Osmosis is the net movement of water from a dilute solution to a more concentrated solution through a partially permeable membrane.
Dilute means less dissolved solute and a higher concentration of water. Concentrated means more dissolved solute and a lower concentration of water.
Water molecules move both ways, but there is net movement towards the concentrated solution. No energy from respiration is needed.
Water enters by osmosis. Potato tissue gains mass. Plant cells become firm (turgid) as water fills their vacuoles.
Water leaves by osmosis. Potato tissue loses mass. Plant cells lose firmness.
Investigate how sugar or salt concentration affects the mass of plant tissue.
Keep the potato source consistent. Use cutting tools as your teacher directs.
Example: 5.0 g becomes 5.5 g. Change = +0.5 g.
Positive means a gain; negative means a loss. Percentages allow fairer comparisons when starting masses differ.
Put solution concentration on the x-axis and mean percentage mass change on the y-axis.
Where the graph crosses 0% change, there is no net movement of water. This estimates the concentration that balances the potato tissue.
Average rate of water uptake can be estimated from mass gain over time.
If a cylinder gains 0.6 g in 30 minutes, the average rate is 0.02 g/min.
Water moves from dilute to concentrated solution through a partially permeable membrane. Mass gain means water entered; mass loss means water left.
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