Here's why:

* Colloids: These are mixtures where one substance is dispersed evenly throughout another, but the particles are larger than those found in a solution. The dispersed particles are too small to be seen with the naked eye but are large enough to scatter light. Examples include milk, fog, and blood.

* Suspensions: These are mixtures where particles are larger than those in a colloid, and they settle out over time. Examples include sand in water, or chalk in water.

Pure water is a solution because it consists of water molecules (H2O) dissolved in other water molecules. The molecules are evenly distributed and don't settle out.

However, water can act as a solvent for other substances, which can form colloids or suspensions depending on the size of the dispersed particles:

* Colloid: Milk is an example of a colloid where tiny fat globules are dispersed in water.

* Suspension: Muddy water is an example of a suspension where soil particles are suspended in water.

Let me know if you have any other questions!