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Melting Ice Cubes aka. Thermodynamics and Heat TransferPowerPoint Presentation

Melting Ice Cubes aka. Thermodynamics and Heat Transfer

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Melting Ice Cubes aka. Thermodynamics and Heat Transfer

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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:

Melting Ice Cubes aka. Thermodynamics and Heat Transfer

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Melting Ice Cubesaka. Thermodynamics and Heat Transfer

HIGH ASPIRATIONS

Created by:

Dave Johnson

Kathy Holliday-Darr

- Is it really a miracle?
- Let’s check it out…

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

- 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.

- 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?

- Discuss:

- Trace ice cube
- Measure chord length: c =
- Measure height: h =

- Discuss the best way to locate the following measurements:
- Measure angle: α =
- Measure the radius: r =

- Calculate l

- 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.

- 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.

- 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?

- Record:
- the finish time
- temperature at the center of the puddle
- outside edge of the plate

- Share data with other groups.

- 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.

- 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

- 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?

- 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

- 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?

- 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 ?

- 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.

- Is it really a miracle?

- 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.

- Create an interactive animated computer program that demonstrates the experiment.
- Example:
- http://socrates.berkeley.edu:7009/simple_machines/

- 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

- Library of Thermodynamics Arizona State Univ.

Additional slides for advanced grades

- 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.

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)

- 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)

- 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.

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

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

- 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.

- is the flow of energy which happens when a difference in temperature exists.
- can happen between two bodies or even within a single body.

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

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 ?

- 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 ?

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 ?

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