B3.1.1 Dissolved substances

Water often moves across boundaries by osmosis. Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules.

Differences in the concentrations of the solutions inside and outside a cell cause water to move into or out of the cell by osmosis.

Most soft drinks contain water, sugar and ions. Sports drinks contain sugars to replace the sugar used in energy release during the activity. They also contain water and ions to replace the water and ions lost during sweating.

If water and ions are not replaced, the ion / water balance of the…