Chem Unit 1 Flashcards
Define element:
Pure substance, simplest form of matter that cannot be broken down further
Define compound:
Pure substance made of two or more elements; cannot be separated physically
Three properties of mixtures:
- No fixed ratio of components
- No fixed boiling point
- Can be separated physically
- Parts maintain their individual properties
One example and definition of homogenous mixtures:
Steel/salt water
- No visible boundaries
- Equal and even distribution of parts
One example and definition of heterogenous mixtures:
Oil and water/carbonated water/cereal
- Clearly defined boundaries
Name of what ends up in the beaker? Name of what ends up in the funnel?
Conditions and steps of filtration:
Non-soluble solid AND solvent
- Pour mixture into filter paper fitted into a funnel
- Solvent goes through pores into beaker at bottom (filtrate)
- Solid remains in filter paper (residue)
Conditions and steps of evaporation:
Soluble solid AND solvent
- Heat solution in evaporation dish
- Solvent is released as vapour
- Solute remains
Conditions and steps of solvation:
Soluble solid AND insoluble solid
- Dissolve soluble solid in solvent
- Filter out insoluble solid
- Evaporate mixture to return soluble solid
Conditions and steps of distillation:
Two liquids with different boiling points
- Heat mixture in beaker
- Liquid with lower boiling point evaporates and travels through condenser
- Condenser turns gas back into liquid to be collected in second beaker
Conditions and steps of paper chromatography:
Mixture of solutes
- Dissolve mixture in solvent (mobile phase)
- Place chromatography paper in solution
- More soluble = travels further up paper; less soluble = travels less
Conditions and steps of recrystallization:
Impure solid
- Place mixture into hot solvent and dissolve
- Filter out impurities
- Slowly cool solid back down, forming pure crystals and leaving impurities in the solution
Equipment required for filtration:
Funnel, filter paper, two beakers, stand
Equipment required for evaporation:
Heat source, evaporation dish, gauze
Equipment required for distillation:
Distillation apparatus (flask, condenser), heat source, two beakers, thermometer
Define allotrope with example:
Alternative form of an elemental substance: e.g. carbon as diamond
The four principles of kinetic molecular theory:
- All matter is made of particles
- Particles are always in motion
- Particles move more at higher temperatures
- Particles do not lose kinetic energy on collision
Two properties of solids:
- Fixed shape
- Fixed volume
- Cannot be compressed
- Cannot flow
Two properties of liquids:
- Variable shape
- Fixed volume
- Cannot be compressed
- Weaker attraction between particles
Two properties of gases:
- Variable shape
- Variable volume
- Can be compressed
- Weakest attraction between particles
Two less-conventional states of matter:
- Plasma
- Liquid crystal
- Bose-Einstein condensate
- Neutron-degenerate matter
Compare and contrast Kelvin and Celsius:
- Kelvin starts at 0K/Celsius “starts” at -273.15
- Kelvin does not use degrees
- One unit of either temperature is proportional to the other
Define and provide one example of an endothermic state change
State change that requires heat to be taken in
Melting, evaporating, sublimating
Define and provide one example for an exothermic state change
State change that requires heat to be emitted
Freezing, condensing, depositing
Formula for kinetic energy
Ek = 1/2 * mass * velocity^2
Latent heat of fusion? For water?
Amount of energy required to change from a solid to liquid; 6.8x less than vaporization
Latent heat of vaporization? For water?
Amount of energy required to change from a liquid to a gas; 6.8x more than fusion
Brief description of Maxwell-Boltzmann distribution and how it changes with temperature?
Graph of energy vs # of gas particles. Most particles meet around a median peak, with less being far away from the peak.
Increases in temperature cause the peak to move right and lower.
Atoms are composed of?
Proton, neutron, electron.
Protons and neutrons collectively are referred to as…
Nucleons; nucleus
Relative masses of protons, neutrons, and electrons?
1, 1, 1/2000
Define isotope:
Atoms with the same atomic number (# of protons) but different atomic masses (# of neutrons)
As mass number of an isotope increases, __ increases
Boiling point, density, and melting point
Briefly explain the mass spectrometer:
I V I A D D
Instrument utilizing the mass-to-charge ratio of a sample of ions to determine percent abundance of isotopes.
Injection, vaporization, ionization, acceleration, deflection, detection
Define radioisotope:
An unstable nuclear arrangement that results in spontaneous decay, emitting nuclear radiation and producing two or more smaller nuclei
Two properties of the radioactive alpha particle:
- Same structure as the nucleus of a He-4 atom, with a 2+ charge
- Large
- Can be blocked by paper
What is it?
Two properties of the beta particle:
- Negatively charged electron
- Passes through paper, but is blocked by aluminum foil
Two properties of the gamma ray:
- High-energy electromagnetic radiation
- Moves at the speed of light
- Penetrates most substances but is blocked by thick sheets of lead
Two applications of radiation?
- Carbon dating
- Medical diagnosis
- Food sterilization
- Energy
One atomic mass unit (amu) is equal to:
1/12 of a carbon-12 atom
Define spectroscopy:
Study of the relationship between matter and electromagnetic interaction
Relationship between frequency and wavelength in energy transitions? Energy and frequency?
- Inversely proportional
- Proportional
As energy levels increase, the space between levels:
gets smaller, i.e. converges
Briefly describe the hydrogen emission spectrum:
Electrons falling from energy levels higher to n = 1 emit UV radiation, from higher to n = 2 emit visible light, from higher to n = 3 emit infrared radiation.
