Bio T1-Investigating Osmosis

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  • Investigating osmosis
    • 1.) Prepare sucrose (sugar) solutions of different concentrations ranging from pure water to very concentrated sucrose solution
    • 2.) Use cork borer to cut potato in same size pieces (1cm in diameter from same potato)
    • 3.) Divide potato cylinders into groups of 3 use mass balance to measure mass of each group
    • 4.) Place 1 group in each solution, leave for 40 mins (make sure all get same amount of time)
    • 5.) Remove potato cylinders, pat dry with paper towel to remove excess water from surface to get more accurate final mass
    • 6.) Weigh each group again & record results
    • Interpreting results
      • Calculate percentage change in mass for each group of cylinders (before & after time in sucrose solution)
        • Percentage change =
      • Plot a graph & analyse results
        • At points above x axis water concentration of sucrose solution is higher then in potato cylinders so they gain mass as water is drawn in by osmosis
        • At points where no change in mass ( curve crosses x axis) fluid inside cylinders & sucrose solution are isotonic (have same water concentration
        • At points below x-axis water concentration of the sucrose solutions is lower than in cylinders causes cylinders to lose water so mass decreases

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