Water is a neutral, colourless liquid which boils at 100 degrees Celsius and freezes at 0 degree Celsius.

It has an unusually high boiling point for a molecule of its relatively low molecular mass.

It has a greater specific heat capacity than almost any other liquid.

When water is electrolysed, 2 parts of hydrogen and 1 part of oxygen forms.

When an H-O bond is formed, slight amounts of (+)ve charges (known as delta positive changes) remain on the hydrogen. It attracts another oxygen from another water. Similarly, delta negative changes remain on the oxygen, which attracts hydrogen from another water molecule. Thus water has these unusual properties, including the one of cohesion and adhesion.

Pollution is a modification that takes place in our environment, water or air, caused by human influence suck as releasing substances into our water and air.

When water falls through the atmosphere, it dissolves harmful gases like nitrous oxide and sulfur dioxide from the polluted air. They react with water to form acidic compounds which result in acid rains. These rains destroy structures made up of metals like calcium. The water from acid rains can sweep into the ground, and could end up in ponds and lakes (could lead to an increased acidity of the water).

Nitrates and phosphates from excess fertilizers dissolve into the water and can end up in an enclosed lake/ pond. This can cause eutrophication (see later).

Metals compounds of Mercury and Cadmium from industrial waste can get dissolved in the water, if not disposed off properly. These compounds are highly toxic. However, it should be noted that some metal compounds are beneficial: calcium compounds in water help in a healthy growth of teeth.

Human waste from sewage can end up in water if not disposed off properly. Harmful organisms can encourage the spread of waterborne diseases.

Insoluble impurities such as plastic and oil can pollute water. Impurities like plastic can be detrimental to all the aquatic as well as human lives on this planet.