Osmosis and Diffusion Lab Using Potato Cores Lab

Osmosis and Diffusion Lab using Potato Cores Instructions and Rubric Cindy Shin Biology 4B

Research Question •

Will there be any differences in the movement of water in or out of a set of potato cores depending on the different concentrations of sucrose?

Introduction •

In this lab, we put a set of potato into six cups with different amount of sugar mixed with water. The purpose of this lab was to see how the materials move in and out of the potato according to the difference in concentration; materials always move from high concentration area to low concentration area. As water couldn’t move in and out by itself, the transport that was used in this process is called facilitated transport: Facilitated transport is where the protein channel helps the movement of materials through the membrane, because they can’t get through by themselves. In conclusion, we observed how the water moves in and out of the potato according to the concentration on either side of the membrane.

Hypothesis •

If the concentration of the sugar in the water is larger, then the set of potato in the cups is going to get bigger.

Variable Identified • • •

Independent Variable: The concentrations of sucrose in each cup Dependent Variable: The size of the set of potato Controlled Variable: The potatoes that are being used and the time spent after putting the potatoes in the cups

Materials • • • • • • • • • • •

You will be working in groups of 4 if at all possible to share the work load (2 buddy groups) 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 • •

Using marking tape, label 6 cups with the following solution types (.2, .4, .6, .8, 1.0 and Di water) 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 • Obtain 24 potato cores and cut them to equal sizes (about 2.5 cm). All the cores you use must be the same length • Divide your 24 cores into 6 groups and gently blot them dry with a paper towel • 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.

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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).

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PS make sure to indicate on your cup your group number, Mr. Boyer will assign group numbers during the lab 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. Finally dump your potato cores in the trash and wash and dry your equipment (cups, tweezers and return them to their stations

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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

Data Chart Initial Mass Final Mass Formula Water Sucrose 0.2 Sucrose 0.4 Sucrose 0.6 Sucrose 0.8 Sucrose 1.0 • • •

2.4g 2.4g 2.4g 2.4g 2.4g 2.4g

2.6g 2.7g 2.3g 1.9g 1.8g 1.4g

Mass Change

(2.6-2.4)/2.4 * 100 (2.7-2.4)/2.4 * 100 (2.3-2.4)/2.4 * 100 (1.9-2.4)/2.4 * 100 (1.8-2.4)/2.4 * 100 (1.4-2.4)/2.4 * 100

8.3% 12.5% -4.2% -20.8% -25% -41.7%

Formula: Final mass – initial mass/initial mass) * 100 = % mass change Error measurement for all the masses measured is 0.05g. Error measurement for all the percent calculation is 0.05%.

Graph of the Results

% Mass change vs. concentration  20 

% Mass change 

10  0  0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

‐10  ‐20  ‐30  ‐40  ‐50 

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Concentration 

This is the graph that shows percents of mass change in potatoes verses the sucrose concentration. The slope is negative, which shows that the percent of the mass change decreases while the sucrose concentration increases. The line drawn on the graph is the best-fit line, which shows the approximate slope of the data; the x-intercept of the best-fit line represents the water potential of the potato cores.

Conclusions • Looking at the results that I have observed, I can see that the mass of the

potatoes increased while the concentration of the sucrose decreased. This shows that the higher the concentration of the sucrose is in the water, the more water is released from the potatoes. The fact that the water has more sucrose in them tells us that there is less water in the cup; as there is not enough water in the cup, the water from potatoes has to come out to make the concentration the same across the membrane. Materials move from higher concentrated area to lower concentrated area. Since the sucrose concentrations increased, the potatoes released more water from themselves. The best-fit line in the graph touches the x-axis at 0.28. This point indicates the water potential of the potato cores.

Sugar Concentration vs. Percent of Mass  Change  80%  60% 

Percent of Mass Change 

40%  20%  % of Mass Change G4 

0%  ‐20% 

SC 0 

SC 0.2 

SC 0.4 

SC 0.6 

SC 0.8 

SC 1 

% of Mass Change G3  % of Mass Change G2  % of Mass Change G1 

‐40%  ‐60%  ‐80%  ‐100% 

Sugar Concentration 

This graph is the data of mass change according to the sucrose concentrations from each four group. The graph shows that all the x-intercept from four groups is about 0.26 to 0.29. The difference of the solute concentrations inside the cores might have occurred of several reasons. One of the reasons is that some of the groups might not have measured the mass of the potatoes correctly after taking them out of the sucrose water; they might not have dried the potatoes completely before putting them on the weigh. In conclusion, the graph shows that the water potential of the potato cores is fairly the same for all the groups: about 0.26 to 0.29.

Evaluation/Reflection •

This lab was pretty easy to accomplish, because all we had to do was to put the set of potato in six cups of different sucrose concentration and to wait for a day, and collect data from that. In the beginning of the lab, cutting the potatoes into the same sizes was a success to our group, because we ended up with having the same mass for all the potatoes. During the lab, we didn’t have that many difficulties. However, one difficulty that occur during the lab was that collecting data the next day. After taking the potatoes out of the six cups, we had to dry them before weighing their mass; this process was challenging because the data wouldn’t be as accurate if the potatoes are perfectly dried. So below the chart that I made, I wrote the error measurements for the masses that have been weighed. Through this lab, I learned that the materials move from higher concentrated area to lower concentrated area. Before I did this lab, I was confused how the concentration affects the movements of the materials, and also, how the materials get into or out of the membrane. After accomplishing the lab, those concepts became clear and were easier to understand than before. If I have an opportunity to do this lab again in the future, I would like to enhance my work by collecting data as accurate as possible, so that there wouldn’t be any differences compare to the other groups. During this lab, not all the group members had chance to look at the results of the mass change in potatoes, because only a few people went to check the potatoes during lunch time. So if I could, I would like to observe the results more carefully with more accurate data.