5-3 The Water Molecule

Gases in seawater

in decreasing abundance, include nitrogen, oxygen, carbon dioxide, hydrogen, and the noble gases argon, neon, and helium. nitrogen and the three noble gases are inert (unreactive) and rarely involved directly in plant photosynthesis. Levels of dissolved oxygen and carbon dioxide are greatly influenced by photosynthesis and respiration of organisms. They vary greatly in space and time depending on the activity of plants and animals and are regarded as nonconservative.

Solvent

the dissolving agent of a solution; liquid water

What does seawater contain?

Seawater contains salt ions (sodium and chloride) and minor to trace amounts of dissolved metals, nutrients, gases, and organic compounds of seemingly infinite variety.

Solvent power

The capability of liquid water to dissolve material. Water is the "universal solvent," meaning that virtually anything can be dissolved to some extent in water. Depends on the dipole structure of its molecule. Because of this, ocean water dissolves many types of chemicals, and most are found in minute quantities.

solar heat

(energy from the sun)- The sun hits the surface of Earth at varying angles, which causes major climates to be present in certain areas, as well as influencing the type of life forms that exist in those various regions. Also affects the Earth's weather, which affects the vegetation and conditions like erosion. During the summer, large bodies of water absorb solar heat, helping keep air temperatures cool. During the winter, large lakes and the ocean radiate great quantities of stored heat to the atmosphere as their water cools, warming the adjacent shoreline.

Ionic bonds

the electrostatic forces that hold ions together in ionic compounds opposing charges are attracted to each other

Saturation

the state or process that occurs when no more of something can be absorbed, combined with, or added.

covalent bond

A chemical bond that involves sharing a pair of electrons between atoms in a molecule. The hydrogen and oxygen atoms share electrons, and form a covalent bond.

Hydration

A chemical process that results in water being absorbed or added to a compound. The cations keep separated from anions. The water acts as a solvent by preventing the chemical recombination of Na+ and Cl- to form the solid halite.

polymers

A loose collection of water molecules that approximate the hexagonal crystalline structure of ice.

Dipole

a molecule that has two poles, or regions, with opposite charges the higher-than-expected melting and boiling temperatures of water depend directly on the ______ structure.

hexagon

a six-sided structure H2O molecules in ice are ordered into a porous ______ by the hydrogen bonds between oppositely charged ends of neighboring molecules.

Nutrients

a substance that provides nourishment essential for growth and the maintenance of life. are essential for plant growth. all plants convert _____ into food (organic compounds such as sugar) by photosynthesis. Compounds that primarily consist of nitrogen, phosphorous, and silicon. The concentrations are specified in parts per million (ppm). Most plants absorb phosphate and nitrate. Because of biological uptake and release, the concentration of _______ in seawater vary from place to place and over time at any one place. These substances are nonconservative ions of seawater, signifying that levels of these substances are not constant in water but vary over time and from place to place.

parts per thousand (ppt)

the concentration of a solute in seawater in units. represented as the symbol 0/00. Example: average seawater has a salinity of about 35 0/00. This means that the dissolved salt occurs in the concentration of 35 parts per thousand (ppt). That is, 3.5% of the sample. The rest, 96.5% is H2O molecules.

Solute

the substance that is dissolved; salt ions

Major constituents

vary little over time as most localities, described as conservative ions of the ocean. The primary solutes in seawater are cations and ions. By weight, chloride and sodium together compromise more than 85.65% of all dissolved substances in water. When these two ions bond chemically into a solid, they form halite and give seawater its saltiness. The six most abundant ions = chloride, sodium, sulfate, magnesium, and potassium - make up over 99 percent of all seawater's solutes. Bicarbonate, bromide, boric acid, strontium, and fluoride = 99.99 percent.

Organic compounds

Large, complex molecules produced by organisms. Include substances such as lipids (fats), proteins, carbohydrates, hormones, and vitamins. They occur in low concentrations and are produced by metabolic (physical and chemical processes in the cell of an organism that produce living matter) and decay processes of organisms.

Density of water

is unusual property of water. ice floats on water because ice molecules are arranged into an open crystal framework whereas liquid water molecules are packed into snug clusters by the hydrogen bonds between molecules. Ice is 8 percent less dense than water. Water does not reach its maximum density until it is warmed to 3.98 degrees Celsius because loose aggregates of molecules that resemble the open crystalline structure of ice persist in water cooler than that critical temperature. Above 3.98, the density of water decreases with increasing temperature. However, below 3.98, the density of water decreases as temperature decreases until it freezes into ice.

Halite

rock salt or common table salt ionic bonding NaCl

the chemical formula for water

H2O 2 hydrogen atoms chemically bonded to one atom of oxygen Only substance that can coexist naturally as a gas, a liquid, and a solid on the Earth's surface. Fundamental to all forms of life. The two hydrogen atoms are separated from each other by an angle of 105 degrees for water in the liquid and gaseous states. This molecular architecture resembles a mouse's head with hydrogen ears. Dipole structure Covalent bonding. Each hydrogen atom possesses a single positive charge and the oxygen atom possesses a double negative charge. The H2O molecule is electrically neutral because of the balance between the positive and negative charges.

What happens wen halite crystals are put in water?

The negatively charged end of the H2O dipole dislodges sodium ions (Na+) from the solid, and the positive end of the H2O molecule tears off the chloride ions (Cl-). Dissolution continues until either the entire crystal of halite is gone or the volume of water can no longer accommodate more ions of salt because it is saturated.

heat capacity of water

Water has a relatively high heat capacity and tremendous solvent power. The quantity of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius. More energy is required to raise the temperature of a substance with a high heat capacity than one with a low heat capacity. This explains why so much energy is required to heat water. Prevents extreme variations in the temperature of the oceans and explains why the climates of the coasts and islands experience less extreme temperature variations than those of land located far from the ocean or large lakes.

Hydrogen bonding in water

Water molecules are polar and hydrogen bonds form between them. Electrostatic bonding. Produces irregular chains and clusters of H2O molecules. Cluster sizes decrease with increasing temperature. Not as strong as covalent bonding. More energy is required than expected to vaporize liquid water and to melt ice because of this bonding. Reason for water's high heat capacity. Much of the heat added is used to break these bonds that link the H2O molecules into irregular clusters. Thus, as water is heated, its temperature rises slowly relative to the amount of energy used. When cooled, water releases more heat then expected from the decrease in temperature.

Trace elements

all chemical ingredients that occur in minute (_____) quantities in the oceans. comprises only 0.01 percent of seawater. Include manganese, lead, mercury, gold, iodine, and iron. Occur in concentrations of less than 1 ppm (part per million or 1 part per billion (ppb) or even 1 part per trillion. Difficult and often impossible to detect in seawater Can be critically important for marine organisms, either by helping to promote life or by retarding or killing life (toxicity).

Anion

an ion with a negative charge example: Chloride (Cl-)

Cation

an ion with a positive charge example: Sodium (Na+)