas convection apparatus Touch paper or incense Candle Demo 4 Ball and ring set Bunsen burner Demo 5 Specific heat slide Water 600 mL Beaker Bunsen burner Ring stand or tripod Tongs Triple beam balance or electric balance Demo 6 Palm Glass Exploration 6 Uncalibrated thermometers 6 100 mL Beakers 6 Bunsen burners 6 Permanent markers waterproof ) 6 Ring stands or tripods 6 Rulers Beaker tongs Ice Water (fine-tip, Lab 1 2 Test tubes with screw caps 100 mL Graduated cylinder 2 250 mL Graduated cylinders 25 mL Graduated cylinder Triple beam balance or electronic balance Eye droppers 12-13 g Sodium chloride per group 140 mL Ethyl alcohol per group Corn syrup Ice Water Waxed paper Lab 2 Conductometer Steel crucible with lid Beaker Large safety pin Porcelain crucible with lid Ring stand with clamp Shallow pan Thermometers Watch with second hand Beaker tongs Candle (or alcohol lamp) Ice Matches Birthday candles Foam cup with lid Water Safety pin Lab 3 Infrared lamp Radiation cans Thermoconductivity strip U-tube Ring stand with clamp Thermometers Watch with second hand Candle (or alcohol lamp) Food coloring Index card Matches Ruler Water Tape © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 7 Lab 4 Compound bi-metal bar Gas expansion tube 2 50 mL Graduated cylinders 2 Stoppers to fit 50 mL g.c. 2 Stoppers to fit 250 mL g.c. 4 1,000 mL Beakers 4 250 mL Graduated cylinders 4 Thermometers Beaker tongs 40 mL Glycerin 400 mL Isopropyl alcohol Candle (or alcohol lamp) Water Ice Small balloon Matches Lab 5 Specific heat specimen set 100 mL Graduated cylinder 5 Thermometers 600 mL Beaker Bunsen burner Ring stand or tripod Safety gloves Tongs Triple beam or electronic balance 5 Foam cups with lids Water Marker Lab 6 Steam generator with hose 2 250 mL Graduated cylinders 2 Thermometers Bunsen burner Ice cube tray Ring stand Beaker tongs 2 Large foam cups with lids Water Ice cubes made from distilled water NOTE: Hot plates can also be substituted for Bunsen burners in stations 5 and 6. 8 Thermodynamics Teacher Guide Equipment Sources Company Catalog Number Description The following items are specific to the activities in this unit and may not be already present in your lab inventory: Nasco SB33231M 60 mL Test tubes with screw caps – pkg 15 Nasco SB07985M Ball and ring set Nasco S00188M Compound (bi-metal) bar Nasco S00187M Conductometer Sargent Welch Nasco WLC95265-057 S00185M Ethyl alcohol (Reagent, anhydrous, denatured) Gas convection apparatus Sargent Welch CP77300-00 Sargent Welch WLC94573-07 Sargent Welch WL6819R Heat transfer set Nasco C09857M Infrared lamp with reflector Nasco KM00639M Isopropyl alcohol, reagent ACS Nasco SA09087M Palm glass (pulse glass) Nasco SB26244M Radiation cans Nasco C11387N Glass thermometer tube Glycerin (Lab grade, 1 L bottle) Clamp reflector bowl lamp Sargent Welch WLS1808-75 Specific heat slide Sargent Welch WLS1800-33 Steam generator with hose Sargent Welch WLS-23835-C Steel crucible with lid, 50 mL capacity 20020 Thermoconductivity strip (fickle foam) Nature’s Workshop Sargent Welch WL1728 Sargent Welch WLS80290-10 Nasco Touch paper SB4699M Ungraduated thermometers U-tube (liquid convection apparatus) The following items are commonly found in most school science lab inventories, but we have listed sources and catalog numbers for your convenience: Sargent Welch WLS4675-H 100 mL Beakers (pkg of 12) Sargent Welch WLS4675-M 600 mL Beakers Sargent Welch WLS4675-P 1000 mL Beakers Sargent Welch WLS24638-17C 25 mL Graduated cylinders Sargent Welch WLS24638-17D 50 mL Graduated cylinders Sargent Welch WLS24638-17E 100 mL Graduated cylinders Sargent Welch WLS24638-17G 250 mL Graduated cylinders Sargent Welch WLS12710 Sargent Welch WLS1761-51 Bunsen burner (natural gas) Sargent Welch WLS73045-B Clamp for ring stand Sargent Welch WLS41002 Sargent Welch WLS23687-J Porcelain crucible with lid, 50 mL capacity Sargent Welch WLS78305-B Ring stand © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 Alcohol burner Hot plate 1.800.875.5029 www.NEED.org 9 Sargent Welch WLS-82270 Sargent Welch WLS73326-30 Sargent Welch WL5681 Sargent Welch WLS80036 Thermometers (student) Sargent