Water is the most common substance on the planet yet it has some very unusual characteristics. Pure water is odourless and tasteless. Water has a very simple atomic structure; water is composed of two elements, hydrogen and oxygen- making it a compound.
Pure water has a neutral pH of 7, which is neither acidic or basic/alkaline. One of the most remarkable things about water is that it can be found in all three states of matter: solid ice, liquid water and gaseous water vapour (steam). When water is cooled to about OºC it will freeze. When water is heated to about 100ºC it boils, changing from a liquid to vapour. Earth’s water is constantly interacting, changing from one state to the next and is in constant motion. This perhaps makes water one of the greatest examples of recycling.
Did you know that water expands (becomes less dense) by 9% when it freezes? This is very unusual for liquids. Think of the ice blocks in your glass of water on a hot summer’s day- they float and do not sink. This is one of the wonderfully unusual characteristics of water which is very helpful in Nature. An example being a frozen lake- ice forms on the surface but the water beneath remains liquid. This helps aquatic organisms survive through cold winters.
Another remarkable characteristic of water is that it has the capability to dissolve many things. This means that wherever water flows, either through the ground or through our bodies, it picks up valuable chemicals, minerals and nutrients. This is the reason why pure water is rare in Nature. Even rainwater, the purest natural water water, contains chemicals dissolved from the air.
Minerals dissolved in water help nourish living organisms. Harmful substances, such as those from decaying animal and vegetable matter and poisonous chemicals, may also be dissolved in water – a good reason to have drinking water tested. Water, being such a good solvent, is also perfect for washing.
Water has a high specific heat index- this means that water can absorb a substantial amount of heat before it begins to heat up. This property makes water very important to many industries and mundane things like your car’s radiator. The high specific heat index of water also helps regulate the rate at which air temperature changes. This is why temperature change between seasons is gradual rather than sudden, especially near oceans.
Another interesting characteristic of water is that it has a high surface tension. This results in the water being ‘sticky’ and elastic and tends to clump together in drops rather than spreading out in a thin film. This surface tension is also responsible for capillary action which allows water (and its dissolved substances) to move through the roots of plants and blood vessels in our bodies. A practical demonstration of this property can be observed when a straw is placed in a glass of water. The water ‘climbs’ up the straw- when one water molecule is attracted to a straw molecule, the other water molecules which are cohesively attracted to that water molecule, also move up into the straw. Capillary action is limited by gravity and the diameter of the vessel, in this case a straw. The thinner the straw, the higher the water will be moved by capillary action. This property has its uses both in Nature and in industry.
Source: The Water Wheel November/December 2009 Volume 8 No 6
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