An Experiment to find out the effect of osmosis on potato cells
Plan
Apparatus:
- A borer
- 25 test tubes
- 5 test tube racks
- 2 potatoes
- A ruler
- A sharp knife
Variables: Four different sugar solutions at 10%,20%,30%and40% and distilled water
Hypothesis: I hypothesis that the higher the sugar the less the potato size will increase. I think this because I think it will be harder for the liquid to get in because it is denser.
Using the borer make cuts into the potato and pull out the pieces of potato. Chop the pieces so they are 20mm long repeat process 25 times. This experiment must be statistically viable i.e. the potato pieces must be identical. If you come to a bad piece of potato discard it. Put all the pieces into individual test tubes. Using one of the solutions fill up 5 test tubes to exactly the same height. Repeat process for all the solutions. Put test tubes into racks and leave for 24 hours. This should be done as quickly as possible to ensure each piece of potato is immersed for exactly the same period of time.
Research
Fig 1
Osmosis is the transfer of a liquid solvent through a semi permeable membrane that does not allow dissolved solids (solutes) to pass. Osmosis refers only to transfer of solvent; transfer of solute is called . In either case the direction of transfer is from the area of higher concentration of the material transferred to the area of lower concentration. This spontaneous migration of a material from a region of higher concentration to a region of lower concentration is called diffusion. Osmosis will occur if a vessel is separated into two compartments by a semi permeable membrane, both compartments are filled to the same level with a solvent, and solute is added to one side. The level of the liquid on the side containing the solute will rise as the solvent flows from the side of its higher concentration to the side of lower concentration. If an external pressure is exerted on the side containing the solute, the transfer of solvent can be stopped and even reversed (reverse osmosis). Two solutions separated by a semi permeable membrane are said to be isotonic if no osmosis occurs. If osmosis occurs, transfer of solvent is from the hypotonic solution to the hypertonic solution, which has the higher osmotic pressure.
The minimum pressure necessary to stop solvent transfer is called the osmotic pressure. Since the osmotic pressure is related to the concentration of solute particles, there is a mathematical relationship between osmotic pressure, freezing-point depression, and boiling-point elevation. Properties such as osmotic pressure, freezing point, and boiling point, which depend on the number of particles present rather than on their size or chemical nature, are called colligative properties. For dilute solutions the mathematical relationship between the osmotic pressure, temperature, and concentration of solute is much like the relation between pressure, temperature, and volume in an ideal gas. A number of theories explaining osmotic pressure by analogy to gases have been devised, but most have been discarded in favor of thermodynamic interpretations using such concepts as the entropy of dilution.