Osmosis

• Osmosis is the net movement of water molecules from an area of high concentration (dilute solution) to an area of low concentration (concentrated solution) through a partially permeable membrane.
• Water moves from areas of lower solute concentration to areas of higher solute concentration by osmosis.
• No energy is required for osmosis so it is a passive process.
• In plants, water moves by osmosis from a dilute solution in the soil to a concentrated solution in the root hair cell.
• The aim of the osmosis required practical is to immerse plant tissue in a range of concentrations of salt or sugar solution, find the change in length or mass of the plant tissue in order to investigate the movement of water by osmosis into or out of the plant tissue.
• The equipment required for the osmosis required practical is plant tissue (e.g potato), cork borer, ruler, measuring cylinder, labels, boiling tubes, test tube rack, paper towels, sharp knife, white tile, range of sugar or salt solution, distilled water and a top-pan balance.
• Cut 5 potato cylinders so they are about 3cm. Measure and record length and mass. Measure 10cm^3 of 1.0M sugar solution and transfer to a boiling tube. Repeat for the other concentrations and distilled water. Add one potato cylinder to each boiling tube and prepare a results table. Leave overnight. Remove the cylinders from the boiling tubes and carefully blot them dry with a wet paper towel to remove excess water. Measure the length and mass of each cylinder and record in a table. Calculate the percentage change. Plot a graph of change in mass/length against concentration.
• Water may move across cell membranes via osmosis. Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.