Handout: Explaining the Gummy Bear Observations
In the gummy bears, the sugar could not move into and out of the bears easily – probably
because of the presence of the gel. Instead, it is the water moving from an area of high
concentration – of water – to an area of lower concentration – of water. The gummy bears
plumped up the most when they were placed in water. This is because the concentration of water
outside the bear was much higher than the concentration of the water inside the bear. The water
will continue to move until the concentrations of substances inside and outside of the bear are
the same. When the bears were placed in a solution with a high concentration of sugar, the bears
only plumped up a little. When the bears were placed in a solution with a concentration of sugar
higher than that of the bear, the bear became smaller. In the case of the corn syrup, the
concentration of water inside the bear was actually higher than the concentration of water
outside of the bear at the beginning of the experiment.
Dots represent sugar molecules. Arrows show the direction of water movement.
Handout: Osmosis / Diffusion
• Osmosis is the movement of water across a selectively permeable
membrane from an area of high water potential (low solute concentration)
to an area of low water potential (high solute concentration).
• Osmosis is a passive process, like diffusion which describes the spread of
particles through random motion from regions of higher concentration to
regions of lower concentration.
• Net movement of solvent is from the less-concentrated (hypotonic) to the
more-concentrated (hypertonic) solution, which tends to reduce the
difference in concentrations.
• The osmotic pressure is defined to be the pressure required to maintain an
equilibrium, with no net movement of solvent. Osmotic pressure is a
colligative property, meaning that the osmotic pressure depends on the
molar concentration of the solute but not on its identity.