A1.1 Water - TeachMe Study Notes

Comprehensive vocabulary flashcards covering the chemical structure, unique physical properties, biological significance, evolutionary role, and aquatic organism adaptations of water from Topic A1.1.

Water Composition

A molecule composed of one oxygen ($O$) atom and two hydrogen ($H$) atoms joined by covalent bonds, giving it the chemical formula $H_2O$.

Electronegativity

A measure of how "greedy" an atom is for electrons; oxygen is more electronegative than hydrogen, pulling shared electrons closer in covalent bonds.

Polar Molecule

A molecule with an unequal distribution of charge, resulting in one side being more negative ($\delta-$) and the other side being more positive ($\delta+$).

Hydrogen Bond

An intermolecular attraction between the partially positive ($\delta+$) hydrogen atom of one water molecule and the partially negative ($\delta-$) oxygen atom of another water molecule.

Hydrogen Bonding Capacity of Water

A single water molecule can form a total of $4$ hydrogen bonds, which continually break, reform, and move around in the liquid state.

Cohesion

The attraction between molecules of the same type, such as water molecules binding to each other via hydrogen bonds.

Adhesion

The attraction between unlike molecules, allowing polar water molecules to stick to other polar or charged substances.

Surface Tension

The resistance of a liquid's surface to being broken, caused by surface water molecules experiencing a net inward attraction because there are no water molecules above them.

Concave Meniscus

A curved water surface that forms in glass tubes because adhesion between water and glass is stronger than cohesion ($\text{Adhesion} > \text{Cohesion}$), causing water to climb slightly up the walls.

Convex Meniscus

A curved surface formed by mercury ($Hg$) because cohesion between its atoms is stronger than adhesion to glass ($\text{Cohesion} > \text{Adhesion}$), causing it to pull away from the walls.

Capillary Action

The movement of a liquid up a narrow tube or through tiny spaces caused by the combined effects of cohesion and adhesion.

Transpiration Pull

The main force responsible for transporting water upward through xylem vessels in tall plants.

Solute

The substance that is dissolved in a solvent.

Solvent

The substance that dissolves other substances (solutes).

Solution

A homogeneous mixture formed when a solute has been dissolved by a solvent.

Dissolving

The process where partially charged ends of water molecules surround ions and polar molecules, pulling them apart and dispersing them throughout the water.

Universal Solvent

A description of water reflecting its ability to dissolve more substances than most liquids, specifically ionic and polar substances, though not non-polar oils and fats.

Hydrophilic

"Water loving"; describes polar substances and ions (such as $Na^+$, $K^+$, $Cl^-$, glucose, and urea) that readily dissolve in and interact with water.

Hydrophobic

"Water fearing"; describes non-polar substances (such as triglycerides, fatty acids, cholesterol, $O_2$, and $CO_2$) that cannot form favorable attractions with water and do not dissolve.

Condensation Reaction

A biochemical reaction that joins molecules together and produces water as a product.

Hydrolysis Reaction

A chemical reaction that breaks molecular bonds by using water as a reactant.

Waxy Cuticle

A non-polar layer located predominantly on the top of leaves that acts as a barrier to reduce water loss via evaporation.

Specific Heat Capacity

The amount of heat energy required to raise the temperature of $1\,\text{kg}$ (or $\text{g}$) of water by $1\,^\circ\text{C}$.

Thermal Conductivity

The ability of a substance to transfer heat; water transfers heat much faster than air because its molecules are held closely together by hydrogen bonds.

Viscosity

The resistance a fluid exerts against an object moving through it, which in water requires breaking hydrogen bonds so molecules can slide past each other.

Buoyancy

An upward force exerted on an object placed in a medium, equal to the weight of the medium pushed aside (displaced) by the object.

Blubber

A thick subcutaneous layer of fat found in organisms like the Ringed seal (Pusa hispida) that provides thermal insulation and increases buoyancy because it is less dense than water.

Preen Oil Gland Adaptation

A gland near the tail of the Black-throated Loon (Gavia arctica) used to coat feathers in oil, waterproofing plumage and trapping an insulating layer of low-conductivity air.

Dense Bones Adaptation

An adaptation in the Black-throated Loon (Gavia arctica) that reduces buoyancy to make submerging and diving for fish easier.

First Prokaryotes

The earliest cellular organisms that evolved in liquid water approximately $3.5\text{ billion}$ years ago.

First Single-Celled Eukaryotes

Unicellular eukaryotic life forms that appeared in aquatic environments approximately $1.8\text{ billion}$ years ago.

First Multicellular Eukaryotes

Complex multicellular organisms that appeared approximately $1.2\text{ billion}$ years ago.

First Ocean Animals

The earliest marine animal life forms, which evolved approximately $535\text{ million}$ years ago.

First Land Animals

Animal organisms that transitioned from an aquatic environment to land approximately $500\text{ million}$ years ago.