Welch WLS1766-09 Timers (Ward’s, pack of 6) Sargent Welch WLS1761-69 Triple beam balance (Ohaus) Sargent Welch WLS82505-A Tripod Nasco KI01066(A)M Dropper, plastic, eye (package of 15) Nasco SA04392M Safety tongs Stoppers (2 lb. package assortment, sizes 00-8) Thermometers (package of 15, dual scale) Beaker tongs Web sites for suppliers: Sargent Welch www.sargentwelch.com Nasco www.eNasco.com Frey www.freyscientific.com Nature’s Workshop workshopplus.com The following items are easily obtained locally. Therefore, we are not providing sources or catalog numbers for them. However, if you have difficulty obtaining these items, please contact us and we will help you locate them. Beads (small) Food coloring Large safety pin Small balloon Birthday candles Marbles Candles Granulated sugar (7-10 g per lab group) Markers (permanent, fine tip) Sterno cans (substitute for Bunsen burner) Corn syrup Ice cube tray Matches Tape Distilled water Incense Ruler Waxed paper Foam cups with lids Index card Shallow pan 10 Thermodynamics Teacher Guide Teacher Demonstrations Lab One Demo | MARBLES AND BEADS REPRESENT ATOMS AND MOLECULES. Materials 2 250 mL Graduated cylinders Marbles Beads Triple beam balance Procedure 1. Record the mass of one empty cylinder. Fill the cylinder with 100 mL of marbles and record the mass. 2. Record the mass of the second cylinder. Fill the cylinder with 100 mL of beads and record the mass. 3. Carefully pour the beads into the cylinder of marbles. Gently tap the cylinder several times to settle the beads into the cylinder. Record the volume and mass of the cylinder. Lab Two Demo | HEAT TRANSFERS FROM ONE CUP TO ANOTHER THROUGH ALUMINUM ROD. Materials Heat transfer set Hot (~50ºC) and cold water (~5-10ºC) Procedure 1. Fill one cup in the set with hot water and the other with an equal volume of cold water. Note temperatures. 2. Observe as the aluminum rod conducts thermal energy from the hot water to the cold water and the temperatures equalize. For further explorations, use different materials as the conductor. Lab Three Demo | GAS CONVECTION APPARATUS DEMONSTRATES HOW WARM AIR RISES. Materials Gas convection apparatus Touch (smoke) paper or incense Candle Procedure 1. Light a candle under one chimney of the apparatus. Light touch paper or incense and hold the smoking end over other chimney. 2. Observe as the smoke from the smoke source is drawn down the chimney to replace the rising air in the other chimney. 3. If the smoke is difficult to see, place a piece of paper (white will usually work) to enhance viewing of smoke. © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 11 Lab Four Demo | BALL AND RING DEMONSTRATES EXPANSION OF METAL AS HEAT IS ADDED. Materials Ball and ring Bunsen burner or alcohol lamp Procedure 1. Demonstrate how the ball fits easily through the ring at room temperature. 2. Heat the ball only to demonstrate how the metals have expanded and the ball will not fit through the ring. Lab Five Demo | DEMONSTRATE THE DIFFERENT SPECIFIC HEAT OF SEVERAL METALS. Materials Specific heat slide Water Bunsen burner, alcohol lamp, or hot plate Tripod or ring stand Tongs 600 mL Beaker Triple beam balance Procedure 1. Weigh the metal samples to show that they all have the same mass, then heat them in a beaker of boiling water for several minutes. 2. Place the samples in the wax of the specific heat slide to demonstrate how equal masses of different metals contain different amounts of heat when they are at the same temperature. Lab Six Demo | PALM GLASS DEMONSTRATES CHANGE OF STATE WITH THE ADDITION OF THERMAL ENERGY. Materials Palm glass Procedure 1. Hold the liquid-filled bulb of the palm glass in your hand. The thermal energy from your hand changes the liquid in the bulb into a gas, as indicated by the bubbling of the liquid in the other bulb. The liquid in the bulb is ethyl alcohol, a liquid with a boiling point near the temperature of your body temperature. 12 Thermodynamics Teacher Guide Exploration: Calibrating a Thermometer Objective Students will use critical thinking skills to calibrate a thermometer without instructions. 