Properties of Water

Life would not have existed on earth without water. Water molecules are composed of one oxygen atom and two hydrogen atoms. Together, the hydrogen and oxygen molecules form a shape that resembles the head of Mickey Mouse. 

While water molecules seem to be simple compounds, their properties have profound impact on life. Because of the arrangement of hydrogen and oxygen atoms, water molecules have polarized charges (one end is positive and the other end is negative). Due to their polarized nature, 2 adjacent water molecules can form a linkage via a hydrogen bond.

The polarized nature of water causes other molecules to be either hydrophilic (like water) or hydrophobic (afraid of water). This property allows certain molecules to dissolve in water while preventing others from entering the cell. For example, hydrophobic interaction can hold molecules together.

Osmosis

Another important property of water is its ability to facilitate the transfer of molecules through osmosis. When 2 aqueous solutions are separated by a membrane that only allows the passage of water molecules, water will move from the less concentrated to the more concentrated side (Shown in the diagram below).

Hydrophobic interactions can hold molecules together: 2 or more hydrophobic groups surrounded by water will tend to coalesce since they thereby cause less disruption to the hydrogen-bonded structure of water (Shown in the diagram below. Red hexagons represent hydrophobic material and blue dots represent water molecules.).

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