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Water Chemistry

Facts and Properties of Water

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Water is one of the most important molecules in chemistry.

Water is one of the most important molecules in chemistry, particularly biochemistry since water is essential for life.

John Foxx, Getty Images
Water is the most abundant molecule on the Earth's surface and one of the most important molecules to study in chemistry. Here's a look at some facts about water chemistry.

What Is Water?

Water is a chemical compound. Each molecule of water, H2O or HOH, consists of two atoms of hydrogen bonded to one atom of oxygen.

Water Facts

  • Other names for water are: dihydrogen monoxide, oxidane, hydroxylic acid, and hydrogen hydroxide

  • molecular formula of water: H2O

  • molar mass of water: 18.01528(33) g/mol

  • density 1000 kg/m3, liquid (4 °C) or 917 kg/m3, solid. This is why ice floats on water.

  • melting point: 0 °C, 32 °F (273.15 K)

  • boiling point: 100 °C, 212 °F (373.15 K)

  • acidity (pKa): 15.74

  • basicity (pKb): 15.74

  • refractive index: (nD) 1.3330

  • viscosity: 0.001 Pa s at 20 °C

  • crystal structure: hexagonal

  • molecular shape: bent

  • Pure liquid water at room temperature is odorless, tastless and nearly colorless. Water has a faint blue color, which becomes more apparent in large volumes of water.

  • Water has the second highest specific enthalpy of fusion of all substance (after ammonia). The specific enthalpy of fusion of water is 333.55 kJ·kg−1 at 0 °C.

  • Water has the second highest specific heat capacity of all known substances. (Ammonia has theh highest specific heat.) Water also has a high heat of vaporization (40.65 kJ·mol−1). The high specific heat and heat of vaporization result from the high degree of hydrogen bonding between water molecules. One consequence of this is that water is not subject to rapid temperature fluctuations. On Earth, this helps to prevent dramatic climate changes.
Test your knowledge with a water trivia quiz.
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