Chem 6A Midterm 1: Sxn A,b,e & Ch. 1

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substance

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Pure

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mixtures

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2 or more substances

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heterogenous mixtures (example)

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of variable composition (sand in water)

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homogeneous mixtures (example

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of uniform composition (salt in water)- aka solutions

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what are the states of matter?

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solids, liquids, gases & plasma

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solids

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have a defined volume & shape/highest density

*like a housing tract- your neigbors stay where they are

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liquids

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have a defined volume & take the shape of container/nearly as dense as solids (except H2O- liquid H2O is more dense than solid H2O)
*like a mosh pit- liquid molecules are more promiscous

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Gases

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take volume and shape of container/ known as "perfect fluid"

*gases have no neighbors- they like to be left alone & they expand to distance themselves

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standard state

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the state a material assumes at room temperature at 1 atm/ aka "normal"

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physical changes

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can be measured and documented/ the identity of the compound does not change
example: H2O(s)+heat--> H2O(l)

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chemical changes

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the identity of a material changes (the chemical compound undergoes a change-elements rearange)/identities of elements do not change
example:CH4(g)+O2(g)+heat-->CO2(g)+H2O(l)

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What are the 2 types of physical properties?

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extensive properties & intensive properties

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extensive properties (example)

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depend on the amount of the item studied (the size of a fire is larger when there is more wood- size is the extensive property)

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intensive properties (example)

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not dependent on the amount of the item studied (temperature in a room does not fluctuate due to size of room-temperature is the intensive property)
*can be ratios of extensive properties

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Density

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equal to mass over volume (D=m/v)/an intensive property even though mass & volume are both extensive properties

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energy

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the capacity to do work/the movement of mass some distance over time

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work

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the directed flow of energy/force through distance/measured in joules (J)

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Joules (J)

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1J= 1kg-m²/sec²

*kg-m²=kg•m² (units can only be multiplied)

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what are the 2 types of energy for particles?

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kinetic energy & potential energy

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kinetic energy

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due to movement/
Ek=½mV²

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potential energy

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due to position-is a function of the forces that act on it (ex. gravity)/
Ep=mgh=mass•grams•height

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electromagnetic energy

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moves in space from one location to another (ex.heat)

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Coulombic force

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the force that a charged particle feels(the charge of particles and the distance between 2 fiven particles affects the amount of force felt)

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what is the equation/ratio of coulumbic force?

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F= q1q2/4πEo•r
(the coulubic force is equal to the charge of particle 1 times particle 2 divided by 4π times the permitivity of the vacuum times the distance between the particls)
qx(charge of particle in coulumbs c)=Qxe
Qx=nominal charge of particle
e=fundamental charge in coulombs=1.602•10^-14 c
r=distance between 2 particles
Eo=permittivity of vacuum=8.854•10^-12c²/J-m

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nominal charge

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can be (+) or (-)
example: for Ca^2+, Q=+2
example: for S^-2, Q=-2

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negative force

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when the sign of a force is negative, there is strong interaction/if the force is more negative, the interaction is stronger/everything tries to have negative force (negative force means potential energy)/if the sign of force is negative, the system is losing energy, when systems lose energy, they drop to a lower energy state and become more stable

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summary of coulumbic effect (if u dont need real numbers)

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F=Ep Q1Q2/r

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electromagnetic radiation (EMR)

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the energy of an electromagnetic field/it is generated by acceleration of charged particles/consists of an oscillating electric field perpendicular to an oscillating magnetic field

*speed of an EMR wave is constant- c=λv

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oscillating electric field

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affects a stationary or moving particle

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oscillating magnetic field

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affects charged and moving particles

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total particular energy

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is equal to the kinetic energy of a particle plus the potential energy of the paticle/
Ept=Ek+Ep

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the law of conservation/aka the first law of thermodynamics

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when energy is lost from one place, it must be gained elsewhere-energy cannot disappear

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system

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what we are studying

*energy out of the system goes into the surroundings/energy flow is defined by the system

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surroundings

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everything outside of the system
(ex. the beaker in which a chemical reaction occurs)

*energy ot of the surroundings goes into the sytem

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thermodynamic universe

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the system plus the surroundings

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heat

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q

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work

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w=motion agains an opposing force

*w=+ if work is done on the system/w=- when the system does work

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atom

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the smallest particle of an element that can exist and still exhibit properties of the element

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John Dalton

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school teacher/advocate of the atomic theory/said an atom is like a rubber ball (real life says an atom is composed for subatomic particles)

