Biology: Osmosis and Diffusion Lab using Potato Cores Class: 3B Mr. Boyer Name: Simon Han Abstract: In this experiment, we learnt about Osmosis and Diffusion through potato cores in different concentration of sucrose, (water, .2, .4, .6, .8, 1.0). We realized that the lower the concentration, the higher the potato cores weighed. However, our result was quite off for the potato cores in .8 sucrose concentrations. The graph should decrease, but our graph was decreasing and suddenly crosses the x-­‐axis then down again. Our graph had 3 x-­‐intercepts. The equation of our graph is y = -­‐46.56x + 34.76. Our x-­‐intercept of the best-­‐fit line is (1.34, 0). Although our graph and our results were off, it still partially backed up our hypothesis. Research Questions: How does Osmosis affect the weights of object in different concentrations? Introduction: All cells have membranes that are selectively permeable. In other words, they allow certain things in and certain substances are not allowed to enter the interior of the cell. The process by which water crosses membranes from regions of high water concentration to regions of low water concentration is called Osmosis. Osmosis is the process whereby water moves across a cell membrane by diffusion. Diffusion takes place when the molecules of a substance tend to move from areas of higher concentration to areas of lower concentration. Cells must tightly control the process of osmosis otherwise they will die. Plants with too little water will wilt. This happens when water moves out of the cells by osmosis. Without this water there is little pressure inside the cells and the plant can no longer support itself against the pull of gravity. Hypothesis: The more hypertonic potato cores are to sucrose solution, the more weight potato cores gain. On the other hand, potato cores will decrease in weight when it is hypotonic to sucrose solution. Variables:  Dependent: The final mass of the potato cores  Independent: Concentration of sucrose  Controlled: Size of potato, time spent in solution, amount of solution Apparatus: •
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Potato cores (4 per condition) Sucrose solutions (.2, .4, .6, .8, 1.0) Distilled water Electronic balance Plastic weighing tray Plastic cups (6) Graduated cylinder (50 ml) Scalpel Marking tape Blue tweezers Procedures: 1. Using marking tape, label 6 cups with the following solution types (.2, .4, .6, .8, 1.0 and Di water). 2. Place approximately 50 ml of the various solutions, each cup receiving a separate solution. Suggestion, measure the di water with the graduated cylinder, and fill the other cups to the same level 3. Obtain 24 potato cores and cut them to equal sizes (about 2.5 cm). All the cores you use must be the same length 4. Divide your 24 cores into 6 groups and gently blot them dry with a paper towel 5. Using the electronic balance and plastic weighing tray mass (weigh) each group of potato cores and record the data in a table that is labeled with a detailed title and which provides the error measurement of the electronic scale. MAKE SURE TO TARE THE TRAY. The table should record the type of solution in the cup and the mass of the potatoes in the cup. 6. Place the potato core sets in their appropriate cup and place in Mr. Boyer’s back prep room in the fume hood that is labeled with your block (3B or 4B). 7. 24 hours later (app) you will need to come and measure the mass of your potato cores. To do this you must pore off the fluid in the cup and use the plastic blue tweezers remove the cores, blot them dry just as you did in the set up phase and final measure them using a plastic weighing tray. MAKE SURE TO TARE THE TRAY. Record your potato group mass on your data chart. 8. Finally dump your potato cores in the trash and wash and dry your equipment (cups, tweezers and return them to their stations. 9. Calculations. For each setup (all 6) you will need to calculate a percent mass change. To do this you will use the following formula (final mass-­‐initial mass)/initial mass x 100. You will need to record this data in your data table as well. Make sure to keep track of the positive and negative changes if they occur. same
Figure 2 This is a picture of potato
Figure 1 This is a picture of potato
cores
cores cut in same sizes
before
getting
cut
in
sizes.
Figure
4
This
potato core.
pictures
shows
one
Figure
3
This
potato cores.
shows
6groups
of
4
electronic balance zeroed out with
the tray on it. This was before we
measured each groups of potato
cores.
