Osmosis Flashcards
Define osmosis
Movement of water molecules across a partially permeable membrane from region of high water concentration to a region of low water concentration
What is a partially permeable membrane
Direction water molecules move in ?
one with very small holes - only small molecules can pass like water but not large molecules .
Water molecules move both ways through membrane during osmosis . This happens as water molecules move around randomly all the time. This means strong sugar solutions get more dilute . The water acts like its trying to even up concentration either side of the membrane.
Osmosis is a type of diffusion -
passive movement of water particles from region of high water concentration to a region of low water concentration
Effects of sugar solutions on plants tissues - PRACTICAL
1) Cut a potato into identical cylinder and get beakers of different sugar solutions, one should be pure water, one should be very high concentrated sugar solution and few other should be in between concentrations.
2) Measure mass of cylinders and leave the cylinders in each beaker for around 24 hours
3) take them out , dry them with paper towel and measure masses again
Effects of sugar solutions on plants tissues - PRACTICAL
If cylinders drawn in water, and drawn out by osmosis ..
water drawn in = increase in mass
water drawn out = decrease in mass
4) You can plot % change in mass and plot a few graphs
5) Dependent variable = chip mass
independent variable - concentration of sugar solution
Other variable ( temperature ,time ) must be kept the same in each case or experiment won’t be fair
6) Errors may arise when carrying out method e.g. if cylinder not fully dried, excess water may add mass or if water evaporates from beaker, concentration of sugar solutions may change . You can reduce the effect of these errors by repeating the experiment and calculating mean % change at each concentration
