Chapter 3: Water and Life

Merged flashcards from Chapter 3 of Pearson's Campbell Biology, Twelfth Edition.

Buoyancy

The ability for solids to float on water if their overall density is lower; this includes ice, where water molecules become farther apart

Polar covalent bonds

Bonds created by the hydrogen atoms in water as a result of being attracted towards oxygen

Polar molecule

A molecule where the overall charge is unevenly distributed

• Water is an example of this it as it can form hydrogen bonds with other water molecules

Density

The measure of how much volume a certain amount of mass takes up

Water sustaining properties

Four properties aid an environment for life:

• Cohesive behavior

• Temperature moderation

• Expansion upon freezing

• Versatility as a solvent

Cohesion

Water molecules holding each other together through hydrogen bonds, creating high surface tension and aiding the transport of water and nutrients against gravity in plants

Surface tension

A measure of how difficult it is to stretch or break the surface of a liquid

Adhesion

An attraction of molecules between different substances; this occurs in between water and plant cell walls, countering the downward pull of gravity

Water temperature moderation

Water can absorb heat from warmer air and release stored heat to cooler air with only a slight change in its own temperature

Kinetic energy

The energy of motion

Thermal energy

The kinetic energy associated with random motion of atoms or molecules

Temperature

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

Heat

The thermal energy in transfer from one body of matter to another

Specific heat

The amount of heat that must be absorbed or lost for 1 gram of that substance to change its temperature by 1 degree centigrade

• Water’s is high, resisting temperature changes while absorbing heat energy

Coastal temperature regulation

Water can:

• Absorb and store a huge amount of heat from the sun in daytime and during summer while only warming up a few degrees

• Warm the air surrounding it due to gradual cooling at night and during winter

These enable temperature moderation in coastal areas

Evaporation

The transformation of a substance from liquid to gas

Evaporative cooling

The cooling of a surface as a liquid evaporates from it; this helps stabilize temperatures in organisms and bodies of water

Solution

A liquid that is a completely homogenous mixture of substances

Solvent

The dissolving agent of a solution

Solute

The substance that is dissolved in a solution

Aqueous solution

A solution where water acts as the solvent; this occurs often due to water’s polarity

Hydration shell

A sphere of water around each ion in an aqueous solution

Hydrophilic substances

Substances that have an affinity for water, like sugar and salts

• Most chemical reactions in organisms involve solutes dissolved in water

Hydrophobic substances

Substances that do not have an affinity for water, like oils

• This is because oils have relatively nonpolar bonds

Hydrogen bonds

Bonds between hydrogen atoms and oxygen atoms of different water molecules, creating hydrogen ions (protons) (H⁺) that result in one hydroxide ion (OH^-) and one hydronium ion (H₃O⁺)

Hydroxide

A water molecule that has lost a proton / hydrogen ion due to hydrogen bonding, represented as OH^-

Hydronium

A water molecule that has gained an extra proton / hydrogen ion due to hydrogen bonding, represented as H₃O⁺ or simply H⁺

Hydrogen ion

A shifting hydrogen atom between two water molecules in a hydrogen bond

pH scale

A measure between the concentrations of H⁺ and OH^- due to the presences of acids and bases

Acid

A substance that increases the H⁺ and reduces the OH^- concentration of a solution with a pH less than 7

Base

A substance that increases the OH^- and reduces the H⁺ concentration of a solution with a pH greater than 7

Buffer

Substances that minimize changes in the concentrations of H⁺ and OH^- of a solution to ensure pH levels closer to neutrality (7) using a weak acid and weak base

Ocean acidification

The formation of carbonic acid in seawater due to the presence of carbon dioxide, potentially harming underwater organisms by weakening shell development and coral formation by inhibiting calcification