Ch. 2: Chemistry Flashcards
Atom
nucleus of positively charged protons and neutrally charged neutrons with negatively charged electrons outside nucleus
Molecules
groups of two or more atoms held together by chemical bonds,
formed by interaction of their electrons
Electronegativity
ability of an atom to attract electrons,
plays large part in determining kind of bond formed
Ionic Bond
electrons transferred,
electronegativities v different and one atom has much stronger pull on electron (high electronegativity)
Ion
atom with charge;
gain electron –> (-) lose electron –> (+)
Covalent Bond
electrons between atoms shared,
electronegativities between atoms are similar
Nonpolar Covalent
electrons shared equally,
electronegativities are equal and atoms pull equally, (O2)
Polar Covalent
electrons shared unequally, atoms have different electronegativities so one pulls electron more
Pole
during polar covalent bond, atom with greater electronegativity holds electrons closer and produces a negative charge (pole); other atom forms positive pole
Example: H20 (O more electronegative)
Hydrogen Bond
weak bonds between molecules form when (+) charged H atom in one covalent molecule is attracted to a (-) area of another covalent molecule in water (+) H forms H bond w/ (-) O of another molecule
Properties of water
excellent solvent high specific heat capacity ice floats has strong cohesion and high surface tension has strong adhesion
Water as solvent
ionic substances soluble in water bc poles of water molecules separate them into ions, polar covalent molecules work similarly
so many molecules dissolve in water –> universal solvent
Hydrophilic
“water loving,” dissolve in water because are charged
Hydrophobic
“water fearing,” nonpolar covalent substances lack charged poles and do not dissolve in water
Solute
substance that dissolves solvent
Aqueous solution
water is the solvent
Specific heat
degree to which a substance changes temperature in response to gain or loss of heat
Water’s high specific heat
changes temperature v slowly w/ changes in heat content have to add large amounts of energy to warm water or remove lots to cool evaporative cooling (sweat)
Water changing state
when heated (solid-->liquid-->gas) energy is absorbed and breaks H bonds, keeping temp. constant when cooled this is reversed, and H bonds are formed with the released energy
Heat of fusion
energy requited to change water from solid to liquid
Heat of vaporization
energy required to change water from liquid to gas
Ice floats
water expands as it freezes and becomes less dense than the liquid form
weak H bonds constantly break and reform in liquid state while in ice, H bonds between water molecules become rigid in a honeycomb arrangement
Implications of ice floating
if ice didn’t float it would sink and remain frozen due to the insulating protection of the overlaying water so would profoundly affect the survival of the organisms living at the bottom of the water
Water has strong cohesion and surface tension
H bonds cause cohesion and water sticks together, this forms high surface tension so creating a water surface firm enough to allow many insects to walk upon w/out sinking
Water has strong adhesion
water attracts to unlike substances as its poles attract to poles of other substances (wetting finger to turn pages)
demonstrates capillary action (plants)
Capillary action
water’s adhesion to the walls of narrow tubing or absorbent solids like paper it rises up, defying gravity
Organic molecules/ macromolecules
have carbon, easy to bond w/ bc 4 electrons available to form covalent bonds
straight lines or rings
monomers made from polymers
Hydroxyl group
-OH
Ex.: alcohols (ethanol), glycerol, sugars
polar, hydrophilic
Carboxyl group
-C–O/-OH
Ex.: acetic acid, amino acids, fatty acids, sugars
polar, hydrophilic, weak acid
Amino group
-N-H/-H
Ex.: amino acids
polar, hydrophilic, weak base
Phosphate group
-P–O/-O(-)/-O(-)
Ex.: DNA, ATP, phospholipids
polar, hydrophilic, acid
Methyl group
-C-H/-H/-H
Ex.: fatty acids, oils, waxes
nonpolar, hydrophobic
