required practical 3: produce a dilution series of a solute

Question 1

how do you calculate dilutions

Answer 1

C1XV1= C2XV2

Question 2

how do you produce a calibration curve to identify water potential

Answer 2

create a series of dilutions
cut plant tissue into squares - same size -
blot dry with paper towel and record initial mass
immerse sample into solution for a set time in a water bath - temp of 30 degrees -
remove and blot dry, record final mass
calculate % change
graph: concentration on x axis and %change on the y axis
the x intercept = water potential

Question 3

why do you work out % change of mass

Answer 3

to allow for comparison as they may have different start masses

Question 4

why was sample blotted dry before weighing

Answer 4

any solution will add to mass, the amount of solution will vary in each cube

Question 5

explain what happens to plant tissue when in different concentrations of solute

Answer 5

increase in mass - water moves in by osmosis as there was a higher water potential outside the cell
decrease in mass - water moves out by osmosis as there was a lower water potential outside the cell
no change in mass - no net movement of water by osmosis