GCSE Biology (AQA)

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Percentage Gain & Loss of Mass

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Cell Biology Transport in Cells

Percentage Gain & Loss of Mass

4:47 Osmosis
Spec 4.1.3.2
Previous Rate of Water Uptake Next Defining Active Transport
  • Measure percentage gain and loss of massive plant tissue using a formula: (mass at end - mass at start) / mass at start * 100.
  • Change in mass can be either positive or negative, indicating mass gain or loss.
  • Memorize the formula for exams to measure percentage changes in plant tissue.
  • Practical example using potato cylinders placed in different sucrose solution concentrations to observe changes due to osmosis.
  • Initial mass of potato cylinder was 2.4 grams; after exposure to a 0.6 M sucrose solution for one hour, it lost 0.4 grams.
  • Percentage change in mass calculated as -16.7%, indicating a loss in mass.
  • Experiment repeated at various sucrose concentrations to gather comprehensive data on how mass changes with sucrose concentration.
  • Positive values indicate water gain (increase in mass), negative values indicate water loss (decrease in mass).
  • Graphical representation shows that as sucrose concentration increases, the change in mass generally decreases due to more water loss by osmosis.
  • At certain sucrose concentrations (0.25 to 0.3 M), no net osmosis occurs, indicating isotonic conditions relative to potato cells.
  • Ability to draw and interpret graphs of percentage gain or loss in mass against sucrose concentration is crucial for exams.

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