Water and Life — Lecture Notes Review

A comprehensive set of practice flashcards covering water properties, thermodynamics, solutions, acids/bases, pH, and buffers as described in the notes.

What type of bonds in water molecules lead to hydrogen bonding and polarity?

Polar covalent bonds cause an uneven distribution of charge; electrons spend more time near oxygen, enabling hydrogen bonds between water molecules.

List the four emergent properties of water that support life.

Cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent.

What is cohesion in water, and what does it cause?

Hydrogen bonds hold water molecules together; cohesion leads to high surface tension and helps transport water in plants.

What is adhesion?

Attraction between water and other substances (e.g., plant cell walls), helping counter gravity.

How does water moderate temperature in the environment?

Water absorbs heat from warm air and releases stored heat to cooler air, due to its high specific heat.

Define thermal energy.

The kinetic energy associated with the random motion of atoms or molecules.

Define temperature.

The average kinetic energy of the molecules in a body of matter.

What is a calorie (cal)?

The amount of heat required to raise the temperature of 1 g of water by 1°C, or the heat released when 1 g of water cools by 1°C.

What does kilocalorie (kcal) mean on food labels?

1 kcal equals 1,000 cal; Calories on food labels are kilocalories.

What is a joule (J)?

A unit of energy; 1 J = 0.239 cal, and 1 cal = 4.184 J.

Why does water have a high specific heat?

Hydrogen bonding: heat is absorbed to break bonds and released as bonds form, stabilizing temperature.

What is heat of vaporization?

The amount of heat required to convert 1 g of liquid water to gas.

What is evaporative cooling?

As a liquid evaporates, its surface cools, helping stabilize temperatures in organisms and bodies of water.

Why is ice less dense than liquid water?

In ice, hydrogen bonds form a lattice that keeps molecules farther apart, making ice ~10% less dense than liquid water; water is densest at 4°C.

Why is it important that ice floats on water?

If ice sank, bodies of water could freeze solid, making life impossible; floating ice insulates aquatic environments.

What is a solution?

A completely homogeneous mixture of substances; the solvent dissolves the solute.

What is an aqueous solution?

A solution where water is the solvent.

What is a hydration shell?

A sphere of water molecules around each dissolved ion in solution.

What is hydrophilic vs hydrophobic?

Hydrophilic substances have an affinity for water; hydrophobic substances do not (e.g., oils).

What is solute concentration in solutions (definition of molarity)?

Molarity (M) is the number of moles of solute per liter of solution.

What is molecular mass and why is it important?

Sum of the masses of all atoms in a molecule (molar mass); used to calculate amounts of substances in moles.

What is Avogadro’s number?

6.02 × 10^23 molecules per mole; relates to daltons and grams in measurements.

What is a dalton?

A unit of atomic/molecular mass; defined so that 6.02 × 10^23 daltons equal 1 gram.

What ispH?

The negative logarithm of H+ concentration; describes how acidic or basic a solution is.

What is the autoionization of water and its key relation?

Water dissociates into H+ and OH−; [H+][OH−] = 1.0 × 10^−14 at 25°C; pH = −log[H+].

What is an acid and what is a base in biology?

An acid increases H+ concentration; a base decreases H+ concentration in solution.

What is the typical pH range for most biological fluids?

Approximately 6 to 8.

What is a buffer and how does it work?

A substance (often a weak acid and its conjugate base) that minimizes changes in pH by reversibly binding or releasing H+.

What is the neutral pH value at 25°C, and what are [H+] and [OH−]?

pH 7; [H+] = [OH−] = 1.0 × 10^−7 M.