Review sheet – Chapter 5
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Know that water is a molecule consisting of 2 hydrogen atoms sharing their electrons with 1
oxygen atom (H2O)
Understand that an atom consists of protons (+), neutrons (=), and electrons (-)
Know that elements in their pure form are quite rare (this is because their outermost electron
shell is incomplete, and so they tend to gain, lose, or share electrons)
Know that an element containing one electron too many in its outermost electron shell will
likely donate (give away) the extra electron, and that when this happens, the element will have
a (+) charge (having now 1 more proton than electrons)
Know that an element containing one electron too few in its outermost electron shell will likely
gain an electron from another element, and that when this happens, the element will have a (=)
charge (having now 1 more electron than protons)
Know that an atom/element has 2 electrons in its innermost shell (closest to the nucleus) and
that each outer shell will hold up to 8 electrons
Know that sodium chloride (NaCl) results from an ionic bond between Na+ and Cl- after Sodium
(Na) donates its extra electron to Chlorine (Cl).
Understand that ionic bonds exist between 2 ions (charged atoms)
Understand that a covalent bond occurs when 2 or more atoms share electrons
Know that covalent bonds are very strong
Know that water (H2O) is a covalently-bonded molecule
Understand that water is a polar molecule, resulting from the shared electrons spending more
time near the oxygen atom than the hydrogen atoms
Know that the bonds that exist between 2 polar molecules are called hydrogen bonds
Understand that the hydrogen bonds in water help moderate temperature; know that heat
must be absorbed to break hydrogen bonds, and that heat is released when hydrogen bonds
form
Understand that oceans moderate global climate by absorbing solar energy and transporting
this heat elsewhere via clouds and precipitation
Understand that tropical storms such as hurricanes helps moderate global climate by
transporting heat absorbed in the tropics poleward
Understand that because of the hydrogen bonds in water, ice is less dense than liquid water
Know that water is a universal solvent because of the polarity of the water molecules
Know that the typical salinity of seawater is ~3.5% or 35‰
Know the major solutes of seawater: chlorine, sodium, sulfur, magnesium, calcium, and
potassium
Know that the ‘salts’ (solutes) in seawater originate from rivers, weathering of rocks, volcanic
activity and outgassing of rift vents
Know that the ratio, or percentage of each solute in seawater is always constant regardless of
how low or high the salinity is (principle of constant proportions)
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Know that the rate at which an element is added to the ocean (source) is equal to the rate at
which the element is removed (sink)
Understand that because of the principle of constant proportions, one can measure salinity by
measuring any of the solutes dissolved in seawater; scientists typically measure chlorinity to
determine salinity
Understand that electrical conductivity of seawater increases with increasing salinity
Know the major gases dissolved in seawater: nitrogen, oxygen and carbon dioxide
Know that nitrogen constitutes the most abundant gas dissolved in seawater, but that most of it
is unavailable to life forms since it exists as N2 (not bioavailable)
Understand that dissolved oxygen is essential for aerobic organisms, and comes from
photosynthesis and diffusion from the atmosphere
Know that carbon dioxide combines chemically with water to produce carbonic acid, and as a
result, the oceans can hold a tremendous amount of CO2
Know that the concentration of carbon dioxide (CO2) is relatively low at the surface because it is
taken up during the process of photosynthesis, while the concentration of oxygen (O2) is
relatively high because it is produced at the surface during photosynthesis
Know that cold water can contain more dissolved gases than warm water
Understand that the concentrations of dissolved gases vary with depth
Know that seawater has a pH of ~7.8, which is slightly basic
Understand that the density of seawater depends mainly on its temperature and salinity; fresh
water is less dense than salt water; warm water is less dense than cold water
Know that the ocean is divided into 3 density zones: surface zone, pycnocline (which could more
specifically be referred to as halocline or thermocline) and deep zone
Understand that the pycnocline is a region of rapidly increasing density
Know that most of the ocean exists beneath the pycnocline in the deep zone
Understand that the thermocline refers to a region of rapidly decreasing temperature
Understand that the halocline refers to a region of rapidly increasing salinity
Understand that thermoclines are very pronounced at temperate (only seasonally) and tropical
regions, but much less so at polar regions
Know that the thin film of sunlit water at the top of the surface zone is known as the photic
zone; dark water beneath this lies in the aphotic zone
Understand that the ocean absorbs red light first, and blue light last (this is because red light has
a greater wavelength and so less energy, while blue light has a shorter wavelength and so more
energy)
Know that by 600 meters, all visible light has been absorbed (much shallower in coastal regions)
Know that sound travels ~5 times faster through water than through air