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In this experiment, I am going to investigate the effect of heat on the respiration of yeast.

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Introduction

Biology Coursework Planning Title In this experiment, I am going to investigate the effect of heat on the respiration of yeast. Safety When doing the experiment there will only be one main hazard and that will be the hot water. One way of controlling this hazard is for the teacher to bring us the hot water instead of all walking to the front of the classroom to get the hot water. To always have green paper towel so that if the beaker needs picking up the green paper towel can be wrapped around the beaker and used as a handle and instead of pouring the hot water from the beaker into the other beaker, use a dropper to transfer the water. Another way of controlling the hazard of hot water is to keep all electrical sockets and electrical equipment off when someone is not keeping an eye on them; this is because water near electricity can cause someone to have an electric shock. It is also important to make sure that if any water is spilt on the floor it is wiped up immediately so as not to cause someone to slip and hurt themselves. These points would all help in preventing a hazard. Prediction I think that as the temperature rises by 10�C each time the rate of Carbon Dioxide bubbles produced will double. I think that his will happen until the temperature of the water reaches 40�C, when I think that the rate of carbon dioxide bubbles produced will fall quite dramatically. Scientific Explanation I think that every time the temperature goes up by 10�C the rate of Carbon Dioxide bubbles produced will double because the higher the temperature of the water, the more energy the molecules involved in the reaction has. This makes them move around faster, increasing the chance of them colliding with one another, with enough energy to cause a reaction. ...read more.

Middle

When I collect all the results for 30�C I will do the same experiment with the same process for 20�C, 10�C, 40�C and finally 50�C remembering not to change the water or the yeast solution but only the temperature of the water. I will also remember to keep the level of the water at 200ml so that it is a fair test. I will have to take great care when counting the bubbles and not take my eye of the test tube while counting in order not to miscount, however if I do or I find anomalous results I will carry on counting for a few more minutes and collect results for four and five minutes. I will then take the three values that are closest out of the five and I will take an average of the three to get how many bubbles on average were made for each temperature. I will then plot these results on a graph. Obtaining evidence These are a set of my first results: Number of Bubbles per minute/mins Temperature/�C 1st Minute 2nd Minute 3rd Minute 10�C 3 2 2 20�C 9 10 11 30�C 20 21 24 40�C 43 49 49 50�C 26 23 25 After repeating the experiment and drawing a graph, I made no changes because I found nothing wrong with the experiment I chose to do before, and nothing showed up on my graph that would make me need to change anything. The only thing was that I sometimes missed a bubble or two so I have to concentrate harder on what I am doing when I do the experiment. The numbers that are in bold are slightly anomalous as they are not around the same range as the other numbers at that particular temperature. As I have said above the only way that I will be able to make sure that I do not get any anomalous results is to be more careful when counting the bubbles and try to be as accurate as possible with the control variables and the independent variable. ...read more.

Conclusion

I do not think that my results were at all random areas but instead I think they were systematic errors, which meant that there was a constant fault in the equipment that I used the materials or the technique. "Safety of Conclusion" I do not think that my results were sufficiently accurate to draw an excellent conclusion but I think that they are good enough to prove some of the points that we are trying to make. I do not think that my results were bad compared to anyone else's; I think that they were around the same. Repetition did improve the accuracy of my results a lot and I am sure that if enough time was given and I repeated the results over and over again I would get almost perfect accuracy. Further Work As my further work, I predicted what would happen beyond 50�C. I worked out that it should just drop off but I have yet to prove this. I do not think it would be possible to do the experiment much lower than 10�C, because although enzymes do not denature at cold temperatures, they stop working so therefore if you were meant to draw the graph using lower results then 10�C and higher than 50�C, the graph would look like this. As well as looking at what would happen if I extended the range, I also looked at another method that could be used to do the experiment that would be more reliable. I thought that the downward displacement method would have been more reliable because it would have been possible to measure the actual volume of gas instead of having to count the bubbles. This would have been more accurate as when counting the bubbles it was possible to miss a few or miscount but when using this method it was pretty hard to miscalculate as all that would have to be done would be to read the reading on the side of the measuring cylinder which is a lot easier than counting bubbles. Alisha Meertins 10PB Mr Beckley 1 ...read more.

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