Osmosis in a potato

O/L Science · G.C.E. Ordinary Level · Grades 10–11

Aim

To demonstrate osmosis with potato strips and find the isotonic concentration.

Apparatus

• Potato strips
• Sucrose solutions of different concentration
• Balance and beakers

Method

1. Cut equal potato strips and weigh each.
2. Leave each in a different solution for 1 hour.
3. Remove, blot dry and weigh again.
4. Calculate the % change and plot it against concentration.

Conclusion

Strips in dilute solutions gain water and mass; in concentrated solutions they lose it. The concentration with no change (where the graph crosses the x-axis) is the isotonic concentration.