Melting Ice Cubes aka Thermodynamics and Heat Tra……

1、1Melting Ice Cubesaka. Thermodynamics and Heat TransferHIGH ASPIRATIONSCreated by:Dave JohnsonKathy Holliday-Darr2Miracle ThawuIs it really a miracle?uLets check it out3Melting Ice Cubes: “Icebreaker” JuEstablish teams and have them create a company nameu Run first experimentFirst experiment objecti

2、ve: Determine how fast each different test material melts an ice cube AND how the melting of the ice cube effects the test materials temperature.4Experiment Worksheet5uWhat is the room temperature?uMeasure and record the temperature of each material.uMeasure the weight of the material being tested.

3、5th grade: Convert the weight from pounds to kilograms 6th grade: Calculate the mass of the material and compare it to the actual measurement. High school: Compare methods for calculating mass and converting units. I.e., by hand, calculator, spreadsheet, draw 3-dimensionally on a CAD system and meas

4、ure the properties, web (/measures/fulltable.asp), etc. 6uCalculate the area of the ice cube. Discuss: What shape is the ice cube? What is the formula for this shape? What measurements will be needed? How can the necessary measurements be found?7Calculate Area uTrace ice cubeuMea

5、sure chord length: c =uMeasure height: h =Arl c r h12()8Calculate Area uDiscuss the best way to locate the following measurements: Measure angle: = Measure the radius: r =uCalculate l Arl c r h12()lr001745.9To Locate Center of CircleuRotate ice cube, overlapping the curved portion of the ice cube, a

6、nd trace it again.uFold the circle in quarters to locate center or use a compass.10uArea answers. Give your results to your teacher. Break into small groups and compare answers. Come up with one answer per group.uCompare group answers.uUsing the initial readings, calculate the average.uCompare the a

7、verage to the group answers.uThe teacher will use this answer to calculate the volume of the ice cube.11uPlace the ice cube, side down, on the material.uTime from the placement to completely melted.uStudents discuss: Why is the ice cube melting? What is happening? How is it changing form? Where does

8、 the heat come from?12uRecord: the finish time temperature at the center of the puddle outside edge of the plateuShare data with other groups.13Summary of First Experiment u Where did the heat come from to melt each ice cube (from the test material or from the surrounding air) ?u What makes one test

9、 material faster at melting the ice cube than another ?u Why did the ice cubes move ?uLevel of answers will depend on grade level.14ThermodynamicsuGreek words describe early forms of thermodynamics Therme (heat) Dynamics (power)uToday it covers a wider spectrum of energy and energy transformation I.

10、e., space shuttle to refrigeration15ThermodynamicsuIs the interaction between energy and matter and it is everywhere Hair dryers and heat guns, irons, furnace, air conditioners, hot water tanks, etc. Also must be considered when designing computers, automobile engines, VCRs, CD players, dimmer switc

11、hes, etc.uWhat happens if a hair dryer gets too hot? a computer gets too hot?165th GradeuCalculate DT (Delta Time - change in temperature of the material being tested.) (Tfinal - Tinitial)uCompare student DT results to calculated DT, supplied by the teacher, in a line graph on graph paper or using a

12、 spreadsheet. Discuss the results175th Grade cont.uCompare the amount of heat (Q) each material has available to the amount of heat required to melt the ice cube in a combination bar/line graph. (Data supplied by the teacher) Which material(s) did not have enough heat available to melt the ice cube?

13、 What can be done to increase the available heat?uDo you see any correlations between the two graphs?18SummaryuWhat test material was the best at melting ice cubes ?uDid the color seem to effect the performance ?uWhy would an ice cube melt, even if the test material did not have enough energy to do

14、it ? 19ThermodynamicsuTherefore, different materials are used to the transfer heat I.e., the material in the computer chip in the electric radio alarm clock is used to help keep the chip from overheating. 20Miracle ThawuIs it really a miracle?21Suggestions for Higher GradesuComplete 5th grade level

15、mathematics, graphs, etc., only have the students calculate: The volume and mass of the ice cube. The amount of heat generated by each material. How long a specific material will take to melt an ice cube.uCalculate the volume and mass of the material being tested, and compared to actual measured wei

16、ght.uDiscuss heat transfer in more depth.22Suggestions for Higher Grades cont.uCreate an interactive animated computer program that demonstrates the experiment. Example: :7009/simple_machines/ 23Additional ExercisesuCompare the same material with different masses.uCompare

17、different materials with the same mass. uConduct a web search of items that use heat sinks.uExamples:Library of Thermodynamics Arizona State Univ. /lib/noble/physics/thermo.htmHeating system (heat pipe sinks) and fanshttp:/www.kita.or.kr/catalog/cheil/index.htmlLaptops http:/ http:/

18、www.web_ http:/ http:/ Fun 25Additional slides for advanced grades26THERMODYNAMICSu The science of energy (or its ability to cause changes), andu The relationships among the properties of matter.u HEAT, Q, is the form of energy which melted our ice cubes.u In the SI system, we measure Q in Joules.27

19、THERMODYNAMICSSome important material properties:u m is the mass of the material (kg)u V is the volume (m3)u r is the density (kg/m3)u C is the specific heat (J/kg-oC)28Some Material PropertiesSpecificThermalDensityHeatConductivityMaterial(kg/m3)(J/kg-oC)(W/m-oC)Steel7,85043460Iron7,87044773Aluminum

20、2,770875177Copper8,930385401Lead11,34012935Pyrex Glass2,2258351.4Brick1,9208350.72Pine Wood6402,8050.15Plywood5451,2150.12Ice (near 0oC)9202,0401.88Water (near 0oC)1,0004,2300.57Latent Heat of Fusion for Solid/Liquid Water: 333,700 J/kg29THERMODYNAMICSu For a solid, Q = m C DT u This is the amount o

21、f heat corresponding to a change in temperatureu If you dont know the mass, calculate it from: m = r Vu DT is the change in temperature,(Tfinal - Tinitial)30How much heat does it take to melt one of our ice cubes ?u If the ice cube is at 0oC,u“Latent Heat of Fusion” (amount of energy needed to go fr

22、om solid to liquid states. u For water, that is 333,700 Joules/kg.u If our ice cube is 0.01 kg, the heat required is 3,337 Joules.31Do we have enough energy in our test materials to do that ?Example: uA 0.5 kg. chunk of steel, starting at 22oC, releases 3255 Joules of heat when it is cooled to 7oC.u

23、 Q = m C DT = (0.5 kg)(434 Joules/kg-oC)(22-7 oC) = 3255 Joulesu3337 Joules is needed, therefore, there isnt enough heat to melt the ice cube32Conservation of EnergyBetter yet, we can solve for the final temperature of the steel to melt the ice:DD QmCJouleskgJouleskgCCTTTCCoofinalinitialoo3337054341

24、538221538662( .)().33Conservation of Energyu A 0.5 kg block of steelu Cools from room temperature (22oC) to 6.62oC u Gives up enough heat to melt a 0.01 kg ice cube.34Heat Transfer is the flow of energy which happens when a difference in temperature exists. can happen between two bodies or even with

25、in a single body.u What was the difference in temperature between our ice cubes and our test materials ?35CONDUCTIONu Heat flows through a material from molecule-to-molecule.u Fouriers Law:QkATxDD36Fouriers Lawu Q is the heat transfer rateu k is a material property, thermal conductivityu A is the area which heat f