Investigation into the U-Values of Different Materials

The aim of this investigation is to compare the U-values given off by conductors of different materials.

The U-value for any specified heat conductor is the heat energy lost per second through the conductor per square metre when there is a temperature difference of 1�c between its surfaces.

FAIR TEST:

* I must have equal amounts of water in each container. - This ensures the same amount of water will be heated up. To do this I will need to measure each one accurately.

* I must make sure each material covers the same surface of the metal container.- This ensures the 'temperature given off' is carried out fairly.

* I must start measuring the temperature of each container at the same time. - This means the starting temperature will be the same so that each experiment begins fairly.

* I must place the thermometer just outside the containers. - This ensures I am reading the temperature of what is being given off and NOT the outside temperature.

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EQUIPMENT:

1. Water

2. Conducting Materials : -Artificial fur

-Foil (aluminium)

-Cotton wool (with cello tape)

-Carpet

-Copper Calorimeter on its own

3. Copper Calorimeter X 4

4. Thermometer

5. Stop-clock

6. Kettle

7. Measuring beaker

8. Weighing machine

9. Clamps X 2

METHOD:

1. Each indicator will be weighed in the beginning in kg.

2. Boiled water will be poured into the measuring beaker.

3. 225 ml of water will be poured into each container.

4. Each container will have a thermometer inside to measure the water's temperature and one touching the outside of the calorimeter to measure the temperature lost by each container.

5. The clamps will secure the thermometers.

6. The temperatures will be measured before the stop-clock has started

7. Once these results are recorded, I will start the stop-clock.

8. After each minute, I will record the readings until 15 minutes have passed.

PREDICTION:

From my previous knowledge of science, I know that good insulators have low U-values.

From the above indicators mentioned in the equipment section, I predict the fur and carpet will provide the lowest U-values. This is because fur is usually used as a material to trap heat e.g clothes, quilts etc. From previous gained scientific knowledge I know it traps hot air through a conventional circulation under the layers of fur similar to human hair.

I predict the copper calorimeter will provide the lowest U-values. This is because the container will have no form of insulation and will therefore let out the most energy.

Here is the order of insulation:

1. Fur

2. Carpet

3. Cotton wool

4. Aluminium

5. Copper

SAFETY PRECAUTIONS:

To ensure a safe test I will:

* Make sure I carefully handle the boiling water so nobody is burnt.

* Hold the container carefully, as it will be extremely hot.

* Make sure the equipment is securely stable.

COLLECTION OF RESULTS:

I will have to collect 5 sets for each of the five containers, which in total is 25. I will need to find out for each beaker:

1. Specific Heat Capacity of water.

2. Energy loss through the material.

3. Rate of energy lost through the material.

4. Average temperature difference for each material

5. The U-value for each experiment.

I think I will need to repeat the experiment again to improve the accuracy of the first set of results. I should also double-check the measurements of the weight and surface area.

This could be because I may not have carried out the first results in a fair way. With the second set of results, I could produce an average.

In addition, I could use another person's results to back up mine.

The range of results would be the timing form 0-15mins and the S.H.C of the water being 4200J/(kg�c) constantly for all indicators.

PREVIOUS EXPERIMENT

I have chosen to use the textbook stated 'Specific Heat Capacity', as my earlier experiment on 'Specific Heat Capacity' does not show an accurate enough reading.

In addition, I will not use the voltage and amperage as I know it is not necessary in this experiment from the textbook. (Look at graph please)

Obtaining evidence

This experiment is about which different materials out of the previously mentioned indicators are the best and worst insulator (material that traps in heat). I will find this out by working out the U-values for each indicator.

I will need to keep the same amount of water in each calorimeter. This ensures that the mass therefore the whole experiment will not be affected. Read also surface area and heat loss experiment

I will need to place the thermometers in the same positions every time. This ensures I am reading the energy being lost and NOT the outside room temperature.

DIAGRAM OF EXPERIMENT

I have collected my results (see TABLE OF RESULTS please) from the above experiment and calculated the U-values using the following formulas.

1. Formula to calculate 'Energy Lost':

2. Formula to calculate 'Rate of Energy Lost':

3. Formula to calculate 'U-Value'

U-Value =

Table of Answers

Energy Lost (J)

Rate of Energy Lost (secs)

U-Value

Cotton

15726.942

17.47438

8.4

Carpet

17772.72

19.74746666

11.1

Copper

27354.7008

30.39412

18.5

Fur

17898.804

19.88756

7.6

Foil

25221.042

28.02338

21.4

*Lowest U-value highlighted in green

*Highest U-value highlighted in red

Analysing Evidence and Drawing Conclusions

This line graph shows that the copper on its own had the heat inside reduce the most.

Cotton had the least heat reduced (see black line on graph).

As can be seen Fur has the lowest U-Value (7.6), which means it is the best insulator.

Foil has the highest U-value (21.4), making it the worst insulator.

CONCLUSION

The order of insulation is:

1. Fur

2. Cotton

3. Carpet

4. Copper

5. Foil

My prediction of Fur being the best insulator was correct as the above ranking shows. As I mentioned in my plan, fur being the thickest meant that it would be the best insulator. The furs trap the hot air. The hot air flows in convection currents between the furs and copper.

I predicted Copper on its own would have the highest U-value because it will have no material as an insulator. However, my results disagreed with this prediction as Foil had the highest U-value. This meant the copper calorimeter on its own was a better insulator than the calorimeter with the foil indicator.

Evaluating Evidence

I think this method of carrying the U-value experiment was a good way. This method provides accurate results

If I were to repeat the experiment, I would make sure I repeated ALL measurements again, such as the weight of the calorimeters with water, surface area etc. This would improve the accuracy of my results. I would also add another 5 minutes to my time range so that I have a bigger range of data. A bigger range provides better results. In addition to this, I would make sure the material around the calorimeter would cover the calorimeter properly.

ANOMALIES

The results, which I find, did not fit in my results was that foil had a higher U-value than the copper calorimeter alone.

I also thought that carpet would have a lower U-value than cotton wool because it was a much thicker material than cotton wool. Carpet is used as an insulator on floors to keep the heat from escaping through the floorboards.

I think the reason for the copper calorimeter being a better insulator than the foil indicator could be due to the measurements of surface area being incorrect. If you see on the result's table, it shows the foil indicator has a smaller surface area. This could be due to a smaller calorimeter being used for the foil. As such this should not affect the results because, everything would be smaller in the process. However, the possibility of the calorimeter having a smaller amount of water could be the cause of this. Foil being aluminium means it is a metal. Aluminium has a specific heat capacity of approximately 960 J/(kg�c). This information is from a textbook. Therefore, this specific heat capacity combined with the specific heat capacity of water could explain the outcome of the foil indicator of having the highest U-value (the best conductor)

As for the cotton wool, being a better insulator than the carpet could be due to the fact the carpet was not properly covered over the whole of the calorimeter. This in effect would mean heat energy could escape through the exposed part quicker. In addition to this, the cello tape on the cotton wool indicator could have trapped air bubbles. These air bubbles have trapped hot air, which would improve the insulation of the cotton wool indicator.

OTHER EXPERIMENTS

If I had enough time, I would find the specific heat capacity for each calorimeter. This would improve the accuracy of my results when using the formulas.