Point 1 of 8 — The Molecular Structure of Water, Its Unique Properties and Water SustainabilityQuestion bank: 0 questions (0 with pictures)
01Scientific terms
Polar molecule: a molecule with a partial negative charge on one side and a partial positive charge on the other, as in H₂O.
Hydrogen bond: the weak electrostatic attraction between a hydrogen atom covalently bonded to O, N or F and a lone pair on another electronegative atom.
Cohesion: attraction between like molecules (water–water); adhesion is attraction between unlike surfaces (water–glass).
Surface tension: the energy needed to increase the surface area of a liquid by one unit; it is the result of cohesion at the surface.
Capillarity: the rise or fall of a liquid in a narrow tube caused by adhesion to the walls together with cohesion within the liquid.
Hardness: the dissolved calcium and magnesium salts in water; temporaryhardness is due to bicarbonates, permanenthardness to sulfates and chlorides.
Dissolved oxygen (DO): the amount of O₂ free in water, typically 4–14 mg/L; it indicates the health of an aquatic ecosystem.
Biological oxygen demand (BOD): the oxygen needed by micro-organisms to decompose the organic matter in a volume of water; high BOD means pollution.
Virtual water: the water embedded in a produced commodity — 1 kg of wheat needs about 1,000–1,500 L of water.
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