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To investigate the effect of changing the P.H. level during the fermentation of yeast; and to see how much the yeast ferments at the different P.H ’s.

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Introduction

James Mckenzie 10L Biology Course-work Planning Experimental Procedures Aim To investigate the effect of changing the P.H. level during the fermentation of yeast; and to see how much the yeast ferments at the different P.H 's. Prediction When the P.H. level is at a neutral point the amount of fermentation will be consistently higher, than if not. Therefore when the P.H. level is at a low or high number i.e. acid or alkali, the amount of fermentation will be considerably less than if it is at neutral P.H. The stronger the alkalinity or acidity will give even less fermentation than a weak acid or alkali. ...read more.

Middle

* Dissolve 8g of sugar in 125cm� of warm water (40 centigrade) * Add 15g of yeast and stir well * Leave for 7 minutes for the yeast to become active The experiment was set-up as shown on the separate sheet of paper. 1st experiment * P.H. 3 during fermentation. * 7 minutes left fermenting * 5ml CO2 gas 2nd experiment * P.H. 6 * 7 minutes fermenting * 15ml CO2 gas Decisions about Experiment The preliminary experiment showed the outline of the prediction we made. The first experiment whereby the P.H. was 3 showed that a low P.H. i.e. a strong acid does not produce a huge amount of acids. ...read more.

Conclusion

In the preliminary as soon as the method was set-up properly. This did not allow a long enough time for the fermentation to take proper affect. This was because the glass tube linking the boiling tube and the measuring cylinder was full of water. This water has to be pushed back down the glass tube, this slows down the fermentation, and does not allow a vast amount of gas to be collected. To stop this from happening we must start the stopwatch when the gas has actually reached the measuring cylinder. The time allowed for the gas to be collected is too short; it does not give sufficient amount of gas in order to see how the P.H. effects the fermentation. Therefore the time for each experiment is extended to 10 minutes to allow sufficient gas to be collected. ...read more.

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