Ch. 3 - Water and Life

What makes water unique among substances in the natural environment?

Only common substance that exists in all three physical states of matter: solid, liquid, and gas.

What are the emergent properties of water that contribute to Earth's suitability for life?

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

How does the structure of a water molecule contribute to its properties?

The polar covalent bonds in water molecules result in uneven charge distribution, allowing for hydrogen bonding.

What is cohesion in the context of water molecules?

Refers to the attraction between water molecules, which contributes to surface tension and the transport of water in plants.

What is adhesion in relation to water?

Attraction between water and different substances, such as plant cell walls, helping counteract gravity.

How does water moderate temperature?

Absorbs heat from warmer air and releases it to cooler air, allowing it to absorb or release a large amount of heat with minimal temperature change.

What is the specific heat of water?

The specific heat of water is 1 cal/(g · °C), meaning it resists temperature changes.

What is evaporative cooling?

Process where the evaporation of water cools the remaining liquid, helping to stabilize temperatures in organisms.

Why does ice float on liquid water?

Less dense than liquid water due to the crystalline structure formed by hydrogen bonds, making it about 10% less dense.

What is a solution in chemistry?

Homogeneous mixture of substances, where the solvent is the dissolving agent and the solute is the substance being dissolved.

Why is water considered a versatile solvent?

Water's polarity allows it to dissolve many ionic and polar substances, including large polar molecules like proteins.

What defines a hydrophilic substance?

A substance that has an affinity for water.

What defines a hydrophobic substance?

A substance does not have an affinity for water, typically because it contains nonpolar bonds.

What is molarity in the context of solutions?

The number of moles of solute per liter of solution.

What is the significance of Avogadro's number?

Defines the number of molecules in one mole of a substance.

What happens to hydrogen ions (H+) and hydroxide ions (OH-) in water?

In pure water, the concentrations of H+ and OH- are equal; however, adding acids or bases alters these concentrations.

What is an acid?

Substance that increases the H+ concentration in a solution.

What is a base?

Substance that reduces the H+ concentration in a solution.

What is the pH scale?

Measures the acidity or basicity of a solution, with values less than 7 being acidic, greater than 7 being basic, and 7 being neutral.

What is the role of buffers in biological systems?

Minimize changes in H+ and OH- concentrations in a solution, helping maintain a stable pH.

What is ocean acidification?

Occurs when CO2 from human activities dissolves in seawater, forming carbonic acid and lowering the pH of the ocean.

How does water's high specific heat benefit life?

It minimizes temperature fluctuations, allowing for stable environments that support life.

What is the heat of vaporization?

The amount of heat a liquid must absorb for 1 g to be converted to gas.

What is the significance of water's density at different temperatures?

Water reaches its greatest density at 4ºC, and if ice sank, it would lead to the freezing of bodies of water, making life impossible.

What is thermal energy?

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

What is the relationship between temperature and kinetic energy?

Temperature is a measure of the average kinetic energy of the molecules in a body of matter.