osmosis

• osmosis is the movement of water molecules across a partially permeable membrane from high to low water concentration
• water moves both ways through the membrane because water molecules move randomly all the time
• which way does water move through a membrane?

  both ways
• why do water molecules move both ways?

  because they move randomly all the time
• due to water being more on one side it has a steady net flow to the other
• | plant tissue & sugar solution [practical]

  1. cut potato into identical cylinders in different sugar solutions_ one in pure water, the other in very concentrated sugar solution
  2. measure mass of cylinders and leave one cylinder in each beaker
  3. take them out, dry & measure masses again
  4. if they've drawn in water, they'll increase in mass_ calc % change in mass & plot

  • DEPENDENT VARIABLE: chip mass
  • INDEPENDENT VARIABLE: concentration of sugar solution
  • CONTROLLED: volume, temperature, time, sugar used
  • errors: potato not fully dry, water evaporated
  • reduce them by repeating experiment & calc mean % change