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Wonderfully weird

What is water?

Water is a chemical compound; one of the most plentiful and essential of all the compounds in the world.

Chemical formula: H2O

Boiling point: 100°C

Freezing point: 0°C

Chemically speaking: Each molecule of water contains two atoms of hydrogen and one atom of oxygen. Much of the way water behaves has to do with the way the atoms are arranged inside the molecule.

Three physical states

Can you imagine casually coming across liquid oxygen or solid mercury? What makes water so interesting and unique is that it is the only known substance that can be found in solid, liquid and gaseous state within the Earth’s range of temperature and pressure.

Solid: The solid form of water is ice. Now, imagine a glass of water with ice cubes in it. Do the cubes float on top or sink to the bottom? They float because water is one of the few known substances whose solid form is less dense than the liquid. This means that, during winter, fish and other creatures can survive in the liquid water under the solid frozen ice on lakes and rivers.

Liquid: This form of water is the one we are probably most familiar with, and it can be found in this state at standard temperature and pressure. It is tasteless and odourless. It takes the shape of its container. What’s more, it is amphoteric, which means that it can act either as an acid or a base.

Gas: In its gaseous state, water is called water vapour. It is the invisible gas that is formed when water reaches its boiling point or evaporates. Though we can feel water vapour, we cannot see it.

Unusual properties

Water has an incredibly high boiling point and freezing point when compared to other compounds with a similar molecular structure. If not for this, water would boil or freeze very easily, making it difficult for organisms living in oceans and lakes to survive.

Only one liquid has a higher surface tension than water – mercury. This property explains why bubbles are round, small insects can walk on water, items that are heavier than water (such as a needle and a razor blade) can float on water if the conditions are right, and water drops are shaped the way they are.

Water is a solvent, which means that it allows other substances to dissolve in it. In fact, water dissolves more substances than any other solvent, giving it the name ‘universal solvent’.

Water has a high heat capacity, which means that it takes a lot of heat to change its temperature. This explains why, for example, the sand in the beach gets really hot on a summer’s day, while the water remains cool.

Fun facts

A drop of water contains over 1.5 sextillion molecules. A sextillion is 1 followed by 21 zeroes!

The oceans are teeming with life. A single drop of ocean water can contain millions of bacteria and viruses, protozoans, algae, plankton and so on.

Human adults are about 55 to 60% water, while newborn babies are about 78% water.

Water defies gravity when it moves upwards from the roots to the leaves of plants. This is called capillary action.

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Printable version | May 13, 2021 7:05:42 PM | https://www.thehindu.com/children/wonderfully-weird/article34132469.ece

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