How to Stay Hot and Keep Your Cool

With Summer around the corner I thought I would post my first DIY science experiment. This was easily done on a low budget and I can't wait to do this in the classroom! If you don't want results/spoilers stop reading now and go here!

Abstract (TLDR - SPOILERS)

This study aims to prove through the theory of conservation of energy that Styrofoam is a superior insulator and is better at restricting the transfer of heat than cotton, and aluminium foil. This study also aims to prove the aluminium foil is a superior conductor than Styrofoam and cotton because heat energy can transfer through it more easily than the other materials. To test this hypothesis I constructed a test observing the time it took for a 17 ml cup of warm water to freeze in a freezer. An additional cup of water with no insulator was added as a control group. The next test would take the complete frozen ice in the cups and submerge them in warm water and record how long it would take for them to completely melt. The results showed that our original hypothesis was partly correct as Styrofoam was a good insulator, but cotton outperformed it in both tests. We also discovered that aluminium foil is the best conductor of the three.

Introduction

The purpose of this study is to use the principle of conservation of energy to determine which materials would be best to keep cold things from warming up (insulator) and warm things from cooling down (conductor). By freezing warm tap water the best would lose energy slower thus freezing at slower times. Once frozen the best conductor would then melt faster once heat was applied due to its ability for heat to transfer past it. This field of study is important to us because in our daily lives we need to construct several devices to maintain a range of temperatures. Whether it be cooling a processor in our electronic devices or keeping our coffee and tea at acceptable levels, we should be able to perform tests to find suitable properties for a specific purpose.

Method

1. First prepare the insulators and conductors by stretching the cotton balls in a thinner filling and ripping the Styrofoam and aluminium foil into smaller pieces anywhere from 2 to 5 cm.

2. Then place the materials into the transparent large cups and to ensure fair insulation the contents of the cup should be no be visible from all sides (excluding the open top). Label the cups according to their material.

3. Fill and place a small cup (17 ml) of warm tap water into a larger cups and then seal the top of the cup with a transparent plastic seal and a rubber band.

4. In addition to the cups with insulated materials, form a control group by placing another 17 ml cup into a large cup without an insulator material (air).

5. After sealing top of all four large cups, place each in the freezer at the same time. Set timer to go off every 15 minutes.

6. Observe the cups every 15 minutes to record which of the four test samples formed ice first.

7. Once all four samples are solid frozen the cups would be removed from the freezer and placed on baking sheet.

8. Place a weight (a heavy book) on top of the cups to keep them from floating to the surface as they will be submerged in a cooking pot of warm tap water. Fill the pot with warm water and place the cups in side.

9. Observe the cup for changes every 2-3 minutes to record which of the four test samples showed signs of melting first.

Data forms for Students

Hypothesis

Using my prior knowledge of insulators and conductors I believed the best insulator would be the Styrofoam and the best conductor will be the aluminium foil. I selected Styrofoam as the best insulator due to the frequency I see them being used as coolers on fishing trips or at the beach. I believe that cotton, air, and aluminium, in that order are poor insulators in comparison to the foam.

I selected aluminium foil as the best conductor as I find that when cooking, wrapping objects in aluminium foil allows for heat to be transfers quickly from the oven to the food. I believe air, cotton, Styrofoam in that order are poor conductors in comparison to the foam.

a. The warm water of the aluminium foil freezes the fastest because the heat energy from the warm water will easily transfer from the small cup into the cold air of the freezer. Additionally the Styrofoam container would freezes the slowest as its properties allow it to heat energy from the warm water to pass through the insulation.

b. To reinforce my hypothesis the frozen ice will have melted slower in Styrofoam insulator as the warm energy (outside) is not able to affect the internal temperatures of the cup as quickly due to its inability to pass energy through the material. The ice in the aluminum foil cup should then melt fast because as a better conductor the energy from outside the cup should transfer into the ice quicker.

Results

The result of our first test indicated that the order in which the materials showed signs of freezing. The graph A represents the state of the warm water placed in the freezer using 15 minute interval observations. The fastest freezing water was both the Control Group and Aluminium Foil, while Cotton and Styrofoam were the slowest.

The result of our second test indicated the order in which the materials showed signs of melting. The graph B represents the state of the ice placed in the warm water using 2 minute interval observations. The fastest melting water was the Aluminium Foil, then the control group, while Cotton and Styrofoam were tied for slowest melting taking 16 minute

Discussion

The principle of energy convection were in affect as the transfer of heat energy differed depending on the materials being used. This relates to us in our lives as we often rely on this principle when designing devices that need to control temperature such as a food cooler or a coffee mug. The heat energy was unable to pass through the materials that were better insulators such as Styrofoam and cotton while poor insulators like aluminium and our control group (air) were not as suitable. We did not anticipate that cotton would outperform the Styrofoam. I understood cotton is often used in winter clothing and inside lunch box packs, but alternatives like fur and feathers seem to work much better.

We also concluded that the best conductor was aluminium foil because when heat was applied it was the fastest to show signs of losing energy through melting. Although it was slower than our control group (air as insulator material) the results show that Styrofoam and cotton proved to better insulators by a 2 and 4 minute margins.

The results proved that our hypothesis was partially correct in that Styrofoam is a good insulator, but we did not predict that cotton would outperform it. The best conductor out of the test was aluminum which froze just as fast as our control group and completely melted before the other two when submerged in water.

Possible Error or Variability

I believe the quality, size, and the technique I used to pack the cotton and Styrofoam may have affected the outcome of the results. The cotton balls were still thick after I stretched them and began filling around the warm water cup. I also failed to check what temperature was considered warm before doing the second test. I used my hand to test the water as a gauge instead of a thermometer and I also noticed that the temperature of the warm water began to drop. For next time I run the experiment I will bring a thermometer to record the temperature of the freezer and the warm water. For the second test I may also want to use a constant heat source such as a heat lamp to better emulate the sun or warm weather,

Bibliography

https://www.teachengineering.org/activities/view/the_best_insulator