Chapter 3: Water and Life Flashcards
polar covalent bonds
in a water molecule, the electrons spend more time near the oxygen than the hydrogen
polar molecule
a molecule (such as water) with an uneven distribution of charges in different regions of the molecule
polarity
- a lack of symmetry
- structural differences in opposite ends of an organism or structure, such as the root end and shoot end of a plant
water’s properties
- cohesive behavior
- ability to moderate temperature
- expansion upon freezing
- versatility as a solvent
cohesion
the linking together of like molecules, often by hydrogen bonds
surface tension
- a measure of how difficult is is to stretch or break the surface of a liquid
- water has a high surface tension because of the hydrogen bonding of surface molecules
adhesion
the clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds
kinetic energy
- the energy associated with the relative motion of objects
- moving matter can perform work by imparting motion to other matter
thermal energy
- kinetic energy due to the random motion of atoms and molecules\
- energy in its most random form
- aka heat
temperature
measure in degrees of the average kinetic energy (thermal energy) of the atoms and molecules in a body of matter
heat
thermal energy in transfer from one body of matter to another
calorie (cal)
- the amount of heat required to raise the temperature of 1g of water by 1°C
- also the amount of heat energy that 1g of water releases when it cools by 1°C
kilocalorie (kcal)
- a thousand calories
- the amount of heat energy required to raise the temperature of 1kg of water by 1°C
joule (J)
- a unit of energy
- 1 J = 0.239 cal
- 1 cal=4.184 J
specific heat
the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1°C
heat is absorbed when…
hydrogen bonds break
heat is released when…
hydrogen bonds form
evaporation (or vaporization)
transformation of a substance from liquid to gas
heat of vaporization
the quantity of heat a liquid must absorb for 1g of it to be converted from the liquid to the gaseous state
evaporative cooling
the process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state
4°C
water reaches its greatest density at ___
solution
a liquid that is a homogeneous mixture of two or more substances
solvent
the dissolving agent of a solution
solute
a substance that is dissolved in a solution
aqueous solution
a solution in which water is the solvent (a solution dissolved in water)
hydration shell
the sphere of water molecules around a dissolved ion
hydrophilic substance
a substance that has an affinity for water
hydrophobic substance
- a substance that does not have an affinity for water
- tending to coalesce and form droplets in water (ex: oil)
molecular mass
- the sum of all masses of all atoms in a molecule
- aka molecular weight
Molarity (M)
a common measure of solute concentration, referring to the number of moles of solute per liter of solution
mole (mol)
- the number of grams of a substance that equals its molecular or atomic mass in daltons
- contains Avogadro’s number of the molecules or atoms in question
Avogadro’s number
6.02x10^23
hydrogen ion (H+)
- a single proton with a charge of 1+
- the dissociation of a water molecule (H2O) leads to the generation of a hydroxide ion (OH-) and a hydrogen ion (H+)
- in water, H+ is not found alone but associates with a water molecule to form a hydronium ion
hydroxide ion (OH-)
a water molecule that has lost a proton
hydronium ion
- a water molecule that has an extra proton bound to it
- H3O+, commonly represented as H+
dynamic equilibrium
water is in a state of _________________ in which water molecules dissociate at the same rate at which they are being reformed
acid
a substance that increases the hydrogen ion (H+) concentration of a solution
base
a substance that reduces the hydrogen ion (H+) concentration of a solution
acidic solutions
solutions with pH values less than 7
basic solutions
solutions with pH values greater than 7
buffer
- a solution that contains a weak acid and its corresponding base
- minimizes changes in pH when acids or bases are added to the solution
ocean acidification
the process by which the pH of the ocean is lowered (made more acidic) when excess CO2 dissolves in seawater and forms carbonic acid (H2CO3)
CO2
the main product of fossil fuel combustion
calcification
the production of calcium carbonate (CaCO3)
water
the most versatile solvent known
polar molecule
a molecule (such as water) with an uneven distribution of charges in different regions of the molecule
