Is water a solid, a liquid or a gas?

As always with these kinds of questions the first consideration is "at what temperature" ? We are familiar with water being seen as a solid (below 0° C) which we call ice, a liquid between 0° C and 100° C, and a gas above 100° C which we call steam - all temperatures assuming that we are talking about 1 atmosphere pressure.

This is because water is a simple molecular substance with strong covalent bonds between the hydrogen and oxygen atoms, but only relatively weak intermolecular forces between molecules which do not take much energy to break, so water has a low melting point and boiling point.

We generally don't consider liquids to have much space between the particles so they are non-compressible, but the particles can move around each other.

Solid water (ice) is unusual in that it is less dense than liquid water - that is why ice cubes float in a drink because ice is less dense than liquid water. This is because the intermolecular forces between water molecules are really quite unusual, and at A level we would talk about this is much more detail. Water molecules can form hydrogen bonds, a particular type of intermolecular force which have a huge impact on all sorts of properties on this planet, with particular implications for biological chemistry.

Water is a liquid as it is free flowing and the particles of water have a space between them therefore water is a liquid