Because water is a polar molecule this allows it to "hook up" with other molecules, including itself. Water molecules can form hydrogen bonds, which give shape to water as a whole. One single water molecule can form bonds with four other water molecules, and these bonds aren't that strong, the fact that water can form so many of them gives water its "sticky" nature.
The ability of water molecules to quickly break and re-form hydrogen bonds gives it a property called cohesion. Water's high amount of cohesion makes it "sticky" such that across the air-water area, a kind of "water barrier" is set up that allows things to float easier on the surface and causes water to form beads.
More substances dissolve in water than in any other liquid. The reason why water is so good at dissolving is because of its capability relates to its polarity; water offers positive and negative charges to which other atoms of molecules can attach.
Water has the highest heat capacity of any liquid or solid, except ammonia. The heat capacity of a substance is defined as the amount of heat that is required to raise the temperature of 1 gram of a substance by 1 degree. The amount of heat for water is defined as 1 calorie. This means that the heat capacity of all other substances is lower, i.e. that it takes less than 1 calorie to raise the temperature of 1 gram of the substance by 1 degree.
Water is essential to life as it is used everywhere constantly. Water is used for transport. Plants uptake minerals which are found in water through their roots. Transpiration stream and water based movement of sugars and amino acids, hormones etc. in phloem occurs in solution.
All transport fluids used in animals such as cytoplasm, blood, plasma and tissue fluid are water-based. Many essential metabolites dissolve completely into water such as glucose, amino acids, vitamins and minerals.
The transpiration stream is held together by cohesion (the process by which water molecules hydrogen bond to other water molecules) and adhesion (water molecules bind to side of xylem vessel ). Such forces also give rise to capillary in tubes of very small diameter. The low viscosity of water enables it to flow easily through tubes.
Water is needed in chemical reactions. The combination of thermal stability and excellent solvent properties make water an ideal environment for chemical reactions to take place. All enzyme reactions of photosynthesis, respiration, excretion etc. occurs in water.
Water is used for temperature control. The high specific heat capacity allows water to act as a buffer, essential in endothermic organisms that need to maintain a constant body temperature in order to stay in enzyme activity and thereby regulate metabolism.
The high incidence of hydrogen bonds makes it difficult for water molecules to evaporate, when they do so much energy is released and this is involved in cooling mechanisms. Water remains a liquid over a huge temperature range- essential for metabolism and useful in aquatic organisms which avoid freezing.
In some creatures water is used to cool them down. The body of the creature produces a solution called sweat which is released from the sweat glands in the skin covering the places which are hot and thus calling them down.
Water is used for support. In plants cells water confers turgidity. This is essential for maintaining maximum leaf surface area allowing light absorption and photosynthesis. As well as maintaining aerial parts of the plant to maximise speed dispersal or pollination.
In animals, water- filled tissues also contribute to skeletal support. In organisms which possess a hydrostatic skeleton, water is the major component of the fluid in the coelom against which muscles can act. For aquatic organisms water provides support through buoyancy.
Water is used for movement. Nastic movements which depend upon the osmotic flow of water in the tissues. A good example of this movement is the opening and closing of the carnivorous flower the Venus Fly Trap.
Also organisms such as the earthworm and leeches use their hydrostatic skeletons to move around.
Lastly water is used in reproduction. Organism which employ sexual reproduction use water to bring the male and female gametes together in the process of fertilisation. In mammals the foetus develops in a water filled sac which provides physical and thermal stability. Many mammals reproduce using sperm. Sperm swims and needs a solution to swim in. Without water the sperm would be unable to reach the ovaries and fertilise the egg.
Water is used in many ways and without it their would be no life.