Figure 8 This is another set of potato
cores
on
the
electronic balance.
Figure
5
This
is
a
picture
of
the
Figure 6 This is a picture of a group
of
potato
cores
on
the
electronic
balance.
Figure 7 This is the organized data
with
errors
potato cores.
for
each
groups
of
the Figure 10 This is a picture of the
Figure
cup
independent variables, which is the
labeled
with
water
and
graduated cylinder.
9
This
is
a
picture
of
our
concentration of the sucrose.
Figure 11 This is a picture of the
potato
cores
concentration
after
of
24
hours
sucrose
in
on
.2
the
electronic balance.
Figure 14 This is a picture of the
potato
cores
concentration
after
of
electronic balance.
24
hours
sucrose
on
in
.6
the
Figure 12 This is a picture of the
potato
cores
concentration
after
of
24
hours
sucrose
in
on
.4
the
electronic balance.
Figure 13 This is a picture of the
potato
cores
concentration
after
of
electronic balance.
24
hours
sucrose
on
in
.8
the
Figure 16 This is a picture of the
potato cores after 24 hours in 1.0
concentration of sucrose on the
electronic balance.
Figure 15 This is a picture of the
potato cores after 24 hours in water
on the electronic balance.
Data Chart: Concentration 0 .2 .4 .6 .8 1.0 Percentage Change 39.13 % 25 % 13.04 % -­‐4.35 % 9.09 % -­‐13.04 % Table 1 This table shows our final results.
Graph 1 This graph shows our final result. It is not the
best result we have expected. Something went wrong during
our lab.
Graph 2 This is the graph of the group's result. As shown, our X intercept is way off of others. We are group 1. Conclusion: Analysis of results and graph: Analysis Result The results were quite ambiguous and vague. It was hard to conclude that the more hypertonic potato cores are to sucrose solution, the more weight potato cores gain. Our X intercept was quite off compared to other groups. However, we noticed that the numbers were decreasing while the concentration was higher, except for the one in the concentration 0.8. Other groups’ points were around 0.2 to 0.4. However, our point was 0.75, which was way off of other groups’ points. Graph Except for the point of potato cores in 0.8 concentration of sucrose, which gave us a positive number, the graph shaped similarly with other groups’ graph. Our group’s graph is decreasing, except for the point of 0.8, which seems like a mistake, just like what we had stated on the hypothesis. Also as shown above, the graph shows significant difference between our group’s x-­‐intercept with other groups’. Evaluation: My Lab (method): Generally the method seems to work well to get suitable results but part of it could be improved to get even better results. Limitation Improvement The length of the potatoes might not Try 3~4 times to get as accurate be all the same. results as possible. Not enough experiments with different Conduct the experiment adapting 6 independent variables. different independent variables. Experiment under independent variable conducted one times. the was same Repeat the same experiment 3~4 only times. The amount of each concentration Check the graduated cylinder more might not be exact and same. than once to get as exact as possible. The electronic mass kept on changing Wait 1 minute then record what we from 2.2-­‐2.4 g see. Reliability: Generally the method seems to work well to get suitable results but parts of it were not reliable. We made an effort to make the experiment as accurate as possible. However, once again, shown in the graph, there was a mistake in either measuring or reading. If we were to have more time and would conducted more experiments, we could have gotten better, more exact results. Result: The result was also generally satisfying because it supported parts of my hypothesis. However some results were a little vague to conclude. As seen in the graph above, the results did not follow a significant pattern. However we could conclude that the graph was decreasing just like other groups’ works. Our result somehow supports our hypothesis, which is the more hypertonic potato cores are to sucrose solution, the more weight potato cores gain. On the other hand, potato cores will decrease in weight when it is hypotonic to sucrose solution. Suggestion: For better quality of the experiment and for more exact, accurate results, we should have done the experience 3~4 times and get the average and delete the more extreme results, like what we got for the potato cores in 0.8 sucrose.