osmosis

Question 1

1. What is Osmosis?

Answer 1

The net movement of water from an area of high water potential to an area of low water potential, through a partially permeable membrane.

Question 2

2. Compare and contrast how water and ions enter cells.

Answer 2

Comparison: both move down concentration gradient; Comparison: both move through protein channels in membrane; Contrast: ions can move against a concentration gradient by active transport

Question 3

3. Give two similarities between diffusion
   and osmosis

Answer 3

Movement is down a concentration gradient; Both are passive processes;

Question 4

4. What is the highest water potential? And
   what happens when you add a solute?

Answer 4

Pure water has a water potential of 0. When any solute is added the solution becomes more negative.

Question 5

5. When investigating osmosis, why do you
   need to blot the potato before weighing it?

Answer 5

Water will affect the mass, and we only want to measure water taken up or lost; Amount of water on cylinders varies so it ensures same amount of water on outside;

Question 6

6. How do you calculate the volume of stock
   solution needed?

Answer 6

Concentration needed x volume needed Concentration of stock solution

Question 7

7. Why do we calculate the percentage
   change/a ratio of initial to final mass?

Answer 7

Allows comparison or shows proportional change; As the cylinders have different starting masses;

Question 8

8. Why does repeating the experiment improve reliability?

Answer 8

A mean can be calculated; the effect of anomalies can be minimised by identifying them and discarding;

Question 9

9. Describe how you would use the student’s results in the table above to find
   the water potential of the potato tissue.

Answer 9

Plot a graph with concentration on the x-axis and percentage change in mass on the y-axis; Find the concentration where percentage change is zero; Use a table to find water potential of solute concentration where curve crosses x-axis.

Question 10

10. Explain why a chipped potato would loss
    mass in a salty solution

Answer 10

Water potential of solution is more negative than that of potato tissue; Tissue loses water by osmosis;