Marine Ecology and Oceanography: Properties of Seawater

Flashcards covering the chemical and physical properties of seawater, including atomic structure, water molecule characteristics, salinity principles, and oceanographic measurement tools.

Atoms

The smallest units that display all the properties of a material, consisting of a nucleus (protons and neutrons) and orbiting electrons.

Ions

Atoms that are electrically charged because they possess either more or fewer electrons than protons.

Relative mass of a Neutron

$$1.674927351(74) \times 10^{-27}\,kg$$

Relative mass of a Proton

$$1.672621777(74) \times 10^{-27}\,kg$$

Relative mass of an Electron

$$9.10938291(40) \times 10^{-31}\,kg$$

Isotopes

Atoms containing the same number of protons but different numbers of neutrons, resulting in different atomic weights.

Calorie

The amount of heat needed to raise the temperature of $1\,gram$ of water by $1^\circ C$.

Density

The ratio of mass to volume ($\text{mass/volume}$); it decreases as temperature increases because atoms or molecules move farther apart.

Water Molecule Structure

An asymmetric molecule consisting of two hydrogen atoms bonded to one oxygen atom with an angle of $105^\circ$ between them.

Dipole structure

The electrical property of water where there is a positive charge on the hydrogen side and a negative charge on the oxygen side.

Hydrogen bond

An electrostatic bond produced between water molecules due to their dipole structure, causing them to cluster together.

Latent heat of melting

$$80\,cal/g/^\circ C$$

Latent heat of vaporization

$$540\,cal/g/^\circ C$$

Marine effect

The phenomenon where oceans moderate temperature changes during the day and night as well as across different seasons.

Continental effect

The tendency of land areas to experience a greater range of temperatures during the day, night, and throughout different seasons compared to oceans.

Hydration

The process of water molecules surrounding an ion and neutralizing the ionic bond holding a salt molecule together.

Maximum Density of Water

Water reaches its maximum density at a temperature of $3.98^\circ C$.

Salinity

The total amount of salts dissolved in water, generally expressed in parts per thousand ($\text{ppt}$ or $\text{‰}$).

Conservative ions

Salt ions, such as sodium and chloride, whose relative proportions in the sea remain constant over time.

Non-conservative constituents

Substances like nutrients (nitrogen, phosphorus, silicon) whose concentrations are highly variable due to biological activity and uptake.

Trace elements

Elements occurring in minute quantities, measured in parts per million ($ppm$) or parts per billion ($ppb$), such as $Fe$, $Mn$, and $Zn$.

Principle of constant proportion

The principle stating that while the absolute amount of salt in seawater varies, the ratio of any two salt ions remains constant.

Chlorinity

The amount of halogens in seawater, expressed as $\text{grams/kilogram}$ or $\text{‰}$, used to calculate salinity via the formula: $\text{Salinity (‰)} = 1.80655 \times \text{chlorinity (‰)}$.

Salinometer

An instrument that determines salinity by measuring the electrical conductivity of seawater.

Residence time

The average length of time that an ion remains in solution in the ocean.

Mixing rate of oceans

$$10^3\,years$$

Freezing point of Seawater

For seawater with a salinity of $35\text{‰}$, the freezing point is $-1.91^\circ C$.

Vapour pressure

The pressure exerted by the gaseous phase on the liquid phase; it decreases as salinity increases.

Niskin bottle

A tool used to collect water samples at specific discrete depths.

CTD

A sensor used to measure conductivity (salinity), temperature, and depth (pressure) in seawater.