test for concentration/water potential of cell sap in potato/eggplant Flashcards
what is the definition of osmosis?
the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane
to test for concentration/wp of a cell sap of a potato/eggplant
1.?
use a knife and cut out 10 strips of potato/eggplant slices (6cmX0.5cm)
record down the initial length of the strips in a suitable table
2.?
prepare 50cm3 of sucrose solutions of different concentrations (0.2,0.4,0.6,0.8,1.0 mol/dm3)
3.?
prepare 5 petri dishes for the 5 different concentration and label them according to its concentration of the sucrose solution
add 2 of the strips into each petri dish
4.?
pour each sucrose solution into the respective Petri dish and make sure the all the strips are completely immersed in the solution and separated from one another
5.?
use a stopwatch to time them for 20 minutes
6.?
after 20 minutes, remove the strips from the solutions and dry them using a paper towel before measuring the length of each strip
7.?
record all the measurements into the table and calculate the change in length for each potato strip then calculate the average change in length of the 2 strips
8.?
plot a graph of the average change in length of each 2 strips against the concentration of the sucrose solution
THE CONCENTRATION OF THE CELL SAP IS ON THE XAXIS
why is the concentration of the cell sap on the x-axis/when the change in length is 0?
both the solution and the strip has equal wp so there is no net movement of water molecules and thus no change in length
what are the sources of error?
1) the strips of the potato come from different potatoes so they have different wp and concentration
2) water may evaporate from the sucrose solution during the 20 minutes so it affects the concentration of the solution
