Surface area and osmosis


Large potato,
Sharp knife,
Chopping board
Paper towels
Scales (0.1g resolution)
Beakers x 4
Tea strainer


Carefully cut four cubes of 2cm sides from the potato – ensure they have no skin on.
Leave one cube whole,
Cut one in half to make two 2x2x1cm blocks.
Cut one in four to make four 2x1x1cm blocks.
Cut one in eight parts to make eight 1x1x1 blocks.

Dry and weigh each set of potato pieces and record the masses in a table.

In four beakers with 100ml of water in place each set of potato pieces and start the stopclock.
Time for 10 minutes and then pour each beaker out through a tea strainer – dry and weigh the pieces again.

Use your data to work out the surface area exposed in each case and the percentage mass increase of the potato.


Knife must be used carefully – keep fingers well away from cutting surface. Glass beakers could break if not handled well, plastic beakers could be used for this experiment without any adverse effects.