diffusion and osmosis

    Cards (14)

    • What is diffusion?
      The movement of particles from an area of higher concentration to an area of lower concentration.
    • What is a concentration gradient?
      The difference in concentration.
    • The bigger the concentration gradient...
      the faster the diffusion rate.
    • What will give a faster diffusion rate?
      • High temperature- the particles have more energy so will move faster.
      • A bigger concentration gradient.
    • How do dissolved substances move in and out of cells?
      By diffusion through the cell membrane.
    • What happens to the rate of diffusion if the surface area of the membrane increases?
      It increases because more particles can pass through at once.
    • What is osmosis?
      Osmosis is the movement of water molecules from a
      region of higher water/solute concentration to an region of lower water/solute concentration across a partially/semi-permeable membrane.
    • What is a partially permeable membrane?
      One with very small holes in it, only tiny molecules can pass through it e.g water.
    • Can the water pass through both ways of the membrane?
      Yes, as water molecules move randomly all the time.
    • Osmosis required practical.
      1. Cut up a potato into identical cylinders.
      2. Then get some beakers and fill them different sugar solutions (one should be pure water and another should be a very concentrated sugar solution e.g 1mol/dm3dm^3)
      3. Measure the mass of each cylinder and record it on a table then place one potato cylinder in each beaker for 24 hours.
      4. Then take them out and dry them using a blue paper towel and measure their new mass.
      5. Repeat the experiment and calculate a mean percentage rate of each concentration.
    • How does the mass of the potato change?
      • If water has been drawn in by osmosis the mass increases.
      • If water has been drawn out the mass decreases.
    • What is the dependent variable of the of the practical?
      The mass of the potato.
    • What is the independent variable of the osmosis practical?
      The concentration of the sugar solution.
    • What are the control variables of the osmosis practical?
      • The volume of the solution.
      • The time each cylinder has been in the solution for.
      • Type of sugar used.
      • Temperature of the room and solution.