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the atomic theory

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a unifying theory of the nature of matter
1.all atoms of a given element are identical
a.chemically correct
b.physically incorrect/while all atoms of a given element have the same mass, the isotopes of a given element differ from eachother
2.atoms of different elements have different properties, most notably mass
3.compounds are formed by specific combinations of 2 or more elements or when 2 or more atoms join together
4.atoms are conserved,never created or destroyed
a.atoms recombine during chemical reactions

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JJ Thomson(1897)

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used a cathode ray to find the atoms negatively charged electrons-heated metal to produce a quantized beam of rays that showed up on a phosphorescent screen/cathode ray

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cathode ray

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isnt really a ray, but instead a stream of negativley charged particles called electrons

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millikan's oil drop experiment

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a charged oil was dropped between 2 charged plates in which a variable electric field has been established/millikan adjusted the field until the drop was suspended in the middle of the plates

*from this,he figured out that the mass of an electron is equal to 9.1•10^-31kg & that the charge on an oil drop had to be an integer

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the plum pudding model

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knowing that the charge of an atom is neutral,Lord Kelvin suggested that the negative electrons were suspended in a positively charged jelly, which made up the atom

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Rutherford

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tried to prove the plum pudding model

*his experiment (with geiger and marsden) indicated that the atoms within the foil had a dense,internal positive core & thus ruined the idea of the plum putting model

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composition of an atom

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the # of protons(+) tells the identity of an atom/ the # of neutrons(0) identifies the different isotopes of an element/ the # of electrons(-) is responsible for the chemistry of an element

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isotopes

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atoms with the same # of protons but different # of neutrons/have the same atomic #(Z), but different A values

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nuclear atom

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constructed after thomson and rutherfords experiments/in the nuclear model the nucleus is constructed of protons(about 2000 times more massive than an electron) & neutrons(slightly heavier than porton)/the nucleus makes up 98% of the mass of an atom

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atomic number

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Z=the number of protons in a given atom/discovered by moseley

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neutrons

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detected in the atom by scientists who noticed that, while the # of protons changes from element to element on the periodic table by only 1, the mass from element to element increased by more than the weight of 1 proton-decided that there were particles other than protons in the nucleus that act as a glue to hold the nucleus together

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nuclear number

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A=the # of protons + the # of neutrons/
A=p(+)+n(0)

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average atomic mass

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∑iª(fractional abundance i)•(atomic mass i)

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moles

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1 mole (mol)= the number of objects equal to the number of atoms present in exactly 12 grams of Carbon-12/
1mol C-12 atoms= 12g C-12 atoms= 6.022•10^-23 C-12 atoms

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avagadro's number/constant

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NA=6.022•10^-23 items/mol

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atomic weight/atomic mass

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used with single atoms

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molecular weight/molecular mass

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used with covalent compounds

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formula weight/formula mass

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used with ionic compounds

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black body/black body radiation

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absorbs and emits all wavelengths without preference/when u heat a black body, it becomes incandescent

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the stefan-boltzmann law

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stefan & boltzmann figured out how to explain the change in intensity (incandescent)--the total intesity of radiation emitted by a black body is proportional to the temperature in Kelvins raised to the fourth power

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Wein's law

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accounted for shorter wavelengths in terms of a "red shift"/means that the emitted light is proportional to 1 over the temperature in kelvins(λmax is proportional to 1/T)/
Tλmax=1/5C2
(C2 is the "2nd radiation constant"/C2=1.44•10^-2Km)

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the UV catastrophe

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classical mechanics predicted that any black body with a nonzero temperature would emit UV, gamma, & cosmic rays--this would mean we glow in the dark

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Planck

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a classical physicist/proposed that energy occurs in packects (quanta)/had to discard classical physic's idea that there is no limit on an amount of energy being transferred/later tried (unsuccessfully) to disprove his theory of quanta

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quanta

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packets of energy/transfer energy between matter and radiation/but only certain packets can transfer--means that energy travels in discrete amounts

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energy exchange

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an atom oscillating at a given frequency could only exchange energy according to the equation: E=nhv
(n=an integer,h=plancks contant=6.626•10^-34J•sec)/meant radiation could only be generated if a transmitter has acquired enough energy to begin oscillating

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planck's constant

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h=6.626•10^-34J•sec

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the photoelectric effect

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defines what happens when a certain metal is hit with UV radiation
1.if u vary the amount of UV radiation, eventually an electron will jump
2.no electron will jump unless energy is above threshold value
3.the kinetic energy of the ejected electron increases lineraly with the frequency (v is proportional to Ke-)

