Passive transport occurs when a substance passes through the cell membrane without needing any energy to pass through. This happens when a substance moves from an area where it is more concentrated to an area where it is less concentrated. Concentration is the number of particles of a substance in a given volume. Let's say you dissolve a teaspoon of salt in a cup of water. Then you dissolve two teaspoons of salt in another cup of water. The second solution will have a higher concentration of salt. A man put two cups, cup A and cup B, filled with equal amounts of water on to a table and walked away to go check his mail. His son came along and saw the two cups and decided to put some sugar in them to make a tasty drink. The child poured two spoonfuls of sugar into cup A and three spoonfuls of sugar into cup B. Which cup has a lower concentration of sugar?
The answer to this question is:
cup A