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Chapter 3 Water and Life (3.2 Four emergent properties of water contribute…
Chapter 3 Water and Life
Introduction: The Molecule that supports all of life
water is what makes life possible
exists in all three states of physical matter: solid, liquid and gas forms
a rare property found in water is that its solid form can float on its liquid form
3.1 Polar covalent bonds in water molecules result in hydrogen bonding
polar covalent bond = one element is more electronegative and is more attracted to the electrons than the other
example: H2O; Oxygen is more electronegative than its partner Hydrogen and therefore the electrons stay close to it and they are shared unequally
polar molecule = overall charge of water is unevenly distributed
leading to it being shaped like a V or Mickey Mouse ears
hydrogen bonds are very fragile in the liquid form of water
leads to frequently breaking and forming new bonds
resulting in the amazing emergent properties of water
3.2 Four emergent properties of water contribute to Earth's suitability for life
Introduction
there are four emergent properties that help Earth be a suitable environment for life
cohesive behavior
ability to moderate temperature
expansion upon freezing
versatility as a solvent
Cohesion of Water Molecules
cohesion = clinging of like molecules
adhesion = the clinging of unlike molecules
similar to adhesion is surface tension = a measure of how difficult it is to stretch or break the surface of a liquid
an example of adhesion or surface tension would be of a bug walking on the surface of the water
Moderation of Temperature by Water
Temperature and Heat
kinetic energy = the energy of motion
thermal energy = kinetic energy associated with the random movement of atoms or molecules
heat = thermal energy in transfer from one body of matter to another
calorie = amount of heat needed to raise 1 g of water by 1 degree celsius
kilocalorie (1,000 cal) = amount of heat to raise 1 kg of water by 1 degree celsius
joule = SI unit of work or energy, equals 0.239 cal
temperature and thermal energy are related but temperature = average kinetic energy while thermal energy = total kinetic energy
Water's High Specific Heat
specific heat = amount of heat that must be absorbed or lost for 1 gram to change its temperature by 1 degree celsius (calorie)
water has a high specific heat so it resists changing its temperature and takes longer than other elements would
this is due to its hydrogen bonding
Evaporative Cooling
evaporation = the transformation from a liquid to a gas
during evaporative cooling, the hottest molecules leave water as a gas or vapor
this causes the surface to cool down
Floating of Ice on Liquid Water
water is less dense as a solid than as a liquid
that is why ice is able to float on top of liquid water
Water: the solvent of life
solution = liquid that is a homogeneous mixture of two or more substances
solvent = dissolving agent of a solution
solute = the substance that is dissolved
hydrophilic vs hydrophopic = any substance with an affinity for water is hydrophilic, and any substance that repels it is hydrophobic
Solute concentration in aqueous solutions
molecular mass = sum of the masses of all the atoms in a molecule
molarity = the number of moles of solute per liter of solution
mole (mol) = represents an exact number of objects, Avogrado's Number
3.3 Acidic and basic conditions affect living organisms
Introduction
hydrogen ion = single proton with a positive charge of +1
hydroxide ion = charge of 1-
hydronium ion = water molecule with an extra proton
Acids and Bases
acid = substance that increases the hydrogen ion concentration of a solution
base = a substance that reduces the hydrogen ion concentration of a solution
The pH Scale??
the measuring scale of whether something is more acidic or basic
represents H+ and OH- concentrations
Buffers
buffer = substance that minimizes changes in the concentrations of H+ and OH- in a solution
allows biological fluids to maintain a relatively constant pH despite the addition of acid or bases
Acidification: A threat to our oceans
ocean acidification = process of CO2 dissolving in seawater and reacting with it to form carbonic acid which then lowers ocean pH
ocean acidification alters the delicate balance of conditions for life in the oceans
