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Melting Ice Cubes aka. Thermodynamics and Heat Transfer HIGH ASPIRATIONS Created by: Dave Johnson Kathy Holliday-Darr Miracle Thaw Is it really a miracle? Let’s check it out… Melting Ice Cubes: “Icebreaker” J First experiment objective:

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Melting ice cubes aka thermodynamics and heat transfer l.jpg

Melting Ice Cubesaka. Thermodynamics and Heat Transfer

HIGH ASPIRATIONS

Created by:

Dave Johnson

Kathy Holliday-Darr


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Miracle Thaw

  • Is it really a miracle?

  • Let’s check it out…


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Melting Ice Cubes: “Icebreaker” J

First experiment objective:

Determine how fast each different test material melts an ice cube AND how the melting of the ice cube effects the test material’s temperature.

  • Establish teams and have them create a company name

  • Run first experiment



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  • 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.


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  • 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?


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Calculate Area

  • Trace ice cube

  • Measure chord length: c =

  • Measure height: h =


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Calculate Area

  • Discuss the best way to locate the following measurements:

    • Measure angle: α =

    • Measure the radius: r =

  • Calculate l


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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.


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  • 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.


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  • Record:

    • the finish time

    • temperature at the center of the puddle

    • outside edge of the plate

  • Share data with other groups.


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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.


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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


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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?


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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


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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?


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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 ?


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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.


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Miracle Thaw

  • Is it really a miracle?


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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.


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Suggestions for Higher Gradescon’t.

  • Create an interactive animated computer program that demonstrates the experiment.

    • Example:

    • http://socrates.berkeley.edu:7009/simple_machines/


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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




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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.


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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)



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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)


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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.


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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


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Conservation of Energy

Better yet, we can solve for the final temperature of the steel to melt the ice:


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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.


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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 ?


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    CONDUCTION

    • Heat flows through a material from molecule-to-molecule.

    • Fourier’s Law:


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    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


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    Fourier’s Law

    How do you make the ice cubes melt faster ?

    What do the terms in Fourier’s Law show us ?

    Which variables can you control ?


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    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 ?


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    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 ?


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    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.


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