This lab report describes experiments measuring yeast growth by varying the amount of sugar. The hypothesis was that increasing the amount of sugar would increase the amount of carbon dioxide produced. Three trials were conducted using 5g, 10g, and 15g of sugar. The data showed inconsistent results, with no clear relationship between sugar amount and gas production. On average, the lowest sugar amount of 5g produced the most gas. The conclusion is that the hypothesis was not supported, and the data was untrustworthy likely due to errors in measuring and mixing the sugar and yeast amounts between trials.

1. Name:…………Bonghee Han…………………..
Yeast Experiment

3.
Science Lab Report
Yeast Growth
Experiments date­20~22/OCT/2010
Group member­ Bonghee, Jaffer, Toby Bonghee Han
Aim
The purpose of yeast growth experiment is to know basic knowledge of cell
respiration by changing some variable.
Hypothesis
Before starting experiments prediction was by changing amount of sugar the
carbon dioxide will increase or decrease in direct proportionally. When the
amount of sugar is increase the carbon dioxide also increase. When amount of
sugar decrease carbon dioxide is decrease.
Variable
Input variable
Amount of sugar: 5g, 10g, 15g of sugar
Sugar will be measured by electric weight without napkin.
Output variable
Gas collection: How much ml of gas collection is moved
Stop watch: Measure time for 10mins and for each min record
Control variable

4. #1 100ml of water for each experiment
At the beaker there is the line to give information
#2 Same size of beaker which is 200ml
At the experiment beaker will be same
#3 Same amount of yeast that is 5g
Use electric weight to measure
#4 Same size of gas collection which is 100ml
Same types of gas collection
#5 Same degree of water temperature
There is machine to keep the water temperature same
Equipment
• 45g of yeast
• 90g of sugar
• One 200ml flask
• One 100ml of gas collection
• 300ml of water
• One cork
• One electric weight
• Water bath
Diagram
Method

5. 1. Set up the equipment as shown as Diagram
2. Ready 5g of yeast for each experiment
3. Ready 5g of sugar for each experiment
4. Put 100ml of water into 200ml of flask
5. Put sugar and yeast
6. Start stop watch
7. Take note for each min until 10mins
8. Clean the 200ml of flask
9. Repeat steps 2 to 8 using masses of 10g, 15g
10. Clean all the equipments
Data
Table 1: Amount of sugar verses the amount of CO2 produced
5g of sugar 10g of sugar 15g of sugar
ml B‐Beginning
B F B F B F F‐Final
Trial
Trial 1 5 76 3 18.5 0.5 24.5
Trial 2 2 17 3 29 3.5 27
Trial 3 3 27.5 2 75 1 63
Table 2: Amount of sugar verses the amount of CO2 produced
<Average>
Trial ml 5g 10g 15g
Trial 1 71 15.5 24
Trial 2 15 26 23.5
Trial 3 24.5 73 62
Average 36.8 38.2 36.5
Graph

6. 80
Yeast growth
70 5g
60 10g
15g
50
Gas(ml)
40
30
20
10
0
Trial 1 Trial 2 Trial 3 Averge
Trial
Conclusion
According to the experiments data. There is no pattern for the data table 1
because for first trial 5g was the most improvement and for second trial 10g
were the most improvement and the third trial 15g was the best. But when it
turns to average there is pattern. If the human body consumes less sugar it
produce high CO2. When human body consumes as many as body did it produce
less CO2. The hypothesis was not reliable because it was when sugar increase
body produces more CO2. The data is untrustworthy because it was all different
result from same experiments.
Evaluation
The method is trustworthy because it was the just listed basic ways. And
there is repeating the process. Also method was ok but problem was the a bit
different weight of sugar and the yeast. The three trials is completely error after
experiment water for clean was not dried so yeast and sugar stick to top of
flask. The error had huge effect to the experiment mixture of sugar and yeast
were not completely mixed. The method should have more pacific of variable to
do not change the result in same method of experiments.