Osmosis Experiment Planning
Osmosis is the passage of water molecules from a weaker solution into
a stronger solution, through a partially permeable membrane. In this
case, the tiny holes in the membrane of the potatoes will allow the
water molecules to pass through in and out of the solution and the
potato, depending on the concentration gradient of the two substances.
So in this case, when the water concentration is lower in the tissue,
the water will go inside the tissue of the potato, and the potato will
grow in length, and if there is very little difference in the two
water concentrations, there shouldn't be such a big change in length.
If there is a higher concentration of water in the potato, the water
will go out of the potato. Water molecules have random kinetic energy
meaning they move around where they want and wherever they want.
The potato, cut up into pieces, will need some sort of element to
survive, and in this experiment, it would be light and water. With
both of these sources, the potato will keep on working, until it dies
of either lack of water, too much water. When the concentration
gradient is lower in the potato, the water will transfer from the
solution to the potato.
The chip will not continue to grow in size because the cell wall will
stop expanding when all the cells become turgid. When the change in
length is 0 it means that the concentration gradient inside the
cylinder is the same as that outside the cylinder. This is known as
osmotic equilibrium and means that the exact same amount of water
particles are moving in to the cells as those which are leaving the
cells, thus telling us there is no change in length whatsoever.
Water potential is determined by measuring hydrostatic pressure and
osmotic pressure. Using an experiment like those below, we can
determine that water potential is when the line crosses the x axis on
Apparatus - White tile - to cut potato on
- Blade/knife - to cut the potato to specific lengths
- 5 test tubes in rack - to place experiments in
- Potato - to use in the experiment
- Sucrose - to use in the experiment
- Distilled Water - to use in the experiment
- Cork borer - to create the potato cylinders
- Stop clock - to time the experiment
- 25cm³ measuring cylinder - to measure the solutions
- Callipers - to measure the length of the potato to 0.1mm
Method - We took a potato and then used the cork borer to create
multiple cylinders of potato. We then cut these to 30mm lengths on the
white tile using a blade and callipers. The ends of the cylinders were
cut square so that they were all equal in size. In the first test tube
20cm³ of distilled water was...