Water and Life

Flashcards covering key vocabulary terms related to water's properties, its role in life, solutions, and acid-base chemistry, based on the 'Water and Life' lecture notes.

Water

The only common substance to exist in the natural environment in all three physical states of matter, making life possible on Earth due to its unique emergent properties.

Polar molecule

A molecule like water, where the overall charge is unevenly distributed because electrons in polar covalent bonds spend more time near the oxygen than the hydrogen.

Hydrogen bonds

Interactions that form between polar water molecules, allowing them to connect with each other.

Cohesive behavior

One of water's four emergent properties that facilitate life, contributing to the transport of water and dissolved nutrients in plants.

Ability to moderate temperature

One of water's four emergent properties that facilitate life, allowing water to absorb or release large amounts of heat with only slight changes in its own temperature.

Expansion upon freezing

One of water's four emergent properties that facilitate life, causing ice to be less dense than liquid water and float.

Versatility as a solvent

One of water's four emergent properties that facilitate life, due to its polarity allowing it to dissolve many substances.

Surface tension

A measure of how difficult it is to break the surface of a liquid, unusually high for water due to hydrogen bonding.

Cohesion

The attraction between like molecules, contributing to the transport of water and dissolved nutrients against gravity in plants.

Adhesion

The attraction between different substances, such as between water and plant cell walls.

Kinetic energy

The energy of motion.

Thermal energy

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

Temperature

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

Heat

Thermal energy in transfer from one body of matter to another.

Calorie (cal)

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

Kilocalorie (kcal)

Equal to 1,000 calories, often seen as 'Calories' on food packages.

Joule (J)

Another unit of energy, where 1 J = 0.239 cal or 1 cal = 4.184 J.

Specific heat

The amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºC; water has a high specific heat.

Evaporation (or vaporization)

The transformation of a substance from liquid to gas.

Heat of vaporization

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

Evaporative cooling

The process by which the remaining surface of a liquid cools as it evaporates, helping stabilize temperatures in organisms and bodies of water.

Ice density

Water is less dense as a solid than as a liquid because hydrogen bonds keep the molecules further apart in a crystalline lattice at 0ºC.

Solution

A liquid that is a completely homogeneous mixture of substances.

Solvent

The dissolving agent of a solution.

Solute

The substance that is dissolved in a solution.

Aqueous solution

A solution in which water is the solvent.

Hydration shell

A sphere of water molecules that surrounds each ion when an ionic compound is dissolved in water.

Hydrophilic substance

A substance that has an affinity for water.

Hydrophobic substance

A substance that does not have an affinity for water, such as oil molecules due to their nonpolar bonds.

Molecular mass

The sum of the masses of all atoms in a molecule.

Mole (mol)

A unit of measurement for the number of molecules, where 1 mol = 6.02 × 10^23 molecules (Avogadro's number).

Molarity (M)

The number of moles of solute per liter of solution.

Hydrogen ion (H+)

A proton that is transferred from a hydrogen atom in a dissociated water molecule.

Hydroxide ion (OH–)

The molecule that lost a proton from a dissociated water molecule.

Hydronium ion (H3O+)

The molecule with an extra proton after water dissociation, often represented as H+.

Acid

A substance that increases the H+ concentration of a solution.

Base

A substance that reduces the H+ concentration of a solution.

Strong acids and bases

Substances that dissociate completely in water.

Weak acids and bases

Substances that reversibly release and accept back hydrogen ions, shifting the balance of H+ and OH–.

pH scale

A scale used by biologists to describe whether a solution is acidic or basic, defined by the negative logarithm of H+ concentration (pH = –log [H+]).

Acidic solutions

Solutions that have pH values less than 7.

Basic solutions

Solutions that have pH values greater than 7.

Neutral aqueous solution

An aqueous solution where [H+] is 10^-7, resulting in a pH of 7.

Buffers

Substances that minimize changes in concentrations of H+ and OH– in a solution, typically containing a weak acid and its corresponding base.

Ocean acidification

A process where CO2 absorbed by the oceans dissolves in seawater to form carbonic acid, threatening water quality due to human activities.