Unit 1 (Ch. 1-5) Flashcards
essential element
a chemical element required for an organism to survive, grow, and reproduce
trace element
an element indispensable for life but required in extremely minute amounts
half-life
the amount of time it takes for 50% of a sample of a radioactive isotope to decay
radiometric dating
a method for determining the absolute age of rocks and fossils, based on the half-life of radioactive isotopes
valence electrons
an electron in the outermost shell
valence shell
the outermost electron shell
orbital
3 dimensional space where an electron is found 90% of the time
double bond
sharing two pairs of valence electrons
electronegativity
the attraction of a given atom for the electrons of a covalent bond
non polar covalent bond
electrons are shared equally between two atoms of similar electronegativity
polar covalent bond
a covalent bond between atoms that differ in electronegativity. the shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
hydrogen bond
weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule
van der Waals interactions
weak attractions between molecules or parts of molecules that result from transient local partial charges
chemical equilibrium
the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time
cohesion
the linking together of like molecules, often by hydrogen bonds. the tendency for water to stick to other water molecules.
surface tension
results from cohesion due to hydrogen bonding, how difficult it is to stretch or break the surface of a liquid
adhesion
the clinging of one substance to another
thermal energy
the kinetic energy associated with the random movement of atoms or molecules
calorie (cal)
the amount of heat it takes to raise the temperature of 1g of water by 1 degrees C
specific heat
the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1 degrees C
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
as a liquid evaporates, the surface of the liquid that remains behind cools down
solution
a liquid that is a completely homogeneous mixture of two or more substances
solvent
the dissolving agent
solute
substance that is dissolved
hydration shell
the sphere of water molecules around a dissolved ion
hydrophilic
affinity for water, polar
hydrophobic
repels water, non polar
molarity
number of moles of solute/liter of solution
hydrogen ion
a single proton with a charge of 1+
hydroxide ion
OH- with a charge of 1-