Chemistry 105 Midterm 1

solid

definite shape and volume

liquid

definite volume, indefinite shape

gas

neither definite volume or shape, includes plasma

sublimation

solid to gas

deposition

gas to solid

freezing

liquid to solid

melting

solid to liquid

condensation

gas to liquid

vaporization

liquid to gas

intensive property

matter dependent property, independent of material quantity; i.e temperature, density

extensive property

property independent of matter, dependent on quantity of substance; i.e mass, volume, length

physical property

observed/measured without changing a substance into another; easily reversible

chemical property

observed only by reacting a substance to form another

chemical reaction

process in which composition and structure change during a reaction

energy

ability to do work

potential energy

energy stored by position, internal stress, electrical charge, or other factors

kinetic energy

energy of motion

law of conservation of mass

matter is not created nor destroyed in any chemical or physical change

pholgiston

material that escapes when substance is burned

law of definite proportions

a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound

law of multiple proportions

elements can combine in different ratios to form different compounds

modern view of atom

atoms are unchanged by a chemical reaction, elements are distinguished by the number of protons, can combine in different ways; small nucleus surrounded by electron cloud

molecular formula

shows the types and numbers of atoms combined in a single molecule of a molecular compound

structural formula

indicates the kind, number, arrangement, and bonds but not the unshared pairs of the atoms in a molecule

condensed formula

shows patterns of arrangement, no structural elements

ball and stick model

bonding arrangement showing spatial orientation and size comparison

space filling model

overall shape, more accurate representation

accuracy

closeness of measured value to true value

precision

degree to which repeated measurements show the same result; express variance as a range

captive zero

always significant

leading zero

never significant

trailing zero

significant if decimal point is present

addition/subtraction

least number of decimal places

multiplication/division

least number of sig figs

robert boyle 1661

defined element; elements are not air, earth, water, fire; matter based on observation and demonstration

antoine lavoiser 1774

law of conservation of mass; accurate measurements, matter is neither created nor destroyed

joseph proust 1799

law of definite proportions; pure substances consist of elements in definite/fixed proportions

john dalton 1808

law of multiple proportions; atomic theory; when mass of one element is fixed, masses of other element will be a ratio of whole numbers; elements composed of atoms

hard sphere model

john dalton; indivisible hard spheres with hooks to form molecules

coloumb's law

strength depends on magnitude of charge and distance between two charged particles

cathode ray tube

jj thomson; created stream of particles that can be deflected by magnet, proving negative particles existed. deflection by electric and magnetic field gave charge/mass ratio

millikan oil drop

1909, designed to measure electron charge. x-rays ionize air to transfer electrons onto droplets, magnetic field applied and charge measured based on the balance of gravity and charge

marie curie

positively charged particles, studied uranium, explained that radioactivity is the spontaneous decomposition of atom

wilhelm roentgen

discovered x-rays in 1895

henri becquerel

discovered radioactivity in 1896

alpha particles

positively charged particles with about four times the mass of a hydrogen atom; least penetrative

beta particles

a negatively charged particle (a high speed electron) emitted from the nucleus of an atom during radioactive decay

gamma ray

the high-energy photon emitted by a nucleus during fission and radioactive decay; neutrally charged, highest penetrative ability

plum pudding model

J.J Thomson; model of an atom where electrons were randomly distributed within a positively charged cloud; 1904

ernest rutherford

1909; solar system model of the atom, gold foil experiment; fired negative ions at thin sheet of gold foil, discovered the positively charged atomic nucleus and proposed a nuclear model of the atom in 1911

james chadwick

discovered the neutron in 1932

isotope

atoms of the same element that have different numbers of neutrons

dmitri mendeleev

russian chemist who developed a periodic table of the chemical elements and predicted the discovery of several new elements based on patterns in chemical properties (1834-1907)

columns

groups or families that have similar properties,
same number of valence electrons and similar charges

periods

horizontal rows, have same number of electron shells

metals

shiny solids (except mercury), high melting points, high densities, malleable, ductile (drawn into wires), good conductors of heat and electricity, form cations and basic oxides

