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Experiment testing the Time taken for Yeast to rise in Glucose at different Temperatures.

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Experiment testing the Time taken for Yeast to rise in Glucose at different Temperatures Planning Aim: To see how temperature affects the rate of respiration. Investigation plan: * Prepare 5 test tubes. * Add 8 yeast balls to each test tube. (A yeast ball contains little yeast cells. When glucose is added to these at the right temperature, the enzymes cause the fermentation reaction to take place (C6 H12 O6 CH3 CH2 OH + CO2. The yeast becomes less dense causing it to rise.) * Prepare 5 water baths of temperatures 20�c, 30�c, 40�c, 50�c and 60�c. Kept constant by adding hot and cold water depending on the temperature being checked using a thermometer. * Place the test tubes in each different water bath and add 25cm� of 10% glucose to the test tubes. * Time how long it took for the first yeast ball to rise in each of the test tubes. * Note down the results. * Keep a fair test by keeping the amount of glucose and the concentration of glucose the same throughout the experiment. * The results will be reliable because we will repeat the experiment twice and get an average for each temperature. ...read more.


The temperatures we are using are between 20�c and 60�c. Scientific Knowledge: If the temperature is too low there will not be enough energy for a reaction to take place because of the collision theory. If the temperature is too high the enzymes will denature and the reaction will not occur. To work properly the temperature needs to be close to the optimum temperature of the enzyme. This is usually body temperature that is 37�c. Method (with changes): After doing preliminary work we decided to do the experiment slightly differently to the way we first planned. We prepared 5 test tubes with 4 yeast balls in each. We decided to change the amount of yeast balls because on our first try of using 8 yeast balls nothing happened even at 40�c. We added the 5 test tubes to water baths of temperatures 20�c, 30�c, 40�c, 50�c and 60�c. We then times how long it took for one yeast ball to rise and noted the time down. We then repeated the experiment for each different temperature so we could get a more reliable average. Results Table showing results including averages and rate. Temperature Time A Time B Average Rate = 1/time (seconds) ...read more.


It shows that the rate peaked at 50�c and then started to drop at 60�c. 20�c was not included on the graph because no reaction took place at this temperature. Evaluation The experiments results differed from what I had predicted. From my results there were no anomalies so my results should have been very accurate. They are accurate because the results for each of the different temperatures are similar and it is unlikely that it went wrong all 3 times. This means that my prediction was wrong. I predicted that the enzyme would work best at body temperature, which is between 30�c and 40�c but my experiment proved that the enzyme works best at close to 50�c. The optimum temperature for fermentation is about 50�c. If I were to do this experiment again I would maybe use a higher concentration of glucose because this would mean that the reactions would happen faster and there would be a faster rate. Doing this would mean that I would be able to repeat the experiment for the same time a couple more times and I would therefore be able to get a more accurate average. If I were to do the experiment again I would also time how long it takes for all of the yeast balls to rise because this would mean a larger difference in rates/times between the different temperatures. By 1,312 words ...read more.

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