RP osmosis Flashcards
% change equation
change in mass (g)/starting mass (g) x100
rate of osmosis equation
change in mass (g)/time (min)
list each of the variables in the RP
independent-concentration of sugar solution
dependent-mass of potato
control-volume of salt solution, size of potato
what were the results?
potato in low concentration-gain mass (hypotonic)
medium concentration-stay the same (isotonic)
high concentration-lose mass (hypertonic)
what has happened to the water when the potato increased in mass?
the water has diffused in to the potato
why does water diffuse out at a high concentration?
because it moves from a high concentration area to a low concentration area
list two errors that may occur, and the result of them
- potato cylinder was not fully dried (excess water would give a higher mas)
- water evaporated from the beaker (concentration of solution would change)
state the method
- Cut up a potato into 5 identical cylinders using a cork borer
- Fill 5 beakers with 10cm³ of different sugar solutions. One should be distilled water and the concentrations of the rest of the solutions should be 0.25, 0.5, 0.75 and 1 mol/dm³.
- Weigh each potato cylinder and make note of each mass, measure length and make a note
- Place the one potato into each beaker and leave for 24 hours.
- Remove the potato cylinders and dry them with a paper towel.
- Reweigh and remeasure the potato cylinders and calculate the percentage change in mass.
rate of osmosis
the rate at which water moves across a semi-permeable membrane
equipment
-potato
-cork borer
-ruler
-measuring cylinder
-boiling tubes
-paper towels
-range of sugar solutions
-distilled water
safety
sharp knife/cork borer
why is it necessary to use a cork borer?
results in equal sized samples so changes in length and mass can be compared easily
why do you blot the potatoes with paper towels?
allow excess water to be removed, more comparable mass
