Practical: Observing Diffusion and Osmosis
Strand 1: SA1, SA2
Date:
Name:
INTRODUCTION:
Diffusion is the movement of gas or solute molecules from a region of higher concentration
to a region of lower concentration until they are spread out equally.
Osmosis is movement of solvent molecules (usually water) from the region of their higher
concentration to the region of their lower concentration through a selectively permeable
membrane.
INSTRUCTIONS:
 Carry out these two practicals on diffusion and osmosis and fill in the blank spaces.
MATERIALS:
2 x 500ml Beakers
Large glass funnel
Potassium Permanganate crystals
1 Large Potato
Potato peeler/scalpel
2 x Pins
Concentrated Sucrose/Sugar solution
1
AIM: To observe diffusion.
METHOD:
1. Fill a beaker with water and allow it to stand for a while so that water movement
stops.
2. Place a large funnel into the water so that it touches the bottom and drop a few
small crystals through the straw. Remove the funnel carefully and slowly.
3. Observe the area that is coloured by the potassium permanganate at the beginning
of the experiment, after 15 minutes and then after 30 minutes and shade in these
areas in the beakers printed in the table below.
RESULTS:
Beginning of experiment
After 15 minutes
After 30 minutes
CONCLUSION:
The potassium permanganate moved from an area of ________________ concentration
to an area of _________________ concentration until its particles were equally spaced
throughout the solution (until they were in equilibrium).
QUESTION:
Explain how using hot water would affect the results of this experiment (remember that
when you explain you need to give a reason for your answer).
2
AIM: To predict the direction of osmosis.
METHOD:
1. Peel off the skin of a large sized potato with a scalpel/potato peeler.
2. Cut its one end to make the base flat.
3. Make a hollow cavity in the potato almost up to the bottom of the potato.
4. Add sugar solution into the cavity and mark the level by inserting a pin at the level of
the sugar solution (insert the pin at an angle into the cavity at the level).
5. Place the potato in the beaker containing water.
6. Observe what happens to the level of the sugar solution in the potato.
RESULTS:
DISCUSSION:
(Explain your observations)
CONCLUSION:
Water moves from an area of ___________________ concentration (the water in the
beaker) to an area of ____________ concentration (the sugar solution in the potato)
through the selectively permeable membranes of the potato cells until equilibrium is
reached.
3