osmosis Flashcards
what will you do in this practical?
prepare samples of potato and place them in different concentrations of sugar or sodium chloride (salt) solution
* make measurements of the mass and length of your samples before and after soaking them in the
solutions.
step 1
Use a cork borer to cut five potato cylinders of the same diameter
step 2
Use the knife to trim off any potato skin on each potato cylinder. Then trim each potato cylinder using a scalpel so that they are all the same length. (around 3cm)
step 3
measure the length of each cylinder using a ruler and measure the mass of each cylinder using a balance
step 4
Measure 10 cm3 of each concentration of sugar or salt solution and put into boiling tubes.
Label each boiling tube clearly.
what are the different concentrations of sugar solution
tube 1 = 1.0 mol/dm cubed
tube 2=0.75 mol/dm cubed
tube 3= 0.5 mol/dm cubed
tube 4= 0.25 mol/dm cubed
tube 5= distilled water
step 5
Add one potato cylinder to each boiling tube.
step 6
Leave the potato cylinders in the boiling tubes for a chosen amount of time.
(overnight to allow osmosis to take place)
step 7
Remove the potato cylinders from the boiling tubes and carefully blot them dry with the paper towels.
why do you dry potato using paper towels?
to remove any surface moisture
final step
Measure the new mass and length of each potato cylinder again. Record your measurements for each concentration in your table.
calculate percentage change
change in value/original value x 100
what happened to potato in distilled water?
potato cylinder gains mass as water moves into it by osmosis
what happened to potato in concentrated sugar solution?
cylinder lose mass as water moves out by osmosis