2Preparation Place students in six groups. Make the following equipment and materials accessible to the students, but do not instruct them about which equipment or materials to use. For example, you could tell the students they can use any equipment and materials on a given shelf. Materials 6 Uncalibrated thermometers 6 100 mL Beakers 6 Permanent, fine-tip, waterproof markers 6 Ring stands or tripods 6 Bunsen burners or alcohol lamps Water Ice 6 Rulers Procedure 1. Give each group of students an uncalibrated thermometer and a marker. 2. Instruct the students to review the Lab Safety Rules on page 5 of their Student Guides. 3. Instruct the students to brainstorm within their groups to devise a method to calibrate their thermometers from -10ºC to 120ºC. Depending on the level of your students, you can require them to calibrate the thermometers to both Celsius and Fahrenheit scales. 4. Instruct each group to write down a list of the materials they will need to accomplish the task and give it to you. If the list of materials is safe and reasonable in your judgment, allow the group to proceed, even if the materials may not accomplish the task. 5. If a group has difficulty devising a list, ask questions to guide them in the right direction, but do not tell them how to proceed. 6. If a group discovers they need additional materials as they proceed, instruct them to obtain your approval before obtaining the materials. 7. After 15-30 minutes, evaluate the activity with the students, checking their calibrations by placing the thermometers in boiling water (100ºC/212ºF at sea level) and at the top of a beaker of ice water (0ºC/32ºF). The calibrations between the markers should be uniform. You can also use body temperature (37ºC/98.6ºF) to validate the calibrations. © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 13 Student Lab Answer Key Lab 1 | THINK ABOUT IT 1. Mass will remain the same, volume will increase. 2. Hot water will have more space between the molecules. A given volume of hot water should weigh less than the same volume of cold water. Look for students to design a procedure that provides an answer to their hypothesis. Lab 1 | MAKE SURE YOU UNDERSTAND IT 1. 200 mL + [200 - (200 x 0.05)] mL = 200 + 190 = 390 mL Lab 2 | THINK ABOUT IT 1. The bar’s temperature should be cooler than the temperature of the hot water, but warmer than that of the cool water. 2. Diamond 3. Foam (Polystyrene) 4. Concrete is a better conductor than wood. 5. Copper - best conducting material from which a pan can be made. 6. As insulators - to keep things hot or cold, protect us from burns, etc. Lab 2 | MAKE SURE YOU UNDERSTAND IT 1. Aluminum is more than twice as conductive as brass. 2. Nickel is 11 times as conductive as glass - 11,000 joules per second. 3. Nickel - 8 minutes 15 seconds; Steel - 4 minutes 45 seconds; Brass - 35.5 seconds; Copper - 10 seconds; and Aluminum - 16.25 seconds. Lab 3 | THINK ABOUT IT 1. Radiant energy is striking your skin. The radiant energy is absorbed by the molecules in your skin, and their thermal energy is increased. 2. Heat the first floor - the warmer air would rise to the second floor. 3. Convection currents carry the molecules of smoke all over the house. 4. In hot sun, it is cooler with long sleeves on. They limit the amount of thermal energy converted from radiant energy. Light colors reflect more radiant energy. 5. The land heats up faster than the ocean. As the air over the land heats up, it rises, and the cooler air over the ocean rushes in to take its place. Lab 3 | MAKE SURE YOU UNDERSTAND IT 1. Energy from the sun is absorbed by the concrete, the water in the sunny end of the pool, and the air above the pool. The concrete warms the shady end of the pool via conduction. Convection currents in the pool warm the water in the pool, and radiation from the water and concrete warm the air creating another convection current. The warmest water in the pool is at the top, because warm water is less dense and rises above cooler, more dense water. 14 Thermodynamics Teacher Guide Lab 4 | THINK ABOUT IT 1. Air and gases expand the most. Pyrex glass expands the least. 