OSMOSIS LABWhitney Dougherty, Divya Arcot, Kelly Christensen,

Molly Horton

Period 4

What is Osmosis?Osmosis is the diffusion of water from areas

of higher concentration to areas of lower concentration. (From hypotonic solutions which contain less of the solute to

hypertonic solutions which contain less of solvent)

This takes place in order to maintain homeostasis within cells.

PurposeTo determine how varying the type of food

and amount of salt concentration affects osmotic regulation.

Procedure1. Cut potato & apple

(approximately 1cm)2. Weigh samples in grams3. Place in variable salt

solutions*4. Sit for 30 minutes5. Removes samples, dab dry, &

re-weigh6. Record data & analyze results

*see next page

Salt

Procedure (continued)

How to make a salt solution:1. Measure 50 mL of distilled water 2. Measure the amount (in grams) of salt,

which will be the same number as the percentage of salt in the solution (ex. 5 grams for a 5% salt solution)

3. Pour the salt into 50 mL of the solvent4. Stir solution until the salt is visibly dissolved5. Add 50 mL of the solution, so that you have a

total of 100 mL of the solution.

Procedure (continued)

Controls Variables

Size of samplesAmount of solvent (H2O)Time

Type of food

Salt Concentration

VS.

Distilled H20

1% Salt

5% Salt

10% Salt

HypothesisBecause apples and potatoes are composed

of different materials, their chemical properties differ. These characteristics will in turn cause variations in their rates of osmosis. The rates of osmosis of the apple and potato samples will also vary in different manners when the samples are placed in salt solutions.

PredictionWe think the potato will have a higher rate of

osmosis because they are more dense due to their starch concentration. In comparison, apples are less dense and have a higher concentration of water.

DataDistilled

H20(g)

1% salt (g)

5% salt (g)

10% salt (g)

PotatoINITIAL

2 2.1 1.9 2.2

FINAL1.2 1.3 1.5 1.5

AppleINITIAL

1 1.1 1 1

FINAL.7 .6 .7 .8

Percent Change in MassEQUATION

MassInitial – MassFinal

_______________________________ X 100

MassInitial

Distilled H2O

(% grams)

1% Salt Solution

(% grams)

5% Salt Solution

(% grams)

10% Salt Solution

(% grams)

Potato

66.67 61.54 26.67 46.67

Apple 42.86 83.33 42.86 25

Percent Change in Mass(Graphed)

0 2 4 6 8 10 12

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0Potato Percent Change

Potato percent change (g)

Molarity (mol/L)

Perc

ent

Change (

g)

0 2 4 6 8 10 12

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0Apple Percent Change (g)

Apple Percent Change (g)

Molarity (mol/ L)

Perc

ent

change (

g)

ConclusionThe purpose and corresponding results:

The purpose of this lab was to observe the effects of food types on osmotic rates in various salt solutions.

Our data showed that our prediction was correct. It showed that the potato had a higher rate of osmosis than the apple.

ConclusionWhat could have gone wrong?

Although our prediction was correct, the results of our data were inconclusive, as they did not exactly follow theory. We believe this was due to:1. Potential contamination of the distilled water

as the data collected from the other solutions followed the osmotic theory.

2. Denatured aquaporin pumps which facilitate the flow of water into the cells of the food samples.

3. The fact that samples were taken from foods which had been sitting out for a while.

ConclusionWhat We Learned:

We learned how the cell membrane of different foods respond in a similar fashion to variable salt concentrations of a solvent.

Since our results were inconclusive, the best method of action is to re-do the experiment. In this way, we would be able to test whether the distilled water was actually distilled and verify the consistency of the rest of our results which followed osmotic theory.