Osmosis Experiment Lab Report

Yara Mneimneh
Ms. Nasrin Vali
Biology 11 B
9. October. 2016
Osmosis Investigation
Introduction
Osmosis is the passive movement of water molecules across a selectively permeable membrane, from a region of low solute concentration to a region of high solute concentration. Osmosis is different than diffusion, since the net movement of the water is due to the solute concentration rather than the molecules.

In this experiment, two types of solutions will be tested to examine the effect on osmolarity. Sodium chloride solution will be tested and distilled water will be tested, both on red onion cells. Sodium chloride contains particles which makes it have more of a higher concentration in correlation to a plant cell.

Red onions will be tested

This will be the only type of cell used in the experiment.

Procedure
To create the sodium chloride solution:
Measure 15 grams of salt (table salt), using an electronic balance. The percentage of sodium chloride that will be added to water to create a solution is 15%.
Pour 100 milliliters of water (distilled) in a glass graduated cylinder with an uncertainty of 100 ml +- 0.1 ml, add the 15 grams of salt into the cylinder.
Using a stirring rod, stir the salt with the solvent, until it becomes a solute solution. This is part of the independent variable. It will be used to bathe one of the tissues and after calculating the final mass change then it will be determined if this solution impacted the red onion cells’ osmolarity.
Label this cylinder A.

Procedure
Firstly, cut through the middle of the red onion, creating two halves. The red onion will be the only onion and type of cell used for this experiment. This will be controlled by using two tissues from the same cell.
Observing the two halves, use a tweezer to remove a thin slice (about 0.5 inches in depth and 1.5 inches in length and width) from the inner layer of the onion. The piece removed will represent the

Remove the two tissue samples from their bathing solutions.
Dry them using a paper towel or with a piece of soft cloth. Measure each tissue again separately to find the final mass of each tissue.
Calculate the mass change of each tissue sample. Formula: % change = (final mass - initial mass/initial mass)/initial mass x 100. The percentage of the mass will be calculated to determine if the water and sodium chloride solution affected the onions’ osmolarity. 12. Plot the results on a graph about the effect of two different solutions on red onion cells. 13. Repeat steps 1-4 of the sodium chloride solution making and steps 1-12, for 15 trials.

Cautions and Warnings
Make sure the electronic balance is set to zero, before placing the tissue on it to measure the initial mass, as the estimate will be inaccurate if this step is not followed.
If the initial mass of the second tissue differs from the first tissue, make sure to make adjustments to create two equal tissues.
For safety issues, make sure there is a far distance between your fingers and the end of the tweezer when removing the tissue, to avoid a cut or