2. Steel and concrete have the same cubic expansion rate. If a different metal is used, it might crack the concrete as it expands or contracts. 3. Pyrex expands very little when heated, much less than regular glass. 4. The materials used in building the bridge should be given enough room to expand and contract. Otherwise, the bridge might buckle in the summer, or have large cracks form in the winter. 5. Ethyl alcohol would register the slightest changes because it expands the most. Lab 4 | MAKE SURE YOU UNDERSTAND IT Question 1 Volume change = (10m3)(500ºC)(0.000069/ºC) Volume change = 0.345m3 New volume = 10.345m3 Question 2 10mL = (500mL)(100ºC)(cubic expansion rate) 10mL/50,000mLºC = cubic expansion rate = 0.0002/ºC Question 3 1.1L = (100L)•(temperature change)•(0.00112/ºC) 1.1L = (0.112L/ºC)•(T) 1.1L/0.112L/ºC = T = 9.8ºC Lab 5 | THINK ABOUT IT 1. Generally, as the density of a substance increases, the specific heat decreases. 2. Generally, as the atomic mass of a substance increases, its specific heat decreases. As atomic mass increases, so does density. 3. Water 4. Gold and Lead 5. The human body is mostly water. The temperature of a body could tell a detective how long ago the murder had occurred. Lab 5 | MAKE SURE YOU UNDERSTAND IT Question 1 Heat lost = Heat gained (10g)(150ºC - T)(0.385J/gºC) = (50g)(T - 30ºC)(4.184J/gºC) T = final temperature of copper and water (3.85g J/g ºC)(150ºC - T) = (209.2g J/g ºC)(T -3 0ºC) 577.5J - 3.85T = 209.2T - 6276J 6853.5 = 213.05T T = 32.17ºC © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 15 Question 2 Temperature change for metal = (125ºC - 22.75ºC) = 102.25ºC Temperature change for water = (22.75ºC - 20ºC) = 2.75ºC Heat lost by the metal = Heat gained by the water (Specific Heat)(102.25ºC)(10g) = (4.184J/gºC)(40g)(2.75ºC) (Specific Heat)(1022.5ºC • g ) = 460.24J Specific Heat = 460.24J/1022.5g • ºC Specific Heat = 0.450J/g • º C = iron Question 3 Eventually all would reach the same temperature. Lead has the lowest specific heat, then iron, then aluminum. Aluminum would absorb the most thermal energy when heated. Lead would lose the least thermal energy when cooled. Lab 6 | THINK ABOUT IT 1. There is no direct correlation. 2. It takes more energy to change a liquid into a gas because almost all the force of attraction between the atoms or molecules is being overcome. Particles are being moved further apart, which requires significant amounts of energy. 3. Copper requires the most amount of heat energy to change from a liquid into a gas. 4. Mercury requires the least amount of heat energy to change from a solid into a liquid. 5. There is no direct correlation. Lab 6 | MAKE SURE YOU UNDERSTAND IT Question 1 (20g)(80cal/g) + (20g)(T - 0ºC)(1.0cal/g ºC) = (50g)(100ºC - T)(1.0cal/g ºC) T = Final temperature of water (1,600g cal/g) + (20g T cal/g ºC) = (5,000 ºC cal g/g ºC) - (50g cal T/g ºC) 1,600cal + 20cal T = 5,000cal - 50cal T 70cal T = 3400cal T = 3,400cal/70cal = 48.57ºC Question 2 (2g)(540cal/g) + (2g)(100ºC - T)(1.0cal/g ºC) = (50g)(T - 20ºC)(1.0cal/g ºC) 1,080cal + (2g cal/g ºC)(100ºC - T) = (50g cal/g ºC)(T-20ºC) 1,080cal + 200cal - 2cal T = 50cal T - 1,000cal 2,280cal = 52cal T 2,280cal/52cal = T = 43.85ºC Question 3 Steam temperature change = 100ºC - 82ºC = 18ºC Water temperature change = 82ºC - 20ºC = 60ºC (Xg)(540cal/g) + (Xg)(18ºC)(1.0cal/g ºC) = (90g)(62ºC)(1.0cal/g ºC) 540X cal + 18X cal = 5,580cal 558X cal = 5,580cal X = 5,580cal/558cal = 10g Question 4 (100g)(80cal/g) + (100g)(T - 0ºC)(1.0cal/g ºC) = (20g)(540cal/g) + (20g)(100ºC - T)(1.0cal/g ºC) 8,000cal + 100cal T = 10,800cal + 2,000cal - 20cal T 120cal T= 4,800cal T = 40º C 16 Thermodynamics Teacher Guide Unit Exam Part I | CIRCLE THE LETTER THAT CORRECTLY ANSWERS EACH QUESTION. QUESTIONS 1-20 ARE WORTH 1 POINT EACH. 1. The word thermodynamics means __________. a. production of heat b. movement of heat c. both a and b d. neither a nor b 2. Why do atoms or molecules in solids remain in a fixed position? a. They are held in place by the magnetic field of the Earth. b. They have too much energy to move freely. c. They do not have enough energy to overcome the attractive forces between them. d. They do