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The effect of temperature on the production rate of carbon dioxide in yeast.

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Introduction

BIOLOGY COURSEWORK The effect of temperature on the production rate of carbon dioxide in yeast. Introduction: We are using yeast balls to work out what affects the production of carbon dioxide. The reaction to be studied is as follows: C6H12O6 C2H5OH + 2CO2 (+ 2 ATP) There are four factors which affect the reaction rates : surface area, use of catalyst, concentration and temperature. It is impossible to vary the surface area , as if the yeast balls were chopped up into small pieces, then the yeast inside would die, and so no reaction would occur. The use of catalysts is a hit-and-miss variable, as it is basically putting in random chemicals and seeing if they react. Both temperature and concentration are suitable for variation, but I have decided to change the temperature, as I do not think that varying concentration (i.e. amount of yeast balls), would be that effective. ...read more.

Middle

Increased temperature means an increase in kinetic energy of the molecule, hence a greater reactivity. Hypotheses: The higher the temperature of the reaction, the faster the reaction rate. I believe that this will be true until about 70 oC, at which point the yeast cells shall start to denature. This means that it will affect the upper values. Key: - HCl molecule - yeast cell There is the same amount of acid and yeast in both container (i) and (ii), but container (ii) has a higher reacting temperature. Therefore, it speeds up the random motion of molecules and the yeast cells will have much more energy and therefore, collide quicker and with more force. This means that the reaction will occur much quicker. As the temperature increases, the time taken for 1cm3 of CO2 to be produced decreases, meaning the reaction rate is faster. And as the values for the reaction rate are directly proportional to 1/t (or indirectly proportional to t), I have drawn up the above hypotheses graphs. ...read more.

Conclusion

So, I have therefore decided to see how long it takes to make x cm3 carbon dioxide. Now I have to decide how much CO2 am I looking to collect for the experiment. Having said that at low temperatures, the reaction rate is very slow, I have decided to see how long it takes for 1cm3 to be collected. Also, to ensure that the experiment was correct, I set up another one, where instead of collecting the CO2, I bubbled it through HCIS solution, to ensure that it was in fact carbon dioxide. This proved positive. The results are as follows: Temp (oC) 40 50 60 70 80 90 Time to collect 1cm3 (s) 1733 1652 1138 1100 1078 784 These results are not as I predicted, and so I can see that I have either made an error, or my hypothesis was wrong. However, after talking to the rest of the class, I have decided that the yeast must have been a bad batch, because nobody really got good results. ...read more.

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