- is a metabolite in many metabolic reactions
- has a relatively high specific heat capacity meaning it buffers temperature changes. Because the water molecules stick together it takes a lot of inputted energy to break them turning liquid water into a gas. This means it takes a lot of energy to heat a given mass of water meaning water can act as a buffer and resist temperature changes which is good for aquatic animals.
- has a relatively large latent heat of vapourisation. This means that a lot of energy is required to evaporate one kilogram of water. This means that evaporation is effective in cooling because a lot of the body's thermal energy goes into heating a small mass of perspiration (sweat) and the body doesn't lose much water.
- has strong cohesion between water molecules - it is a dipolar molecule made up of two atoms of hydrogen and one of oxygen. The O2 atom has a slightly negative charge whilst the H atoms have a slightly positive charge meaning a water molecule has both negative and positive poles. The negative pole of one water molecule is attracted to the positive pole of another forming a hydrogen bond. this causes water to stick together and have a cohesive nature. This supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air which provides habitats for organisms such as pond skaters.
Not on the spec but also useful to know, water:
- is a solvent, readily dissolving substances such as gases (O2 and CO2), wastes (ammonia and urea), inorganic ions and small hydrophilic molecules (amino acids, monosaccharides, ATP), and enzymes (whose reactions take place in solution)
- is not easily compressed so provides support e.g turgor pressure and the hydrostatic skeleton of animals
- is transparent meaning aquatic plants can photosynthesise and light rays can penetrate our lenses and the jelly-like fluid that fills eyes so light can reach the retina
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