Potato's Osmolarity Lab Report

Silvia Chen

Result

[pic 1]

Plot a graph of sucrose concentration vs percent mass change

[pic 2]

Describe the trend in the graph.

The trend is linear. There is an inverse relationship between the sucrose concentration and the percentage mass change. As the sucrose concentration increases, the percentage mass change will decrease.

The value of R2, 0.8958, indicates the strong correlation between the two variables.

What does this tell you about the concentration of solutes in the potato?

    At the isotonic point that potato has zero percentage change in mass, the concentration of sucrose solution is equal to the concentration of solutes in the potato.

    According to the linear trend line equation(y=-33.75x+17.019), when the average percent change in mass (y) equals zero, the sucrose concentration(y) is 0.504 mol/dm3, so concentration of solutes in the potato is 0.504 mol/dm3.

Conclusions

1. Explain why the rate of uptake or loss of water from the potato tissue varied according to the concentration of the solution in which it was immersed.
2. Suggest factors which might affect the results that you obtain for different potato samples.

Osmosis is the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration, across a partially permeable membrane. Osmolarity is the number of moles of solute particles per unit volume of solution.

As osmosis is a kind of passive transport, it is based on the concentration gradient. If the gradient is huge, the rate of osmosis will increase, and vice versa.

When the concentration of the solution is lower than the osmolarity of the potato tissue, the surrounding solution is hypotonic, and the rate is positive that the water will move by osmosis from the outside solution to the potato tissue. Lower the concentration of outside solution is, higher the rate is.

When the concentration of solution is higher than the osmolarity of the potato tissue, the surrounding solution is hypertonic, and the rate is negative that the water will move by osmosis from the potato tissue to the outside solution. Higher the concentration of outside solution is, lower the rate is.

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