not have enough energy to overcome the gravitational attraction between them. 3. Approximately how many elements comprise everything in the universe? a. 10 b. 100 c. 1,000 d. The number is infinite 4. As the vibration of the molecules in a substance increases, the temperature of the substance ________. a. increases b. remains the same c. decreases 5. In which state of matter do the particles have the least thermal energy? a. Gas b. Liquid c. Solid d. They’re all the same 6. In which state of matter do the particles have the most thermal energy? a. Gas b. Liquid c. Solid d. They’re all the same 7. Increasing the thermal energy of a substance causes the greatest increase in volume in which state of matter? a. Gas b. Liquid c. Solid d. They’re all the same 8. What happens to molecules in a liquid when the liquid is heated? a. They are able to move around the container more easily, and overcome their attractive forces more easily. b. They move faster and move further apart. c. They move slower and move closer together. d. Both a and b. 9. Three containers – 1.0 L, 5.0 L, and 10.0 L – are filled with sand and placed in a room at 22ºC. After 24 hours, which container of sand has molecules vibrating at the greatest rate? a. 1.0 L b. 5.0 L c. 10.0 L d. They’re all the same 10. Which of the three containers mentioned in question #9 contains the most total thermal energy? a. 1.0 L b. 5.0 L c. 10.0 L d. They’re all the same 11. Specific heat of a substance measures ________. a. the amount of energy required to raise the temperature of a substance one degree b. the amount of energy required to raise the temperature of one gram of a substance one degree c. the amount of time required to reach the boiling point d. total thermal energy in a substance 12. Generally speaking, as density increases, the specific heat of a substance ________. a. decreases b. stays the same c. increases d. is not related to density 13. Substances in which state of matter cannot transfer thermal energy by convection? a. Gasb. Liquid c. Solid d. They all are able to transfer thermal energy via convection. © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 17 14. Half of your bare foot, at 37ºC, is on a tile floor, and the other half is on a rug. If the temperature of the room is 24ºC, which statement below is true? a. The rug is a better conductor than the tile. b. The rug is warmer than the tile. c. The temperature of the rug and tile are the same. d. Thermal energy is being transferred from your foot to the tile, but not the rug. 15. To heat a room efficiently, the heating elements or vents should be placed _________. a. on the floor b. in the middle of the wall c. on the ceiling d. wherever they fit best; it doesn’t matter where they are placed 16. The diagram on the right shows two metal bars in contact with each other. The temperature of bar A is initially 40ºC and the temperature of bar B is initially 10ºC. Which statement below best describes the thermodynamics of the system? a. Bar A will transfer thermal energy to bar B via conduction. b. Bar A will transfer thermal energy to bar B via radiation. c. Bar B will transfer thermal energy to bar A via conduction. d. Bar B will transfer thermal energy to bar A via convection. A=40ºC B=10ºC 17. If two different metal samples, each with masses of 50 grams at 100 C, are placed into beakers with 200 mL of water at 10ºC, which metal will cause the greater increase in the water’s temperature? The metal with the _________. a. higher conductivity º b. higher heat of fusion c. higher melting point d. higher specific heat 18. When a substance changes from a liquid into a gas at a constant temperature _________. a. energy is absorbed b. energy levels remain the same c. energy is released 19. Which of the following contains the greater amount of thermal energy? a. One gram of steam at 100ºC. b. One gram of water at 100ºC. c. Both water and steam at 100ºC contain the same amount of thermal energy. 