Melting Ice Cubes aka. Thermodynamics and Heat Transfer

1. 1 Melting Ice Cubesaka. Thermodynamics and Heat Transfer

2. 2 Miracle Thaw Is it really a miracle? Let�s check it out�

3. 3 Melting Ice Cubes: �Icebreaker� J Establish teams and have them create a company name Run first experiment

4. 4 Experiment Worksheet

5. 5 What is the room temperature? Measure and record the temperature of each material. Measure the weight of the material being tested. 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 measure the properties, web (http://n93.cs.fiu.edu/measures/fulltable.asp), etc.

6. 6 Calculate 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?

7. 7 Calculate Area Trace ice cube Measure chord length: c = Measure height: h =

8. 8 Calculate Area Discuss the best way to locate the following measurements: Measure angle: a = Measure the radius: r = Calculate l

9. 9 To Locate Center of Circle Rotate ice cube, overlapping the curved portion of the ice cube, and trace it again. Fold the circle in quarters to locate center or use a compass.

10. 10 Area answers. Give your results to your teacher. Break into small groups and compare answers. Come up with one answer per group. Compare group answers. Using the initial readings, calculate the average. Compare the average to the group answers. The teacher will use this answer to calculate the volume of the ice cube.

11. 11 Place the ice cube, side down, on the material. Time from the placement to completely melted. Students discuss: Why is the ice cube melting? What is happening? How is it changing form? Where does the heat come from?

12. 12 Record: the finish time temperature at the center of the puddle outside edge of the plate Share data with other groups.

13. 13 Summary of First Experiment Where did the heat come from to melt each ice cube (from the test material or from the surrounding air) ? What makes one test material faster at melting the ice cube than another ? Why did the ice cubes move ? Level of answers will depend on grade level.

14. 14 Thermodynamics Greek words describe early forms of thermodynamics Therme (heat) Dynamics (power) Today it covers a wider spectrum of energy and energy transformation I.e., space shuttle to refrigeration

15. 15 Thermodynamics Is 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 switches, etc. What happens if a hair dryer gets too hot? a computer gets too hot?

16. 16 5th Grade Calculate DT (Delta Time - change in temperature of the material being tested.) (Tfinal - Tinitial) Compare student DT results to calculated DT, supplied by the teacher, in a line graph on graph paper or using a spreadsheet. Discuss the results

17. 17 5th Grade con�t. Compare 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? What can be done to increase the available heat? Do you see any correlations between the two graphs?

18. 18 Summary What test material was the best at melting ice cubes ? Did the color seem to effect the performance ? Why would an ice cube melt, even if the test material did not have enough energy to do it ?

19. 19 Thermodynamics Therefore, 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.

20. 20 Miracle Thaw Is it really a miracle?

21. 21 Suggestions for Higher Grades Complete 5th grade level 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. Calculate the volume and mass of the material being tested, and compared to actual measured weight. Discuss heat transfer in more depth.

22. 22 Suggestions for Higher Grades con�t. Create an interactive animated computer program that demonstrates the experiment. Example: http://socrates.berkeley.edu:7009/simple_machines/

23. 23 Additional Exercises Compare the same material with different masses. Compare different materials with the same mass. Conduct a web search of items that use heat sinks. Examples: Library of Thermodynamics Arizona State Univ. http://www.asu.edu/lib/noble/physics/thermo.htm Heating system (heat pipe sinks) and fans http://www.kita.or.kr/catalog/cheil/index.html Laptops http://www.indek.com/heatpipe/hp_app.htm Computers http://www.thermalloy.com/catalog/htm/dhs57.htm http://www.web_tronics.com/webtronics/heatredmouns.html http://www.heatsink.com/ http://www.execpc.com/industrialelectronics/wakefld/wakepg19.html http://www.marlow.com/d_heat.htm Dimmer http://home.swbell.net/evansjim/MyHomeRepair/DimmerSwitch.htm http://www.thermalloy.com/catalog/htm/eprof41b.htm

24. 24 Have Fun

25. 25 Additional slides for advanced grades

26. 26 THERMODYNAMICS The science of energy (or its ability to cause changes), and The relationships among the properties of matter. HEAT, Q, is the form of energy which melted our ice cubes. In the SI system, we measure Q in Joules.

