As a culture of yeast is merged with solution of sugar, a reaction called fermentation occurs. As products, ethanol and carbon dioxide are produced, in form of liquid and gas respectively.

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Planning

        As a culture of yeast is merged with solution of sugar, a reaction called fermentation occurs. As products, ethanol and carbon dioxide are produced, in form of liquid and gas respectively. The reaction follows this equation:

Glucose solution + Yeast Carbon dioxide + Ethanol + (Energy)

        And as one of the products is in the form of gas, the volume of the product can be measured to demonstrate the difference of the reaction when certain factors are changed. In the other words, the rate of reaction can be illustrated by doing appropriate calculation involving the volume of gas produced.

        Key factors that can affect the rate of fermentation are:

* Concentration of sugar solution;

* Type of sugar;

* Temperature of the environment;

* Age of the yeast culture and size of the yeast culture:

*pH of concentration.

The factor chosen is the concentration of sugar solution, so the others factors are to be kept constant as control factors in order to make this investigation fair. Here are the control conditions:

* Sugar used is glucose, because it is a mono saccharine, easy to decompose;

* Temperature of the environment is 30??C, so that there is enough energy and the enzymes do not denature;

* The yeast is to come from the same source, so they are at the same age.

However, the size of the yeast culture is the factor that cannot be controlled because the yeast samples divided from the initial culture have to be bred in different sugar concentration, which provides different conditions, varying the suitability of reproduction. The next question is how long shall the results be taken for. The initial guideline should be 30 minutes, enough for significant production, with 5 minutes interval for each measurement. However if the rate is too fast and if the meniscus should reach the point where no further reading could be taken, it should end there. The volume of the yeast mixture should also be used in the same quantity throughout the investigation. The considerate quantity is about 2cm3, considering the size of the test tubes themselves. The mixture should be gently shaken to blend the solution and the culture together, as the culture tends to settle at the bottom over a certain time. To make this a fair test, the experiment is to be repeated twice, giving 3 results for each in total, then the average is used and analyzed finally. To save time, several tubes could be set up at the same time, and the measurements could be taking simultaneously. Preferably all the experiments of the same set should be started at the same time, as different age of the culture would matter how quickly fermentation occurs.

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The most important question is what sugar concentrations should be used, and the concentration chosen are 50%, 100%, 150% and 200%. The 100% solution is made of 3g of sugar, mixed with 100ml of water; 150% is made of 4.5g; 200% of 6g; and 50% of 1.5g respectively.

Prediction

        Theoretically, the higher the concentration is, the faster fermentation should happen. However, if osmotic pressure module is to be taken into account, this theory may not work. If the water potential of the environment is low, the cells are going to lose water through osmosis. This would make fermentation less ...

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