Required practical: osmosis on plant tissue

Question 1

Step 1

Answer 1

Peel a vegetable eg potato to remove skin

This is because the skin can affect osmosis

Question 2

Step 2

Answer 2

Use a cork borer to produce 3 cylinders of potato in order to have the same diameter
This makes sure all the cylinders are the same diameter

Question 3

Step 3

Answer 3

Use a scalpel to trim the cylinders to the same length, around 3cm

Question 4

Step 4

Answer 4

Measure the length and mass of each cylinder using a ruler and top pan balance

Question 5

Step 5

Answer 5

Place each cylinder into a test tube with 10cm3 liquid
1st = has 0.5 molar sugar solution
2nd = a 0.25 distilled sugar solution
3rd = distilled water

Question 6

Step 6

Answer 6

Leave potatoes overnight

Question 7

Step 7

Answer 7

Remove potatoes and remove any surface moisture (DO NOT PRESS BUT ROLL)

Question 8

Step 8

Answer 8

Measure the length and mass of the cylinders again

Question 9

Step 9

Answer 9

Calculate percentage increase of the potatoes.

Question 9

Why use distilled water rather than normal water?

Answer 9

Contains no dissolved substances that affect the rate of osmosis

Question 10

Why do we roll the potatoes rather than pressing it?

Answer 10

We want to remove surface water not water inside it

Question 11

Results of distilled water potato

Answer 11

Higher increase in mass as it’s a dilute solution
So water moves into the potato

Question 12

Result of the 0.5 mol sugar solution potato

Answer 12

Decrease in mass as it’s a concentrated solution so water moves out of the potato into the water

Question 13

If you were to plot this on a graph, where the line crosses the x axis what does that mean?

Answer 13

No change in mass
So that means no osmosis = concentration outside the cell is same as concentration inside