MARINE BIOLOGY NOTES: CHEMICAL AND PROPERTIES OF WATER
WHAT MAKES WATER SO SPECIAL???
I. Necessary for Life
A. A universal molecule, only known in liquid form from Earth
B. 50-95% of all living tissue is composed of water.
II. Properties of Water
A. Polar covalent molecule
B. Has two positive, two negative sites on the molecule
C. Bonds in this fashion to itself:
D. Electronegative bonds between 2 covalent molecules are called "HYDROGEN BONDS"
E. Water, as a whole, is neutral - the charges balance
III. Water resists Changes in Temperature
A. Water bonds to itself strongly so it takes A LOT of energy to break bonds
1. Water will heat up and cool down SLOWER than almost any other material - a good insulator
2. Helps keep animal and plant tissues within the narrow range needed for life (no drastic changes)
B. Water has HIGH point of evaporation, needs LOTS of energy break bonds and let vibrating, hot
molecules escape.
C. Water takes great heat energy in order to melt, energy needed to line up molecules for solid state
D. Water becomes LESS dense when it freezes
1. the molecules "need space" to line up for crystallization,
wind up increasing the volume, decreasing density.
E. Solutes added to water reduce the freezing temperature (keeps oceans liquid, salt will melt icy streets)
IV.Solutions
A. Solubility
1. water is universal solvent - substances LOVE dissolving in water!
2. Polarity accounts for water's solubility
3. POLAR 4. NONPOLAR -
V. ACIDS AND BASES
A. Concept of "hydrogen bond switching"
1. As hydrogen bonds break and reform, there are MOMENTARY IONS being formed
2. HYDRONIUM IONS = H+ ions
HYDROXIDE IONS = OH- ions
B. Distilled water is neutral, in a STATE OF EQUILIBRIUM
C. Acids = m
D. Bases =
E. pH =
F. an acid + base = salt + water (neutralization)
VI. BUFFER SYSTEMS
A. Living organisms need to maintain homeostasis, Use buffer systems to maintain a pH of 6-8.
B. Blood buffer system the most important overall; sea water has natural buffers in it to protect delicate
tissues from harm (gill filaments, eyes, etc).
C. Because of dissolved salts, sea water is naturally basic, ranging from pH 7.8 to pH 8.3.
D. Calcium Carbonate is the most common buffer present in sea water (CaCO3)
BLOOD BUFFER SYSTEM
H+
H2CO3
CARBONIC ACID
HYDRONIUM
+
HCO3 BICARBONATE ION
H+
H2CO3
OH -
H20
H20
+ CO2
VII. SALINITY
A. Dissolved constituents: 99% of dissolved inorganic matter in seawater Cl-, Na+, Mg++, S++, Ca++, K1. Salt (Na+Cl-) "breaks up" when it dissolves and literally surrounds water molecules with positive and
negative ions.
2. While salt amount varies, the RATIOS between ions remains nearly constant (RULE OF
CONSTANT PROPORTIONS.)
a) the ratio of Chlorine to salt ions was found, used in calculating salinity
3. Field biologists use a
a) SALINOMETER
b) REFRACTIMETER
B. Variations in salinity
C. Effects on marine life:
VIII. DENSITY
A. Specific Density of 1.000 = 1 ml of distilled water @ 4o Celsius
1. Average density of sea water = 1.025 g/ml