Osmosis Lab Report

Rachel Cobb

Background Information

This experiment was used to test the effects of osmosis. In the experiment, three plastic dialysis tubes were filled with distilled water and tied on both ends. The mass of the tubes were measured and recorded. The tubes were then placed in three different kinds of solution: regular dark soda, regular clear soda, and regular drinking water. They were allowed to sit for 24 hours and were then massed again.

Why Was This Experiment Conducted?

This experiment was conducted to test the effects of osmosis on cells depending on whether they were placed in an isotonic, hypotonic, or hypertonic solution. The water-filled tubes posed as the cells and the sodas and water posed as the different types of solutions. The purpose of the investigation was to see if the type of solution in which a cell is placed really does affect the mass of the cell.

Variables In the Experiment

In this experiment, the independent variable was the type of solution in which the water-filled tubes were placed and the dependent variable was the mass of the tubes. The type of solution in which the water-filled tube was placed was also the control variable because it was the only thing that stayed the same. The constants were the things in the experiment that remained the same: the amount of water in the tubes, the type of water inside of the tubes the amount of solution they were placed in, and the amount of time they stayed in the solution.

Hypothesis

If the tubing is placed in a cup of distilled water, then the mass of the tube will decrease because the solutes will leave the tube, but if the tubing is placed in a cup of clear soda, then the mass will slightly increase, and if the tubing is placed in a cup of regular dark soda, then the mass of the tubing will greatly increase.

Materials

  • 3 plastic dialysis tubes
  • 6 short pieces of string
  • 45 mL of drinking water
  • 270 mL each of distilled water, regular clear soda, and regular dark soda,
  • funnel
  • Sharpie or other such marker
  • balance to weigh the tubes
  • 3 plastic drinking cups

Procedure

  1. Using a funnel, pour 15 mL of drinking water into the dialysis tubing. Tie the ends of the tubing with a piece of string. Measure the mass of the tube and record it in a data table.
  2. Repeat step one with two more separate tubes. Label the tubes with numbers and later on, be sure to record which tube number was placed in which solution.
  3. Pour 270 mL of each solution into three separate cups. Be sure to label each cup appropriately.
  4. Put one dialysis tubing into each cup. Record the time that the tubes were placed into the solution.
  5. Let the cups sit for 24 hours.
  6. Take the tubes out of the cups and pat them dry.
  7. Measure the mass of each tube again and record it in the data table.

Data

Before being placed in the regular clear soda, tube #1 weighed 13.1 grams; after being left in the regular clear soda for 24 hours, it weighed 9.6 grams. Before being placed in the regular dark soda, tube #2 weighed 17.5 grams; after being left in the regular dark soda for 24 hours, it weighed 13.3 grams. Before being placed in the distilled water, tube #3 weighed 14.6 grams; after being left in the distilled water for 24 hours, it weighed 14.7 grams.

Conclusion

The group hypothesized that, if the tubing is placed in a cup of distilled water, then the mass of the tube will decrease because the solutes will leave the tube, but if the tubing is placed in a cup of clear soda, then the mass will slightly increase, and if the tubing is placed in a cup of regular dark soda, then the mass of the tubing will greatly increase. The group concluded that the regular clear soda and the dark soda were hypertonic solutions since they made the mass of the tubes decrease, and the distilled water was a slightly hypotonic solution since it made the mass of the tube increase slightly.