What Factors Affect The Cooling Of A Liquid

Fair Testing and Other Factors that need to be controlled

There are things that I will need to try and make sure are the same throughout my experiment. These are: -

• Amount of liquid- I will have to make sure that each time I refill the glass beaker I have the same amount of liquid. To do this I will measure it in some measuring apparatus. Each time I will use the same type and size of measuring apparatus, for the same accuracy. To make this even fairer I will simply measure the amount of water in my glass beaker, so I know that it will always be the same.
• Temperature of surroundings- there is not much I can do to control this, but to make sure there is no drastic change, I will stay away from radiators and places in direct sunlight.
• Shape, Colour, Size, Surface Area and Thickness of container- will have to be the same throughout my experiment to keep it fair and to get reliable results. For instance, if I had a different colour container each time I did my experiment it would affect my results. This would be, because instead of reflecting the heat back in, if I had a black container it would absorb the heat. To make sure of this I will use the same container each time.
• Temperature of liquid to start- I will try to keep the around the same. If I cannot keep the temperature the same I will just measure the difference between the two (start and end).
• Type and Density of Liquid- I will keep using the same type of liquid throughout my experiment because some types may loose heat at a different rate than others. I will use water because it is easily available, and it is the same each time.
• Surface container is on- will have to be the same. If for example I was to put it on a foam surface one day, and something different another day, it would affect how much heat is lost. This is due to the surface acting as insulation.
• Lid- I am going to use a lid each time. This should stop a lot of heat reduction through evaporation, which I have already explained in my prediction.
• Time- the time the liquid is left to cool for in the container will have to be the same. If not, then there will be more time for heat to get out therefore making it unfair. The time that the liquid is left in the kettle for will also have to be the same, therefore not allowing it to cool down much before we start to time it. So I will, once the kettle has been boiled, wait for five seconds and then pour directly into the glass beaker.
• Insulation- the type of insulation I am going to be using will have to be the same. Therefore, before my experiment I will cover the glass beaker with 5 layers of insulation, and take one off at a time.
• Thermometer and Data logger- I will put both the thermometer and data logger in the glass beaker at the same time to make sure that there is no difference between the temperature of the water.
• Taking the insulation off- I will have to make sure that when I have finished 5 layers and I take one layer off, I don’t accidentally take two or three off. Also once I have taken a layer off, I will run cold water from a tap on it for 1 minute, this is to ensure that the remaining heat in the glass will not heat up the water when I put it back in.

Range

The range I am using is from 1 layer of insulation to 5 layers of insulation. I think that this will give me conclusive results.

Method

Firstly I will cover my glass beaker with 5 layers of insulation, sticking it down each time with sellotape. Then, once I have finished that, I will clean the kettle, making sure there is no black inside of it, and put 1 litre of water in it. I will then put it on to boil. Meanwhile setting the data logger up and getting the thermometer ready. I will also rinse and dry the glass beaker with cold water before and after use. When the kettle has boiled I will count for five seconds and then pour 400ml of water into the beaker. I will wait for five seconds so that it will be left in the kettle the same amount each time, therefore letting it be the same round about temperature when it gets put in the beaker, leaving it to cool for the same amount of time each time I do it. The data logger and thermometer will both be in the glass beaker through a hole in the lid. Once I have poured the water into the beaker I will put the lid on straight away, then I will time for one minute, to allow the thermometer and data logger time to get to the certain temperature of the water. After the first minute I will start logging he information using the data logger, and write down the starting temperature of the thermometer. I will then leave it for a further five minutes, without any interference. Then stop logging after five minutes and write down the end temperature of the thermometer. Then repeat for each amount of layers, (5, 4, 3, 2, 1, 0). Taking off a layer at a time, and rinsing and drying the glass beaker with cold water before every new experiment. If I have time at the end I will then repeat each amount again to check the validity of my first results; in the case of any major discrepancy between the two results I will repeat that amount again.

Results Table for Thermometer

Results Table for Data Logger

Preliminary Work

I think that my method worked well except for one or two aspects.

• Lid- having a lid was good, except; because it was made of cardboard it started to go soggy. To overcome this I will put a layer of insulation under and on top of the lid. This should help to prevent the lid going soggy.
• Sticking the insulation- because we used sellotape to stick the insulation on the glass beaker, it melted, making it difficult to get layers off, to prevent this from happening we will use a different method of sticking on the insulation.

        

Evaluation

My test was reasonably fair but there were lot things that may explain why I had some “freak” results. Some of the things that I may have affected my results are-

• When I was doing the re-tests, I got more insulation layers the same size as at the beginning, and the wrapped them round the beaker. This time they were loose around the beaker. This would have affected how close the insulation layers were together and therefore affected my results.
• When we were timing the heat loss on one beaker, we would have been re-boiling the kettle close by. This would have made the air around it warmer therefore it might have heater up the beaker, which would affect our results.
• When we were pouring the water into the beaker a lot of steam/heat was lost before we put the lid on.
• Once we had put the lid on the beaker, the lid got wet through condensation and evaporation. This then meant that next time we did an experiment the lid had changed in shape.
• We attached the insulation onto the beaker using cello tape, this seemed alright for the first few experiments, but when it came to taking the insulation off, it had melted, therefore making the next piece off insulation come off with it, so we had to re-stick it back on.

I could have improved my experiment if I had done –

• If I had done all of my experiments with the same amount of layers of insulation at the same time, after each other.
• Boil the kettle away from the experiment.
• Put a layer of insulation under the lid and swap it after each experiment to prevent the lid from getting wet.
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I could have made my experiment better and more conclusive if I had had a larger range, maybe go up to 10 layers; because some of my results seemed to make sense but there were some that didn’t fit the pattern. If I had had a larger range I would have been able to get more evidence that would enable me to support my conclusion. Also if I had had time I would have re-done some more results as I have quite a few odd results and then I could have compare these to my results to see which ones were accurate and which ones weren’t.

The odd results I got were probably due to the errors I made and bad accuracy.

Conclusion

The pattern was that the more insulation layers the smaller the heat reduction. This is what I put I put in my prediction. Although this didn’t happen in all of my results it happened in some.