The effect of NaCl solutions on the mass of potatoes

Osmosis is a type of diffusion. It requires a concentration gradient and a semi-permeable membrane and, where the molecules of the solute are too big to pass through the membrane. Instead, the water is going to pass through the membrane in order to equal out the concentration of the solute.

There are three types of solutions:

Hypertonic solution

A solution that has higher osmotic pressure (higher amount of solute) than another solution to which is compared

Hypotonic solution

Refers to any solution which has a lower osmotic (lower amount of solute) pressure than another solution

Isotonic solution

One that has the same solute concentration in both solutions

With the help of this experiment, the best environment for the potatoes will be found. This experiment can be used on other vegetables as well, in order to increase the production of the fields.

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Materials used:

1L beaker
6 40mL test tubes
1 100mL measuring cylinder
Test tube rack
Salt
Electronic scale
Two-Three potatoes
Scalpel
Ruler
Distilled water
Oil pen
Paper towels
Aluminum cover

Procedure:

Cut six potato pieces using the scalpel and ruler

Each piece should be rectangular
The size should be 5X1X1

Mass the six potato pieces
Make 6 solutions of NaCl (salt) with different concentrations

Set up a control group

25mL of distilled water in one of the 40mL test tubes
Label the test tube using the ...

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Materials used:

1L beaker
6 40mL test tubes
1 100mL measuring cylinder
Test tube rack
Salt
Electronic scale
Two-Three potatoes
Scalpel
Ruler
Distilled water
Oil pen
Paper towels
Aluminum cover

Procedure:

Cut six potato pieces using the scalpel and ruler

Each piece should be rectangular
The size should be 5X1X1

Mass the six potato pieces
Make 6 solutions of NaCl (salt) with different concentrations

Set up a control group

25mL of distilled water in one of the 40mL test tubes
Label the test tube using the oil pen

Measure 45mL of distilled water using the 100 mL measuring cylinder and sip that water in the 1L beaker
Measure 1g of salt and put in the water in the beaker (2% solution)
Move the water in the beaker around, so that the salt dissolves faster
After the salt is dissolved, pour it back to the measuring cylinder
Pour water until 50mL
Pour 25mL of the water into one of the test tubes
Label the test tube using the oil pen
Repeat the steps b-h using 2g, 3g, 4g and 5g of salt (4%, 6%, 8% and 10% solutions respectively)

Put one potato piece in each test tube
Cover the top of each test tube with an aluminum cover in order to avoid evaporation
After 24 hours, take out the potato pieces
Gently dry the surface using paper towels
Measure the mass of the potatoes

Variables:

Independent variable: % solution

Dependent variable: % mass change

Data

Individual data

Group average

The potatoes gained most mass in 0% solution, and lost most mass in 2% solution. The % mass change decreased with the increase of the % salt solution.

Possible errors and improvements

Possible errors

Potato pieces

First of all, not all of the pieces were perfectly rectangular, which could have affected the osmosis rate
Secondly, some pieces were not long/wide enough, some of them even had the peel on them

Improvements

Larger and sharper knives could have been used, in order to cut more precisely, or, instead, smaller potato pieces could have been used for the experiment

Conclusion

The data of all individuals followed the same general pattern, where the potatoes gained most mass in 0% solution, and lost most mass in 2% solution. The % mass change decreased with the increase of the % salt solution. This means, that potatoes grow best in hypotonic solutions, and they lose mass in hypertonic solutions.

There were not a lot of sources of error, and those possible errors were avoided by several individuals doing the experiment.