Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Water molecules are polar, with partial positive charges () on the hydrogen atoms and a partial negative charge () on the oxygen atom due to the unequal sharing of electrons in the covalent bonds.
Hydrogen bonding occurs when the hydrogen of one molecule is attracted to the oxygen of another. This intermolecular force is responsible for most of water's unique properties.
Cohesion is the attraction between water molecules. This allows for high surface tension, enabling organisms like pond skaters to walk on water.
Adhesion is the attraction between water molecules and other polar surfaces. This is critical for capillary action in the xylem of plants, allowing water to move against gravity.
Thermal properties: Water has a high specific heat capacity (), meaning it can absorb or lose significant heat with little temperature change, providing stable aquatic habitats.
Cooling effect: Water has a high latent heat of vaporization. To evaporate, must break hydrogen bonds, absorbing heat from the surface (e.g., sweat cooling the skin).
Solvent properties: Water is the 'universal solvent' for polar and ionic substances. It forms hydration shells around ions like and .
Metabolism: Water is used in hydrolysis reactions to break down polymers and is a product of condensation reactions that build polymers.
📐Formulae
💡Examples
Problem 1:
Compare the physical properties of water () and methane () in the context of molecular bonding.
Solution:
has a boiling point of and a specific heat capacity of . has a boiling point of and a specific heat capacity of .
Explanation:
Water is polar and forms hydrogen bonds, which require significant energy to break. Methane is non-polar and only exhibits weak London dispersion forces, leading to much lower boiling and melting points despite having a similar molecular mass to water.
Problem 2:
Explain how the solubility of glucose and lipids in water affects their transport in human blood.
Solution:
Glucose is polar and dissolves directly in blood plasma. Lipids are non-polar () and must be transported inside lipoproteins.
Explanation:
Because is a polar solvent, it can only dissolve substances that can form hydrogen bonds or have charges (). Non-polar substances like fats cannot disrupt the hydrogen bonds of water and are excluded, necessitating specialized transport mechanisms like chylomicrons.