20. Thermal energy is added to a substance, yet its temperature remains the same. This is because _________. a. temperature and thermal energy are not related b. the substance is a good conductor of thermal energy c. the substance is a good insulator of thermal energy d. the substance uses the thermal energy to change states of matter 18 Thermodynamics Teacher Guide Thermodynamics Table Specific Heat (cal/gºC) Cubic Expansion (m3/ºC) Conductivity [cal/(sec x m x ºC)] Melting Point (ºC) Heat of Fusion (cal/g) Boiling Point (ºC) Heat of Vaporization (cal/g) Lead 0.030 87 x 10-6 147 327 5.5 1,750 205 Copper 0.092 -6 51 x 10 1,633 1,083 49.5 2,566 1,130 Aluminum 0.215 69 x 10-6 1,005 660 76.8 2,519 3,905 Water 1.000 207 x 10 3 0 80.0 100 540 Substance -6 Part II | TO ANSWER QUESTIONS 21-28, REFER TO THE TABLE ABOVE. Questions 21-24 are worth 2 points each. Questions 25-28 are worth 8 points each. 21. Which solid will expand the most when thermal energy is added? 22. Which substance is the best conductor of thermal energy? 23. Which metal will turn into a liquid first when put into an industrial oven? 24. Which substance would require the most thermal energy to increase the temperature of a one gram sample 1ºC? 25. How much thermal energy must be added to a 10 gram sample of aluminum to increase its temperature from 100ºC to 120ºC? 26. A block of aluminum with a volume of 100m3 at 0ºC is heated to 200ºC. What is the block’s new volume? 27. A 50 gram piece of ice at 0ºC is placed in 100 grams of water at 100ºC. When the ice has completely melted, what is the resulting temperature of the water? 28. A 10 gram sample of copper at 983ºC is heated until it turns into a liquid at 1083ºC. How much thermal energy is required? © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 19 Part III | ANSWER TWO OF THE FOLLOWING QUESTIONS. EACH QUESTION IS WORTH 10 POINTS. 29. A drinking glass is taken out of the freezer and placed on a table on a warm, humid day. Explain what happens to the glass in the first 30 seconds, in 30 minutes, and in 24 hours. 30. On a very cold day —and on a dare—a student who doesn’t understand thermodynamics touches his/her tongue to a metal pole. The temperature of the metal is –10ºC. Explain in thermodynamic terms what happens and why. 31. You want to store the thermal energy collected by your passive solar home during the day. You want to build planters in the room with large, south facing windows to store the energy. What material should you use to build the planters—wood, concrete, or metal—and why? What else should you do to prevent thermal energy loss from conduction? 32. Thermos bottles can keep liquids cold or warm, because they have a partial vacuum between the inner container holding the liquid and the highly reflective outer surface. Explain why this construction design is so effective. 20 Thermodynamics Teacher Guide Unit Exam Answer Key 1. b 21. lead 2. c 22. copper 3. b 23. lead 4. a 24. water 5. c 25. (10g)(20ºC)(0.215 cal/gºC) = 43.0 cal 6. a 26. Expansion = (Original Volume)(Temperature Change) • (Expansion Rate) 7. a 8. d 9. d 10. c 11. b Expansion = (100m3)(200ºC) • 69 x 10-6 Expansion = (1.38 x 10-1m3) = 1.38m3 New Volume = 101.38m3 27. Heat lost = Heat gained 12. a (50g)(334.72J/g) + (50g)(T - 0ºC)(4.184J/g • ºC) = (100g)(100ºC - T)(4.184J/g ºC) 13. c 16,736J + 209.2 T J/ ºC = 41,840J - 418.4 T J/ ºC 14. c 627.6T J/ ºC = 25,104 J 15. a 16. a 17. d 18. a T = 40 = Final temperature 40ºC 28. Heat required = (10g)(100ºC)(0.092cal/g/ºC) + (10g)(49.5cal/g) Heat required = 92 cal + 495 cal = 587 cal 19. a 20. d 29. Water molecules are always in the air, especially on humid days. When these water molecules strike the ice-cold glass (coming directly from the freezer, the glass is less than 0ºC), they give off a lot of their energy to the less energetic molecules of the glass. The energy loss is so great for the gas molecules that they turn directly into ice, and in 30 seconds you get a frosted glass. The glass continues to absorb energy from the warm room and its temperature begins to rise. Now the heat from the glass provides enough energy to the molecules of ice to break the forces of attraction that kept the molecules in the solid state. The ice will change into water. In addition to the melted ice water on the glass, water molecules in the air continue to strike the glass, changing into water now instead of ice. In 30 minutes, the glass reaches room temperature, and is covered with drops of water. In a day, all the water molecules gain enough energy to leave the forces of attraction of the glass and other water molecules and fly off into the air. The water evaporates and changes back into gas molecules. 