Hypothesis:
If the temperature in which the yeast is placed in is increased than the number of yeast reproduced is also increased.
Materials:
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6 Petri Dishes ● Paper Towel
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1 Digital Scale ● 1 Pencil
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1 Pipette ● 54 ml of Water
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Six 650 ml beaker ● 6 pieces of paper
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6g of Sugar ● 1 Incubator
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180 pieces of Yeast ● 1 Fridge
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1 Scapula ● 1 stirring rod
Procedure:
1. Gather all the materials needed.
2 Using a scapula 30 pieces of yeast were transferred into each of the six Petri dishes.
3. The six Petri dishes that each contained 30 pieces of yeast were labeled according to the temperature and as sample 1 or 2.
4. Using a pipette 9 ml of water was transferred to each of the six 50 ml beakers.
5. Using a digital scale 1g of sugar was weighed and rested on a piece of paper.
6. The sugar on the piece of paper was transferred to 50 ml beaker containing 9 ml water.
7. A stirring rod was used to dissolve the sugar into the water.
8. The sugar water solution in the beaker was transferred into the Petri dishes and sealed.
9. The low temperature Petri dishes were placed into a fridge overnight.
10. The room temperature Petri dishes were placed onto a shelf in the classroom overnight.
11. The high temperature Petri dishes were placed into an incubator overnight.
Results:
Table 1: Amount of Yeast Produced Overnight at Different Temperatures
Discussion:
At low temperatures (0-10 C) yeast will not grow, but not die either. At temperatures 10-37 C yeast will grow and multiply, faster at higher temperatures with an optimal growth at 30 or 37 C (that depends on the species). At higher temperature the cells become stressed, meaning that their content becomes damaged and which can be repaired to some degree. At high temperatures (>50 C) the cells die. The bacteria can survive freezing under certain conditions. The yeast had varied results for each of the different temperatures. The low temperature (0-10 C) had the least amount of yeast produced overnight whereas the high temperature (>50 C) produced a high amount of yeast. The yeast fermentated differently according to the temperature that it was in, which means there is an ideal temperature that yeast can most effectively grow in. From the results, it can be concluded that at higher temperatures the yeast are able to fermentate at a much higher rate than that of the other two temperature levels.
Experimental Errors:
Though every Petri dish and beaker was weighed on the scale before every trial, and accurate sample weights were taken from the yeast and water, there is still the possibility that when transferring the experimental materials from the beakers and Petri dishes in which the reaction occurred, their could have been left over materials that did not take part in the reaction, therefore resulting in a lower weight of reactants then what was measured for the beginning of the experiment. While dissolving the sugar in the water a few drops were lost due to rigorous shaking. One or two extra pieces of yeast may have fallen into Petri dishes while they were being counted which increased the number of our constant. Counting pieces of yeast proved to be difficult using microscope which may have caused our yeast count to be inaccurate. Grains of sugar fell off the pieces of the paper and onto floor which affected the weight of the sugar by a small amount.
Conclusion:
As the temperature at which the yeast was placed in increased, the number of yeast reproduced also increased. The number of yeast in the cold temperature changed a little while at the same time the number of yeast in the warm temperature increased greatly. The volume change indicates that the yeast in the high temperature were more active than the yeast in the cold temperature. The yeast reproduced in the room temperature was greater than that of the high temperature but lower than that of low temperature. . Experimental errors such as transferring the experimental materials from the beakers to the Petri dishes in which contained the yeast, there could have been left over materials such as sugars that were not consumed by the yeast. Also, other minor experimental errors such as not washing the containers properly and grains of sugar that could have fell off the pieces of the paper and onto floor which affected the weight of the sugar by a small amount may have contributed to different results.
