RP3

Question 1

Why do you peel off the skin of the potato?

Answer 1

• Cells of skin may have different water potential to the tissue cells
• The peel may not be permeable/ does not allow water to pass through via osmosis
• There are different types of cells in the tissue and skin.

Question 2

Why must the potato cylinders be the same length?

Answer 2

Same length means they will have the same surface area. Therefore there will be no effect on the rate of osmosis.
Different surface area affects rate of osmosis.

Question 3

You were given potato cylinders taken from potatoes of the same variety. Give one reason why this was important.

Answer 3

• Will have the same genetic makeup.
• Have the same water potentials.

Question 4

Why should you not squeeze water out the potato cylinders and only blot them?

Answer 4

• Squeezing out water would lead to an inaccurate measurement of the initial mass/water content.
• Squeezing would disrupts the natural process of osmosis as it removes water directly from the cells.

Question 5

Why do you use percentage change in mass for the results?

Answer 5

Allows the results to be comparable.

Question 6

Describe how you would use your results for 100% (solution) to find the rate of osmosis.

Answer 6

Rate = % change in mass / time

Question 7

EXAMPLE QUESTION :
Describe how you would make 30cm^3 of a 1.6 moldm-^3 solution of fructose solution from a 3 moldm-^3 stock solution of fructose.

Answer 7

30 x 1.6 / 3 =16
OR
3/ 1.6 =1.875 so 30/ 1.875 =16cm^3 of fructose.
So 14cm^3 of water.