Water (H2O) is the most abundant compound on Earth's surface, covering 70 percent of the planet. In nature, water exists in liquid, solid, and gaseous states. It is in
dynamic equilibrium between the liquid and gas states at standard temperature and pressure. At room temperature, it is a tasteless and odorless liquid, nearly colorless
with a hint of blue. Many substances dissolve in water and it is commonly referred to as the universal solvent. Because of this, water in nature and in use is rarely pure and
some properties may vary from those of the pure substance. However, there are also many compounds that are essentially, if not completely, insoluble in water.
the only common substance found naturally in all three common states of matter and it is essential for all life on Earth. Water makes up 55% to 78% of the human body.
One of the things that makes our planet special is the presence of liquid water. Water is fundamental for all life; without it every living thing would die. It covers about 70% of
Earth's surface and it makes up 65-75% of our bodies (82% of our blood is water). Even though water seems boring no color, taste, or smell it has amazing properties that
make it necessary for supporting life. The chemical composition of water is H2O . two hydrogen atoms and one oxygen atom. Water has special properties because of the
way these atoms bond together to form a water molecule, and the way the molecules interact with each other. When the two hydrogen atoms bond with the oxygen, they
attach to the top of the molecule rather like Mickey Mouse ears. This molecular structure gives the water molecule polarity, or a lopsided electrical charge that attracts other
atoms. The end of the molecule with the two hydrogen atoms is positively charged. The other end, with the oxygen, is negatively charged. Just like in a magnet, where north
poles are attracted to south poles ('opposites attract'), the positive end of the water molecule will connect with the negative end of other molecules. What does this mean for
us? Water's polarity allows it to dissolve other polar substances very easily. When a polar substance is put in water, the positive ends of its molecules are attracted to the
negative ends of the water molecules, and vice versa. The attractions cause the molecules of the new substance to be mixed uniformly with the water molecules. Water
dissolves more substances than any other liquid - even the strongest acid! Because of this, it is often called the 'universal solvent.'
The dissolving power of water is very
important for life on Earth. Wherever water goes, it carries dissolved chemicals, minerals, and nutrients that are used to support living things. Because of their polarity, water
molecules are strongly attracted to one another, which gives water a high surface tension. The molecules at the surface of the water "stick together" to form a type of 'skin'
on the water, strong enough to support very light objects. Insects that walk on water are taking advantage of this surface tension. Surface tension causes water to clump in
drops rather than spreading out in a thin layer. It also allows water to move through plant roots and stems and the smallest blood vessels in your body as one molecule
moves up the tree root or through the capillary, it 'pulls' the others with it. Water is the only natural substance that can exist in all three states of matter solid, liquid, and
gas - at the temperatures normally found on Earth. Many other substances have to be super-heated or -cooled to change states. The gaseous state of water is present
continually in our atmosphere as water vapor. The liquid state is found everywhere in rivers, lakes, and oceans. The solid state of water, ice, is unique. Most liquids contract
as they are cooled, because the molecules move slower and have less energy to resist attraction to each other. When they freeze into solids they form tightly-packed
crystals that are much denser than the liquid was originally. Water doesn't act this way. When it freezes, it expands: the molecules line up to form a very 'open' crystalline
structure that is less dense than liquid water.
A healthy sedentary adult living in a temperate climate should drink 1.5 litres of water per day. This threshold of drinking water enables to balance water losses and keep
one’s body properly hydrated. Water is a major constituent of our bodies and vital organs. It provides five vital functions in our body:
-Water is a carrier, distributing essential nutrients to cells, such as minerals, vitamins and glucose.
-Water removes waste products including toxins that the organs’ cells reject, and removes them through urines and faeces.
-Water participates in the biochemical break-down of what we eat.
-Water has a large heat capacity which helps limit changes in body temperature in a warm or a cold environment. Water allows the body to release heat when ambient
temperature is higher than body temperature. The body begins to sweat, and the evaporation of water from the skin surface very efficiently cools the body.
-Water is an effective lubricant around joints. It also acts as a shock absorber for eyes, brain, spinal cord and even for the foetus through amniotic fluid.
-Water is at the center of life. This is why nobody can live more than 3 to 5 days without any water intake.