Energy level n = infinity means:
That the electron has been removed from attraction to the nucleus
Explain the emission line spectrum:
If electrons absorb energy, they move up energy levels (unstable relative to ground state) and emit equivalent energy to move back down. Corresponds to the wavelength of visible light released, which in turn shows the emission line spectrum.
Quantum number n represents:
The principal quantum number, i.e. the energy level
Quantum number l represents:
The secondary quantum number; angular momentum quantum number; i.e. the subshell divisions of n
Valid values of n?
1 -> infinity
Valid values of l:
0 -> (n-1)
Letter codes of l are? How many electrons in each?
- s, p, d, f, g…
- 2, 6, 10, 14, 18…
Quantum number m(l) represents:
The magnetic quantum number, i.e. the individual orbitals within the subshells
Valid values of m(l):
- l -> +l
Quantum number m(s) represents:
The spin quantum number, i.e. the direction in which an electron in an orbital spins
Valid values of m(s):
-1/2, 1/2
State the Aufbau principle.
Electron orbitals are filled up from lowest energy level up, i.e. building up.
State Hund’s rule.
In the case of degenerate orbitals (i.e. with the same energy level), each orbital is filled with a single electron before doubling up.
State the Pauli exclusion principle.
No two electrons may have the same quantum numbers; therefore each orbital may only have two electrons spinning oppositely
From left to right on the periodic table, with the lanthanides/actinides last, name the quantum “blocks” of the periodic table:
s -> d -> p -> f
Name four exceptions to the Aufbau principle and why they are exceptions:
- Copper
- Chromium
- Molybdenum
- Silver
Copper and silver move a 4s electron to the 3d orbital for a complete 3d shell. Chromium and molybdenum movie a 4s electron to the 3d orbital for a half-full 3d shell.
Why might an element be multivalent?
For the sake of stability - lose or gain electrons to become a noble gas, or get rid of s electrons (less stable)
Shape of an s orbital?
Spherical
Shape of a p orbital?
“peanut” shaped, along the x, y, and z axes respectively
What is the absorption spectrum? How does it compare to the emission spectrum?
The absorption spectrum is the energy absorbed by the electron when it gains energy. It will overlap perfectly with the emission spectrum.
Briefly state Democritus’s contribution to the atomic model.
Proposed the original model of the indivisible atom (atomos)
Who proposed the original model of the indivisible atom?
Democritus
Briefly state Dalton’s contribution to the atomic model.
Proposed the billiard ball model of the atom - no nucleus or electrons
Who proposed the plum pudding model of the atom?
J. J. Thomson
Who discovered the nucleus via the gold foil experiment?
Ernest Rutherford
Who proposed the billiard ball model of the atom?
John Dalton
Who proposed that electrons act as waves around the nucleus in certain orbitals?
Erwin Schrodinger
Briefly state Thomson’s contribution to the atomic model.
Proposed the plum pudding model of the atom - discovery of the electron
Who predicted the wave/particle duality nature of electrons?
Louis DeBroglie
Briefly state Rutherford’s contribution to the atomic model.
Demonstrated that atoms are mostly empty space, discovering the nucleus (gold foil experiment)
Who proposed that matter was quantized?
Max Planck
Briefly state Bohr’s contribution to the atomic model.
The Bohr Theory states:
Electrons can only exist in fixed orbits or energy levels.
These energy levels are at specific distances from the nucleus.
Any energy emitted/absorbed from/by an atom will be the result of an electron jumping from one energy level to another.
Briefly state Schrodinger’s contribution to the atomic model.
Proposed that electrons act as waves around the nucleus - can only narrow down the regions (orbitals) where an electron is likely to be found
Who made the discovery of the neutron?
James Chadwick
Briefly state DeBroglie’s contribution to the atomic model.
Predicted the wave/particle duality nature of electrons
Briefly state Bohr’s contribution to the quantum atomic model.
Noted the behaviour of hydrogen atoms and predicted the hydrogen emission spectrum/energy levels of electrons
Briefly state Planck’s contribution to the atomic model.
Proposed that matter was quantized, i.e. that a physical quantity can only have certain discrete quantities (for example, you cannot have a population of 13.5 people)
Who conducted the double slit experiment?
Thomas Young
Briefly explain how the double slit experiment worked and what it showed.
Photons are shot through two slits, creating a wave interference pattern.
If one slit is blocked, photons gather like particles would in one area.
If photons are sent one at a time, with time in between, the wave interference pattern appears.
When trying to determine which photon went through which slit, the wave pattern disappears.
What are two possible theories for the double slit experiment’s results?
- Multiverse theory - photons go certain ways in our universe and different ways in another universe
- A “master wave” controls the path that the photon takes
When adding or subtracting, what are the sigdig rules?
Number of decimals must be equal to the number in the limiting term
When multiplying or dividing, what are the sigdig rules?
Number of sigdigs must be equal to the number in the limiting term
How to calculate average atomic mass (in amu)?
- Take the percent abundance of the element (e.g. 30% C-14, 70% C-12)
- Take the weighted average of the percent abundances (e.g. 0.30(14) + 0.70(12))
How to calculate percent abundance?
- Determine the average atomic mass of the element and the major isotopes of the element.
- Set each isotope in terms of x (e.g. 207 = 206(1-2x) + 207(x) + 208(x).)
- Solve for x.
Energy level diagram vs. orbital diagram?
Energy level diagram shows increasing energy upwards (1s -> 2s -> 2p -> 3s -> 3p -> 4s -> 3d -> etc)
Orbital diagram flattens the diagram.
How to find total number of ions in one mole of a compound?
Count the number of ions (eg Mg(NO3)2 has 3 ions). Multiply by Avogadro’s constant.