27. 27 THERMODYNAMICS Some important material properties: m is the mass of the material (kg) V is the volume (m3) r is the density (kg/m3) C is the specific heat (J/kg-oC)

28. 28 Some Material Properties

29. 29 THERMODYNAMICS For a solid, Q = m C DT This is the amount of heat corresponding to a change in temperature If you don�t know the mass, calculate it from: m = r V DT is the change in temperature, (Tfinal - Tinitial)

30. 30 How much heat does it take to melt one of our ice cubes ? If the ice cube is at 0oC, �Latent Heat of Fusion� (amount of energy needed to go from solid to liquid states. For water, that is 333,700 Joules/kg. If our ice cube is 0.01 kg, the heat required is 3,337 Joules. Ice starts at 0�C Change of phase is from solid to liquid - for H20 that is 333,7000 Juoles/kg 1 kg Ice cube needs 333,700 J/kg to melt it A .01 kg ice cube needs 3,337 to melt it Ice starts at 0�C Change of phase is from solid to liquid - for H20 that is 333,7000 Juoles/kg 1 kg Ice cube needs 333,700 J/kg to melt it A .01 kg ice cube needs 3,337 to melt it

31. 31 Do we have enough energy in our test materials to do that ? Example: A 0.5 kg. chunk of steel, starting at 22oC, releases 3255 Joules of heat when it is cooled to 7oC. Q = m C DT = (0.5 kg)(434 Joules/kg-oC)(22-7 oC) = 3255 Joules 3337 Joules is needed, therefore, there isn�t enough heat to melt the ice cube Q = (.5kg) (434J/kgC)(22-7�C) =3255 Joules Q = (.5kg) (434J/kgC)(22-7�C) =3255 Joules

32. 32 Conservation of Energy Better yet, we can solve for the final temperature of the steel to melt the ice: Temperature must drop 15.38 �C in order to melt the ice cube. Therefore if the initial temperature of the material is 22 �C, it must drop to 6.62 �C in order to melt the ice cube.Temperature must drop 15.38 �C in order to melt the ice cube. Therefore if the initial temperature of the material is 22 �C, it must drop to 6.62 �C in order to melt the ice cube.

33. 33 Conservation of Energy A 0.5 kg block of steel Cools from room temperature (22oC) to 6.62oC Gives up enough heat to melt a 0.01 kg ice cube.

34. 34 Heat Transfer is the flow of energy which happens when a difference in temperature exists. can happen between two bodies or even within a single body. What was the difference in temperature between our ice cubes and our test materials ?

35. 35 CONDUCTION Heat flows through a material from molecule-to-molecule. Fourier�s Law:

36. 36 Fourier�s Law Q is the heat transfer rate k is a material property, thermal conductivity A is the area which heat flows through DT is the temperature difference Dx is the distance the heat must travel

37. 37 How do you make the ice cubes melt faster ? What do the terms in Fourier�s Law show us ? Which variables can you control ? You can increase Q by changing: Delta T � make the plate hotter A � increase the area k � you can�t change the density, but you can change the material Delta X � no, you can�t change the distance the You can increase Q by changing: Delta T � make the plate hotter A � increase the area k � you can�t change the density, but you can change the material Delta X � no, you can�t change the distance the

38. 38 Fourier�s Law Fourier�s Law tells us how fast heat will flow. Do we know if there is enough energy available in our test materials to melt our ice cube ?

39. 39 Fourier�s Law The rate of heat flow is: The steel block cools from 22oC to 6.62oC in melting the ice which is 0oC. As that happens, the value of DT decreases. Therefore, the rate of heat transfer to the ice decreases. How can we increase the rate for a given material ?

40. 40 GO TO WORK !!! Determine: if your test materials have enough heat to melt an ice cube. Measure the rate (time) of heat transfer. Tabulate your experiment data.