non metals

dull, brittle, poor conductors of heat and electricity; form anions, ionic compounds, and acidic oxides

metalloids

elements that have properties of both metals and nonmetals; antimony (Sb), germanium (Ge), silicon (Si), arsenic (As), tellurium (Te), polonium (Po), boron (B), and astatine (At)

alkali metals

group 1, always water soluble

alkaline earth metals

group 2, sometimes water soluble, reactivity increases down group

halogens

group 17, diatomic, forms anions, reactivity increases up group, reacts with metals to form metal halides, disinfectants

noble gases

group 18, unreactive, do not easily gain or lose electrons

atomic mass

the average mass of all the isotopes of an element

mass spectrometer

an instrument used to determine the relative masses of atoms by the deflection of their ions on a magnetic field; radius of curve depends on the mass and charge of particles

electromagnetic radiation

proposed in 1800s, described as moving wave of energy with two perpendicular oscillating fields

peak/crest

top of wave

trough

bottom of wave

amplitude

height of crest or depth of trough

wavelength

distance between two corresponding parts of a wave

frequency

the number of complete wavelengths that pass a point in a given time

intensity

amount of energy per second carried through a unit area by a wave; amplitude squared

node

point of zero amplitude on a standing wave

rays in increasing wavelength

gamma rays < x-rays < ultraviolet < visible < infra red < microwave < radio waves

colors in increasing energy

violet > blue > green > yellow > orange > red

1900s physics

light defined by Maxwell's equations, motion defined by Newton's equations; most problems solved and understood

blackbody radiation

the electromagnetic radiation emitted from a heated solid

photoelectric effect

the emission of electrons from a metal when light shines on the metal

ultraviolet catastrophe

classic physics predicted spectrum of emitted blackbody radiation should extend without bound into the ultraviolet, resolved by Plank's hypothesis that the oscillating waves exchange energy in quanta

max plank

1900, light has particle like properties and wavelike characteristics; objects absorb/emit energy in small, specific quantities called quanta into the ultraviolet; related energy absorbed by matter to frequency of light emitted

photoelectric observations

no electrons emitted for low frequency light regardless of intensity; electrons emitted above specific threshold frequency; number of electrons emitted increases with intensity; velocity of ejected electrons increases as frequency increases beyond threshold

albert einstein

1905, concluded light itself is quantized in photons; classical views light as wave, einstein viewed light as particle; light is both

work function

minimum amount of energy to remove one electron, any excess energy is converted to kinetic energy of ejected electron, cannot exceed energy of a single photon of wavelength λ

spectrum

set of wavelengths

continuous spectrum

the emission of a continuous range of frequencies of electromagnetic radiation

fraunhofer lines

1814, a set of dark lines in the otherwise continuous solar spectrum - sunlight is not continuous

bunsen and kirchoff

1859, each element emits unique set of wavelengths

emission

when an electron falls to a lower energy level, a photon is emitted, giving off colors

absorption

absorbed colors are subtracted from continuous spectrum in the appearance of black lines

emission and absorption relationship

a gas absorbs colors when cold that it emits when hot

balmer lines

a series of absorption or emission lines of hydrogen seen at visible wavelengths

bohr model

1913, electrons can only occupy certain stable orbits, "allowed" orbits have quantized angular momentum and quantized energy; electrons can jump between orbits by absorbing or emitting light

n

principal quantum number, designates energy level and orbital size; 1, 2, 3, 4

n = 1

ground state, lowest possible energy level

n > 1

excited state

lyman series

set of spectral lines that appear in the UV region when a hydrogen atom undergoes a transition from energy levels n>1 to n=1

paschen series

set of spectral lines that appear in IR region when electron falls from n>3 down to n=3

energy as n approaches infinity

approaches 0

limitations to bohr model

limited to atom with single electron; doesn't explain WHY angular momentum and energy levels are quantized or why n=1 is lowest energy level

solar sail

einstein says momentum=h/λ; shorter wavelength has higher momentum and light acts like a particle

louis de broglie

moving objects have wave-like behavior; matter shows properties of both wave and particles