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threshold value

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the point at which there are enough oscillations for an ejection to occur/if the energy is below threshold value, nothing happens/energy at threshold value results in the immediate ejection of an electron

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photons

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Einstein: electric energy consits of photons (packets of energy), where E=λv

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intensity of radiation

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proportianal to the # of protons being emitted/
N=λPt/he
(N=number of photons,h=planck's constant,c=speed of light,t=time,λ=wavelength,P=the power of light measured in watts (J/sec))

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diffraction

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the deflection of waves and the resulting interference caused by an object in their path

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constructive interference

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interference that results in an increased amplitude of a wave

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desctructive interference

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interference that results in a reduced amplitude of a wave

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wave nature of particles

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shown by diffraction, constructive interference & destructive interference

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wave-particle duality

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states that energy is a particle, a particle (matter) can be described as a wave/de Broglie:matter has a wavelength/
λparticle=h/p=h/mv
(p=momentum,m=mass &v=velocity)--says large items have small wavelengths

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trajectory

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the path of a particle on which location and linear momentum are specified at each instant

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heisenberg uncertainty principle

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where the charge in momentum times the change in position is greater or equal to one-half h-bar/only works for small particles

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wave function

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Ψ=a function that varies in value as a function of position/
Ψ=RY
(R=a radial measure & Y=an angular measure)

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probabilty density (of a particle)

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a function that, when multiplied by the volume of the region, gives the probability that the particle will be found in that region of space

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born interpretation

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the interpretation of the square of the wavefunction of a particle as the probabillity density for finding the particle in a region of space

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node

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a point or surface on which a wavefunction passes through zero/a place where there is zero chance of an electron

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particle-in-a-box

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a particle confined between rigid walls/explains phenomena in both chemistry and physics

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Schrödingers equation

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the equation for a particle of mass m moving in a region where the potential energy is V(x)/an operation on wave functions--allows us to do operations on a wave

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the energy of a particle-in-a-box equation

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schrödingers equation and the standing wave equation give the equation of a particle as a function of the quantum number n

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standing wave

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a wave stable over time/a wave with peaks and troughs that do not migrate with time

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quantum mechanics

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the description of matter that takes into account the wave-particle duality of matter & the fact that the energy of an object may be changed only in discrete steps

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quantization

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the restriction of a property to certain values
examples:the quantization of energy & angular momentum

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energy levels

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when an electron changes energy levels, energy is absorbed or emitted/an electron jumping up and energy level requires energy absorption/an electron that drops an energy level emits energy

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zero point energy (ZPE)

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says that a particle cannot have zero energy (n=0--ZPE is what u get when an n=1/a particle can never actually be perfectly still

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atomic spectra or line spectra

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the places where certain energies (quanta) have been absorbed/on the atomic spectra, lines get closer as n increases/indicate that the theory of quantization is correct

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bohr frequency condition

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the relation between the change in energy of an atom or molecule & the frequency of radiation emitted or absorbed

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the rydberg equation

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an equation for the frequency (locations) of lines/says if an electron goes up in energy(it jumps from a lower n to a higher n), the frequency is positive & when the frequency is positive, the energy is positive &energy will be absorbed/if an electron goes down an energy level, the frequency is negative--the energy is negative & and energy will be emitted
(v>0 means energy absorption, v<0 means energy emitted & λ can be determined from v)

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Columbic potential

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the potential energy between the proton & electron when you have a proton & electron at distance r

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quantum numbers

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n=principle quantum number/n values range from n=1 to n=infinity--the higher the n value, the farther the electron is from the nucleus & the easier it is for the electron to change energy levels(because the nucleaus has less influence on far away electrons) or to leave the atom/each Ψ has 3 quantum numbers associated with it

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atomic orbitals (AOs)

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a region of space in which there is a high probability of finding an electron in an atom--based on distance (r), longitude(θ) & latitude(Ф)

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ground state (of an atom)

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the state of lowest energy

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aufbau principle

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predicts ground state of atom:
1.electrons fill the lowest energy level & work their way up
2.electrons go into lowest energy subshell first
3.each orbital can hold 2 electrons
4.hund's rule

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hund's rule

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when there is more than one orbital of the same energy, electrons fill one per orbital before pairing

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pauli-exlusion priniciple

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no 2 electrons can have the same QNs/2 electrons in the same orbital (same n,l,and ml balues) have different spin (ms value)