When Water Wows: The Fascinating Properties of H2O

Water is one of the most ubiquitous substances on Earth. It covers 71% of the Earth’s surface and is essential for all forms of life. But water is more than just a life-supporting liquid. It has a variety of physical and chemical properties that make it fascinating and unique.

The Molecular Structure of Water

Water is a compound made up of two hydrogen atoms and one oxygen atom, which makes its chemical formula H2O. These atoms are joined together through the sharing of electrons to form a bent, V-shaped molecule. The oxygen atom is located at the center of the molecule and attracts electrons more strongly than the two hydrogen atoms. Therefore, the oxygen end of the molecule has a partial negative charge while the hydrogen end has a partial positive charge.

The Role of Hydrogen Bonds

One of the most important properties of water is the fact that its molecule can form hydrogen bonds. These bonds are formed due to the attraction between the partially negative oxygen end of one water molecule and the partially positive hydrogen end of another water molecule. This attraction results in clusters of water molecules held together by weak hydrogen bonds.

  • Hydrogen bonds are responsible for many of water’s unique properties, such as its high surface tension, its high boiling and melting points, and its ability to dissolve many substances.
  • In addition, hydrogen bonds are also believed to play a key role in the structure of biological molecules such as proteins and DNA.

The Physical Properties of Water

Density and Compressibility

Water is denser than air, which means it has more mass per unit of volume. The density of water is also affected by temperature and pressure. When water is cooled, it becomes denser until it reaches its maximum density at 4°C. Below this temperature, water becomes less dense as it freezes into ice.

Water is also a relatively incompressible liquid. This means that it is very difficult to compress water into a smaller volume. The compressibility of water is influenced by temperature and pressure, with colder and deeper water being less compressible than warmer and shallower water.

Boiling and Freezing Points

Water has a high boiling point (100°C) and a high melting point (0°C). This is due to the many hydrogen bonds that hold water molecules together. These bonds require a lot of energy to break, which is why it takes a lot of heat to boil water or to melt ice.

Surface Tension and Adhesion/Cohesion

Water has a high surface tension, which means that its surface behaves like a thin elastic skin. This surface tension results from hydrogen bonds between water molecules at the surface. This property is responsible for the curved shape of water droplets and the ability of certain insects to walk on water.

Water also exhibits strong adhesion and cohesion forces. Adhesion refers to the attraction between water molecules and other substances, while cohesion refers to the attraction between water molecules. These forces are responsible for the ability of water to wet surfaces, to form menisci in tubes and pipettes, and to form droplets on surfaces.

The Chemical Properties of Water

Dissolving Power

Water is often called the universal solvent because it has the ability to dissolve a wide variety of substances. This is due to the polar nature of the water molecule, which allows it to interact with polar and charged molecules. When a solute dissolves in water, the water molecules surround and separate each ion or molecule, breaking apart ionic or covalent bonds.

The ability of water to dissolve different substances is influenced by temperature, pressure, and the concentration of solute particles in solution. For example, as the concentration of salt in water increases, the solubility of the salt decreases.

pH and Acidity

Water is a neutral substance with a pH of 7. However, when certain substances dissolve in water, they release hydrogen ions (H+) or hydroxide ions (OH-), which can change the pH of the solution. Substances that release hydrogen ions are called acids, while substances that release hydroxide ions are called bases.

The pH of a solution is a measure of its acidity or basicity. Solutions with a pH below 7 are acidic, while solutions with a pH above 7 are basic. The pH scale is logarithmic, which means that each unit change in pH represents a 10-fold change in acidity. For example, a solution with a pH of 2 is 100 times more acidic than a solution with a pH of 4.


Water is an amazing substance with a range of unique properties that make it essential for life as we know it. From its molecular structure and the role of hydrogen bonds to its physical and chemical properties, water never ceases to amaze. Whether you’re a scientist or just someone interested in the natural world, there’s always something new to learn about the fascinating properties of H2O.

Common Water Questions

  • What is water’s chemical formula?
  • What is the role of hydrogen bonds in water?
  • What is the density of water?
  • What is water’s boiling and freezing point?
  • What is the meaning of water’s high surface tension?
  • What is water’s ability to dissolve a wide variety of substances called?
  • What is the pH of water?
  • What is the pH of an acidic solution?


1. Martin Chaplin. 2018. Water Structure and Science. https://www1.lsbu.ac.uk/water/
2. P.W. Atkins, Julio de Paula. Physical Chemistry: Thermodynamics, Structure, and Change. Oxford University Press, 2014.
3. C. Michael Hogan. 2009. Density. Encyclopedia of Earth. https://www.eoearth.org/article/Density

4. John W. Moore, Conrad L. Stanitski, Peter C. Jurs. Chemistry: The Molecular Science, 5th Edition. Cengage Learning, 2013.

5. John D. Ferry. Viscoelastic Properties of Polymers, 3rd Edition. John Wiley & Sons, 1980.
6. David L. Nelson, Michael M. Cox. Principles of Biochemistry, 5th Edition. W.H. Freeman and Company, 2008.

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