Tag: Diffusion

A matter is any substance that has mass and occupies space. There are three states of matter: solid, liquid and gas. Most of the matters can exist in all three states.

Diffusion is the net movement of molecules or ions from where they are in a higher concentration to where they are in a lower concentration i.e. down a concentration gradient.

Cells need food materials which they can oxidise for energy or use to build up their cell structures. They also need salts and water, which play a part in chemical reactions in the cell. Finally, they need to get rid of substances such as carbon dioxide, which, if they accumulated in the cell, would upset some of the chemical reactions or even poison the cell. Substances may pass through the cell membrane either passively by diffusion or actively by some form of active transport.