30. The atoms and molecules in the –10ºC metal pole possess little internal energy. The saliva on the child’s tongue is mostly water. When these body temperature (37ºC) water molecules come in contact with the –10ºC metal pole they transfer a great deal of their energy to the less energetic atoms in the pole. The water molecules on the child’s tongue and on the pole lose so much energy that they freeze into ice, trapping the child until the ice melts, one way or another. 31. A planter that could store a lot of thermal energy during the day, so that it could release more energy during the night, would be the best choice. Concrete has the highest specific heat of the three potential products. This means concrete will take longer to heat up, but will also provide more thermal energy to the room when the sun is gone. A well insulated home will prevent this valuable solar thermal heat from leaving the building. The trapped air in the insulation does not conduct heat well, therefore keeping the heat in the building longer. 32. The partial vacuum between the inner and outer shells of the container prevents heat transfer by conduction and convection for most areas of the bottle. The reflective surface of the outer shell reduces the amount of radiant energy absorbed by the shell. Together, these two factors slow heat from entering or escaping from the bottle. © 2014 The NEED Project P.O. Box 10101, Manassas, VA 20108 1.800.875.5029 www.NEED.org 21 Youth Awards for Energy Achievement All NEED schools have outstanding classroom-based programs in which students learn about energy. Does your school have student leaders who extend these activities into their communities? To recognize outstanding achievement and reward student leadership, The NEED Project conducts the National Youth Awards Program for Energy Achievement. This program combines academic competition with recognition to acknowledge everyone involved in NEED during the year—and to recognize those who achieve excellence in energy education in their schools and communities. What’s involved? Students and teachers set goals and objectives, and keep a record of their activities. If students like, they can combine their planning materials and activities into a binder or portfolio that highlights their goals, outreach opportunities, and their evaluation of the activities. Students will then use this binder or portfolio to help them create a digital project to submit for judging. In April, digital projects should be uploaded to the online submission site. Want more info? Check out www.NEED.org/Youth-Awards for more application and program information, previous winners, and photos of past events. 22 Thermodynamics Teacher Guide Thermodynamics Evaluation Form State: ___________ Grade Level: ___________ Number of Students: __________ 1. Did you conduct the entire unit? Yes No 2. Were the instructions clear and easy to follow? Yes No 3. Did the activities meet your academic objectives? Yes No 4. Were the activities age appropriate? Yes No 5. Were the allotted times sufficient to conduct the activities? Yes No 6. Were the activities easy to use? Yes No 7. Was the preparation required acceptable for the activities? Yes No 8. Were the students interested and motivated? Yes No 9. Was the energy knowledge content age appropriate? Yes No 10.Would you teach this unit again? Yes No Please explain any “no” statements below How would you rate the unit overall? excellent good fair poor How would your students rate the unit overall? excellent good fair poor What would make the unit more useful to you? Other Comments: Please fax or mail to: The NEED Project P.O. Box 10101 Manassas, VA 20108 FAX: 1-800-847-1820 © 2014 The NEED Project P.O. 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