Potato Osmosis Lab PDF

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Potato Osmosis Lab...

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Demonstrating the Osmolarity in Potatoes and Sucrose Table 1: Data Showing the Relationship Between the Change in Mass (grams) of Potatoes and Varying Concentrations of Sucrose (moles) Concentration of Sucrose Solution

Trials

Initial Mass (grams)

Final Mass (grams)

Change in mass (%)

1

0.80

0.78

-2.5

2

0.81

0.82

1.2

3

1.8

1.97

9.44

4

1.03

1.27

23.30

5

1.1

1.38

24.3

1

0.82

0.88

7.3

2

0.87

0.88

1.1

3

1.7

1.92

12.94

4

1.12

1.19

6.25

5

1.08

1.14

1

1

0.67

0.72

7.46

2

0.69

0.65

-5.797

3

1.72

1.84

6.97

4

1.07

1.09

1.86

5

1.17

1.21

3.41

1

0.76

0.58

-23.68

2

0.82

0.64

-28.125

3

1.65

1.25

-24.24

4

0.96

0.79

-17.71

5

1.13

0.81

-28.3

(moles)

Distilled water (0M)

0.1M (sucrose)

0.2M (sucrose)

0.5M (sucrose)

1M (sucrose)

2M (sucrose)

1

0.75

0.63

-16

2

0.72

0.69

-4.16

3

1.54

0.93

-39.61

4

0.97

0.64

-34.02

5

1.05

0.83

-20.9

1

0.71

0.52

-26.76

2

0.72

0.50

-30.55

3

1.61

0.81

-49.69

4

0.94

0.81

-13.82

5

1.14

0.7

-38.5

Processing of Data: Change in Mass f inal−initial initial

× 100

Table 2: Average Change in Mass (%) For Each Varied Concentration of Sucrose (Moles) Average Change in Mass of Potatoes (%) Distilled water

11.148

0.1M Sucrose

5.718

0.2M Sucrose

2.781

0.5M Sucrose

-24.411

1M Sucrose

-22.938

2M Sucrose

-31.864

Figure 1: Graph Showing the Average Change in Mass (%) of Potatoes When Submerged In Varying Concentrations of Sucrose

Conclusion: The investigation was conducted to verify osmosis by observing the percent change in mass of potato samples after being left in 5 varying concentrations of sucrose (0, 0.1, 0.2, 0.5, 1.0 and 2.0). In general, the effects of the varying concentrations were successfully seen from the percentage change in mass of potato samples. In Graph 1 the trendline displays a negative linear relationship between sucrose solution concentration and percent change in mass of potatoes, therefore as the concentration of sucrose increases, the mass of the potato decreases. When referencing Table 1, one can observe that for the distilled water, there was an 11.14% increase in mass of the potato, meaning the potato gained mass. This can be explained by the principle of osmosis, in which water molecules move from a low solute concentration to a high solute concentration. Understanding this, one is able to discern that since the potato samples in the distilled water, the solution the potato was submerged in was a lower solute concentration than the potato. Furthermore, it is evident from the data that the water is hypotonic (meaning that the total concentration of the solute particles is less than that of another solution), and the potato is hypotonic (meaning that the total concentration of the

solute particles is greater than that of another solution), driving the water molecules from the from the lower solute concentration water to the higher solute concentration potato, resulting in an increase of mass. As the concentration of sucrose is increased to 0.5M, the change in mass is now decreased by -24.11% . Since the change in mass is negative, the sucrose solution must be hypertonic, while the potato must be hypotonic, as water molecules are driven from the lower solute concentration potato sample to the higher solute concentration sucrose solution. With the increase of sucrose solutions from 0.5M onwards, one can note the negative change in mass of the potatoes is greater and greater as the amount of sucrose solution rises. This elucidates the fact that not only do water molecules move from low solute concentrations to high solute concentrations, but they do so in order to reach an equilibrium, in which the two solute concentrations are the same, or isotonic. This is the reason that at 0.5M the change in mass is -24.11%, and the change in mass at 2M is -31.86%. Using Table 1, it is evident that sucrose concentrations of 0M to 0.2M are hypotonic because of the increase of mass in potatoes, and that sucrose concentrations ranging from 0.5M to 2M are hypertonic because of the decrease in mass. With this one could estimate that the isotonic point occurs somewhere between 0.2M and 0.5M concentrations, however using the equation given from the trendline provides for a calculation of more accuracy by solving for ‘x’ when ‘y’ is 0. y =− 9.3777x + 22.894 0 = − 9.3777x + 22.894 x = 2.44 Therefore the potatoes and sucrose solution would be isotonic at 2.44M, and because of this, no water molecules would be needed to move to a higher concentration, therefore the mass of the potato will remain unchanged.

Evaluation: Source of Error

Suggested Improvement

The various sizes, shapes and masses of the potato samples. This has the opportunity to greatly affect the accuracy of our data, potatoes with varied shape, size and mass would have impacted the rate of osmosis, thereby affecting the mass gained or lost.

By specifying the length, width, shape and mass of the potato, as well as using the same equipment to get the potato samples, data across all the groups would become more consistent, and yield a similar set of data. Furthermore, such a specification allows for greater accuracy and precision because the amount of water in the potato sample would be constant.

The texture/ripeness/moldiness of the potato could change the concentration of

By ensuring that came from the same producer of potatoes and that the potatoes were

solute in a potato. This could change the concentration of solute in the potato.

purchased on the same day, the ripeness of the potato should be the same throughout. This could be further controlled by storing all of the potatoes that would be used in the experiment in the same conditions.

The temperature of the room, and thereby the sucrose solutions were not kept constant throughout the experiment, which affects the rate of osmosis. A warmer sucrose solution allows osmosis to happen quicker because the particles are moving quicker, and a colder solution would mean that osmosis happens slower, because particles are moving slower.

This source of error can be controlled by setting a constant temperature in the area that the potato samples are being stored throughout the waiting time....