osmosis

• osmosis is the movement of water molecules across a partially permeable membrane (holes only tiny molecules can fit through e.g water) from a region of higher water concentration to a region of lower water concentration,

  there will be a net flow of water molecules into the region with a lower water concentration (sugar solution), and the solution will become more dilute.
• osmosis practical on plant tissue (method):

  1. cut a potato into cylinders, measure there mass and put them in beakers with different sugar solutions (one water, one very concentrated etc),
  2. leave for 24 hours,
  3. take the potatoes out dry and re-measure the mass,
  4. if theyve drawn water in by osmosis there mass will have increased, if there waters been drawn out there mass will have decreased
• osmosis practical on plant tissue (variables):

  1. independent variable (thing altered)- the concentration of the sugar solution
  2. dependent variable (thing measured/tested) - potato mass
  3. control variable (thing kept the same) - temprature, time, etc
• osmosis practical on plant tissue (errors):

  may happen when doing the method (e.g if waters evaporated from the beakers and the solution concentrations changed)

  reduce the errors effect by repeating the practical and calculating a mean percentage change.