Water and Life - Biology 11A

Flashcards covering key vocabulary terms and concepts from Chapter 2.2 Water and Life lecture notes.

Hydrogen Bond

A weak bond between a partially positive hydrogen atom (covalently bonded to a more electronegative atom like O, N, or S) and another electronegative atom (O, N, or S).

Polar Molecule

A molecule with unequal distribution of charge, such as water, where oxygen has a partial negative charge ($\delta^-$) and hydrogen has a partial positive charge ($\delta^+$).

Emergent Properties of Water

The four properties of water that contribute to Earth's suitability for life: water is the solvent of life, ice floats on water, moderation of temperature by water, and cohesion and adhesion of water molecules.

Hydrophilic

Refers to water-loving substances, such as polar molecules and salts, that readily dissolve in water.

Hydrophobic

Refers to water-fearing substances, such as nonpolar molecules and fats with long nonpolar C-H chains, that do not dissolve in water.

Specific Heat Capacity

The amount of heat required to raise $1\,\text{g}$ of a substance by $1\,^\circ\text{C}$. Water has a high specific heat capacity, requiring more energy to raise its temperature.

Heat of Vaporization

The amount of heat required for $1\,\text{g}$ of a liquid to convert to a gas. For water at $25\,^\circ\text{C}$, this is about $580\,\text{cal}$ of heat.

Evaporative Cooling

The reduction in temperature of a surface left behind as a liquid evaporates.

Cohesion

The phenomenon where water molecules form hydrogen bonds with each other (the same substance).

Adhesion

The attraction where water molecules form hydrogen bonds with other, unlike molecules or surfaces, such as xylem vessel walls.

Surface Tension

A property related to cohesive dipole intermolecular forces that allows the surface of water to resist external forces, enabling organisms like water striders to stay afloat.

Gerris sp.

The genus of water strider whose ability to stay afloat is facilitated by the cohesive and adhesive properties of water.

pH Scale

A measure of hydrogen ion concentration in a solution, calculated as $\text{pH} = -\log_{10}[\text{H}^+]$.

Ion Product of Water

The equilibrium relationship in aqueous solution where the product of hydrogen ions and hydroxide ions equals $10^{-14}$, written as $[\text{H}^+][\text{OH}^-] = 10^{-14}$.

Strong Acid

An acid, such as $\text{HCl}$, that completely dissociates into hydrogen ions ($\text{H}^+$) and chloride ions ($\text{Cl}^-$) in solution.

Weak Acid

An acid, such as carbonic acid ($\text{H}_2\text{CO}_3$), that reversibly dissociates into hydrogen ions ($\text{H}^+$) and its conjugate base ($\text{HCO}_3^-$).

Buffer

A solution of a weak acid and its corresponding base that stabilizes pH by binding excess hydrogen ions when an acid is added or releasing hydrogen ions when a base is added.

Carbonic Acid (H2CO3)

A weak acid in human blood that acts as a buffer system ($\text{H}_2\text{CO}_3 \rightleftharpoons \text{HCO}_3^- + \text{H}^+$) to prevent extreme changes in blood pH.