There are many different types of material that could be used, which are fibrous. The insulation will have to be used throughout the experiment and will have to be of uniform thickness. This will prevent any of the reading being biased or misleading.
An insulator that would stop mostly conduction and convection would be the most suitable material to use. This is because the insulation in the walls and ceiling is of the same nature. There are several problems with using cotton wool, the most troublesome of which is that it would be difficult to get the wool of the same thickness throughout the insulation. There are a couple of options: If it possible, it would be beneficial to buy strips of cotton wool that is uniform in thickness, or to use a set mass of cotton wool.
The other option to consider would be to use a fibrous fabric that would be of consistent thickness. This fabric – such as is found in a tie or t-shirt – would be inexpensive and easy to use. It would be of much help to us.
For this reason I have decided to use a fabric of regular thickness if possible.
Representation of the house
There are several options as to which material we could make the house from. We could use: A polystyrene cup with a lid or a glass beaker and a petri dish as the lid.
We analysed both.
The Polystyrene Cup:
Most cups are made from polystyrene… this is because it is a good insulator. Polystyrene is a material that traps air and air is an insulator. This prevents heat transfer. This is why it is used in hot drinks to keep them hot and in cold drinks to keep them cool.
The polystyrene cup would be a good example of how certain materials are insulators while others can conduct heat away easily. This is not what we want. For this experiment it is my opinion that a beaker that would lose heat quite fast would be necessary.
There are two reasons for this:
- Objects that will lose heat quickly will show a definite cooling curve, even if we are unable to use the more accurate methods of tracking heat loss in a shorter period of time.
- Objects that lose heat quickly will be easier to track when we put insulation in certain places making the experiment quicker and more effective.
The next option was
The Glass Beaker:
The glass beaker seemed a much more fitting option, not only does it lose heat relatively fast, but it is also easy to use obtain. The only problem could be that there is no lid made to fit over the top. WE tried to over come this problem by putting a petri dish over the top, this would prevent a certain amount of heat loss through the top – much like a roof would!
We now knew which material we would use as an insulator and what we would use to represent the house. We needed to detail the experiment to make it a fair test.
We already agreed that water would represent hat air in the home. We decided to do this as; water has a high specific heat capacity that would be easier to monitor than something with a lower SHC!
It would be necessary to have a preliminary test to see how long the water would take to cool etc. We will also need a control, a beaker that had no insulation around it so we can compare results.
We decided that if we heat the water to a temperature higher than 80ºc then let it cool to that temp we will know exactly how many joules of energy are in the water at the start and if we measure the temp at the end we will know how many joules were lost. After the water reaches 80ºc we will take readings at different intervals depending on what results the preliminary test gave. We will wrap cotton wool or another fabric around the beaker in certain places reflecting areas insulated in the home. From this we can plot a cooling curve. In theory the most efficient insulator will have the shallowest cooling curve.
In order for this to be a fair test we will have to test each insulator 3 times to filter anomaly.
This table shows the things that I shall change and the things that I shall keep the same during the experiment:
“What we will do”
- Method - We shall heat the water up to 80ºc and take readings over a 600 second period of time. From this we hope to be able to plot the cooling curves of the averages and conclude whether or not the insulation was.
Safety – To make sure that we are safe as we carry out this investigation, Safety specs will be worn at all times. We shall also avoid carrying hot water large distances and avoid contact with the beaker after the water has been poured away.
I believe that the area that will be most effected by the insulation will be the walls. Be looking at other sources I came across a page in the physics for you book that talked about heat loss in the house. Most heat was lost through the walls then the roof then the floor. I believe that it would be necessary to insulate the walls for this reason. I hope that my investigation will imitate this.
Investigation - Obtaining Evidence
“What we could see” - When the experiments took place we were not able to see much happen. All we could see was the steam trying to leave the top of the beaker.
“Measuring Carefully” – We realised that the convection currents would appear within the beaker, just like with air in the home. We wanted the experiment to be as true to life as possible and I believe that this helped, but, the currents resulted in different temperatures in different areas. At the bottom of the beaker it may have been 60ºC and it may have been 75ºC at the top. So in order to over come this problem we measured from the bottom of the beaker. This was decided as the best way as it would give a more definite cooling cure. The only problem we able to see was that it could result in false readings when it comes to the insulation on the floor.
“Results” – These are results we obtained:
These are the averages:
Here follows a graph of the cooling curves with different insulation areas:
Investigation – Analysis
“What I Have Found Out” – From this investigation I have found out that; each of the curves follow that theory that “Over a period of time heat will be lost until it is the same as the surrounding area.” - Physics For You Text Book.
It is possible to see that heat is lost from all of the beakers this is expected. Heat is lost fastest at the beginning of the experiment and as time continues the heat lost reduces. This is because the surrounding temperature is increasing. The walls retain the most heat and the control lost the most heat in the smallest period.
“What can I obtain from my results?” – From my table of results and my graphs I’m able to come to the conclusion that: Insulation in the walls is the most effective at maintaining heat. I can also assume that insulation is beneficial as it reduced the heat loss. If there were insulation on the roof, floor and walls much more energy would be saved than in the control. I believe that the reason most heat was lost through the walls as they have the highest surface area. This means that there is a larger area for heat to be lost. The insulation is more effective here because of this. If insulation retains 50% of all heat lost in that area then it would be more effective in the walls e.g.:
50% of 100 Joules = 50 Joules – Walls
50% of 80 Joules = 40 Joules – Roof
As you can see, more heat is retained if the insulation retains a percentage of the total heat lost. From this experiment I’m able to state that:
“Most heat is lost from the walls.”
“The most efficient Method of insulation is around the walls.”
“Insulation helps greatly in retaining heat.”
“The experiment performed is accurate and helpful when trying to draw conclusions concerning the effectiveness of insulation.”
“Do my results agree or disagree with my predication?” – The results match my predictions and the textbook well. As time was spent researching predictions I had a strong suspicion that if the experiment was carried out in a professional manner the results would reflect the prediction.
Investigation – Evaluation
Due to professional composure and expansive planning, I believe that the results obtained from this investigation were sufficient to make firm conclusions that can be backed up with quotations from other sources.
Although the investigation was highly successful there are several things I would change if I was to conduct the experiment again there are several things I would do differently.
Firstly I would change the fluid that represented the house. I would not use water as it has a high SHC. This means that it has much energy within it at high temperatures and it would therefore take longer to cool. This is the reason our cooling curves are not as steep as I would like them to be. I could have used a different axis, instead of using 100-0ºC I could have used a graph of 100-65ºc. This would accommodate all results as they all fall in this range and the cooling curve would have appeared much more evident.
If I was to change the fluid that represented the air within the house it would have been essential to use a temperature reader more accurate than a thermometer. It would be much more accurate and there more reliable. The Graphs could have been plotted easier and with more precision.
It may also have been beneficial to work in a room with static air. We were working quite close to a window and therefore the air would be moving and the heat around the beaker would have been dispersed. This could have altered the results slightly but for classroom purposes I believe the results obtained are reliable and I’m therefore satisfied with them.