Heat loss - Sample Essay
To investigate how the three types of heat transfers affects heat loss and ways to stop this from happening and applying this to a model house. Plan My partner and I chose to investigate convection, whilst the rest of the group were to investigate either radiation or conduction. For convection particularly, I took two identical beakers. I then took a piece of card and cur out a circle which fit on the beaker. I cut a small circle in the centre to fit a thermometer in.
Before putting a lid on top, my partner and I poured 200ml of hot water from a kettle in the two beakers (I measured at eye-level for accuracy); one with the lid and the one without which was acting as a control. We were then ready to begin the experiment. We took a stop watch and timed up to five minutes, recording the temperature after every one minute. We then repeated the experiment once more to make our results reliable. After doing all that, we did a separate experiment, using two different materials as lids. This was in order to see if different materials are better at reducing heat than others.
In order to make this a fair test, we had to have constants and only one variable. We made sure that the size beaker was the same, that the volume of water was the same, that we used the same equipment for both beakers and the only variable was that one had a lid and the other never. We did all this so that the data we received was valid. We only had one variable as we had to differentiate between the two beakers so that we could compare the heat losses between both of them. In other words, we wanted to see if having a lid really made a difference and to see the amount of heat loss there would be without a lid.
Equipment Use Beaker For the experiment Thermometer To check the temperature Lid To see how it affects convection Safety mat To keep things safe and so that if water were to spill then it would just go on the mat. Stop watch To time the experiment Prediction I predict that having a lid/ covering the top of the beaker prevents/reduces heat transfer. This is because; convection is a heat transfer in which currents flow from a warm surface to a colder one. The direction of its movement is vertical in which warm air rises and cool air sinks.
The way in which this is done by is that the atoms in a liquid, when heated, move around much faster, colliding with the other atoms and making them have more kinetic energy. They then move in a vertical motion rising above the surface. As they are moving further and further away from the heat, they become cool again and so the atoms become further away like before. This makes them sink. Having a lid means that the warm air won’t rise and escape into the atmosphere. Having something to cover the beaker reduces the chances of heat escaping and therefore reduces heat loss and prevents convection from happening.
Radiation Radiation is the heat transfer in which energy is radiated or transmitted in the form of rays, waves or particles. The most common type is Ifra-red radiation; the type which the Sun has. I predict that having a shiny surface or covering the beaker with something shiny, will prevent radiation. This is because, as the heat in the object, in this case water, is trying to escape via radiation, this very same energy hits the shiny surface and reflects back inside the beaker. This means that radiation is reduced. Conduction
Conduction is the final heat transfer in which a substance transfers heat energy to another substance by direct contact of atoms or molecules. I predict that having a sponge or foam around the beaker will prevent conduction. Reasons for this are that, a sponge or foam contains trapped air. This means that it cannot escape. Air is known to be a very poor conductor of heat. This prevents conduction and so reduces the amount of heat loss. The number of observations I will take will be five as I will be recording the temperature after every one minute up to five minutes.
Results Time Temperature for beaker with lid (in degrees Celsius) Temperature for beaker without lid — Control Here are the first set of results for convection: Here is our repeated ones: Time Temperature for beaker with lid (in degrees Celsius) Temperature for beaker without lid — Control Average: Time Temperature for beaker with lid (in degrees Celsius) Temperature for beaker without lid — C 66 Results from the other groups:
For radiation Temperature ( In degrees Celsius) Time Both Control Outside InsidFor conduction – with thermometer Time Insulated Non-insulated 1 Here are the results of the other experiment we did in order to see which material is better at preventing convection. Time Card Aluminium foil 1 Analysis.
From my results, I can conclude that having something to cover the beaker affects and reduces convection in that having a lid allows the contents of the beaker, in this case water, to still be warm. I can also say that the material the lid is made from does make a difference in reducing convection. From my results, it is obvious that the aluminium foil is better at preventing convection than the card. I can also see that my graph also interprets this in that the line of best fit for the beaker with card is above the line of best fit for the one without. Also the one with a lid ends at a higher temperature than the one without.
I notice a pattern in both which is that both lines of best fit are curved; a smooth curve. Between the first and second minute, the temperature decreased profusely. First it was 83i?? C for the beaker with card and 82i?? C for the one without and at the second minute it was 78i?? C for the card one and 75i?? C for the one without. You can tell from the numbers that it had decreased in high amounts. You can also tell this by looking at the graph. After that, the rate in which the temperature decreases is lower and it decreases slower as the time increases. This can be said for both; the one with the card and the one without.
I can see that my results match my prediction in that having something to cover the beaker reduces and prevents convection from happening and so reduces heat loss. As was said earlier, as the heated atoms of the water tried to escape into the atmosphere, they had nowhere to go, because the lid was doing its job and preventing the heat from escaping and so the heat had nowhere else to go besides back in its container. From the group results, I can also see that my prediction was also correct in that matter. Having an insulator around the beaker prevents conduction and having a shiny surface prevents radiation.
My predictions were right in all three cases. I can now use all this information in my model house and suggest ways to prevent the heat transfers in a house. One way could be to consider having metal curtains of some sort to prevent radiation so that any heat which hits the surface reflects back into the house. Another thing could be to use foam or any other material which contains trapped air and put it between a set of walls. This prevents conduction as air is a poor conductor of heat. The same could be done with the roof and a more suitable material may be considered to be used to reduce convection.
These are just some ways to prevent the heat transfers, but there are plenty. Evaluation I thought my planning was quite well done; my predictions were correct in that aspect. My results also represented my predictions and from all the results recorded, my predictions were correct in all areas too. I thought I recorded them well, however I think it would have been better and more accurate and reliable if I chose to do a slightly bigger range of observations and done it up to 10 minutes instead. I could also have used data loggers rather than thermometers to make the plan more accurate and reliable.
Those are just several ways, but I think that the experiment wasn’t entirely a disaster. My accuracy overall was not so bad; I measured at eye-level, when I had to pour the 200ml of hot water, but there’s still more areas needed to be improved in that aspect and also when we had to use the thermometer, I measured at eye-level there. There wasn’t really any anomalous result as all the recorded results, which were plotted on the graph, were either on or just close to the line of best fit. However, I noticed something strange in the group’s work.
For conduction, I noticed that in the last two minutes, the temperature jumped from 75i?? C to 64i?? c. I thought that it must have been recorded wrong. I can understand that happening in the first two minutes, but it seems slightly strange and my group must have surely recorded wrong, which makes it look unreliable. I think that the evidence is sufficient for a firm conclusion and that insulating, having a lid on top of and having a shiny surface does affect the heat transfers in that in all three areas, heat loss is reduced. I know this as this is what my graph and not only have my results showed me.
Maybe having a lid, insulation or having a shiny surface doesn’t entirely stop heat loss, but at least it reduces it bit by bit. A way to extend my enquiry would be either to continue with seeing which material is best at reducing and preventing convection or to do another experiment in which there are two beakers; one used as a control and the other one which has all three methods at preventing all three heat transfers; aluminium foil, insulation and a lid. This way we could see how that affects the heat loss and if some materials are better at doing their job than others.