osmosis and diffusion lab using potato cores...

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:

• 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.

Figure 2 This is a picture of potato

cores before getting cut in same

sizes.

Figure 1 This is a picture of potato

cores cut in same sizes

Figure 4 This pictures shows one

potato core.

Figure 3 This shows 6groups of 4

potato cores.

Figure 5 This is a picture of the

electronic balance zeroed out with

the tray on it. This was before we

measured each groups of potato

cores.

Figure 6 This is a picture of a group

of potato cores on the electronic

balance.

Figure 8 This is another set of

potato cores on the electronic

balance.

Figure 7 This is the organized data

with errors for each groups of

potato cores.


cup labeled with water and the

graduated cylinder.

Figure 9 This is a picture of our

independent variables, which is the

concentration of the sucrose.


potato cores after 24 hours in .2

concentration of sucrose on the

electronic balance.




electronic balance.




electronic balance.




electronic balance.


potato cores after 24 hours in 1.0


electronic balance.


potato cores after 24 hours in water

on the electronic balance.

Data Chart:

Concentration Percentage Change

0 39.13 %

.2 25 %

.4 13.04 %

.6 -‐4.35 %

.8 9.09 %

1.0 -‐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

be all the same.

Try 3~4 times to get as accurate

results as possible.

Not enough experiments with different

independent variables.

Conduct the experiment adapting 6

different independent variables.

Experiment under the same

independent variable was only

conducted one times.

Repeat the same experiment 3~4

times.

The amount of each concentration

might not be exact and same.

Check the graduated cylinder more

than once to get as exact as possible.

The electronic mass kept on changing

from 2.2-‐2.4 g

Wait 1 minute then record what we

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.

osmosis and diffusion lab using potato cores...

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