Semester 1 Final

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Chemistry
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The study of matter
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Substance
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a material with a definite chemical composition
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Scientific Law
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a statement that explains what something does in science
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Density/Volume
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Volume and density have derived units. Density which is a ratio of mass to volume, can be used to identify an unknown sample of matter. D=mass/volume
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Kelvin
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To get Kelvin it equals the Celsius temperature plus 273
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Derived/Base Units
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a set of seven base units from which all other units of measurement are formed, by products of the powers of base units: Gram, Liter, Meter, Second, Kelvin
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Scientific Notation
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To add or subtract numbers in scientific notation, must have same exponent
2. To multiply or divide in scientific notation, multiply or divide the coefficients and then add or subtract exponents respectively.
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Dimensional Analysis
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Dimensional analysis uses conversion factors to solve problems
New Unit/Given Unit
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Accuracy
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An accurate measurement is close to the accepted value. A set of precise measurements shows little variation
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Error
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Error is the difference between the measured value and the accepted value.
Error = experimental value – accepted value
Percent error = l error l / accepted value * 100
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Precision
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The number of significant figures reflects the precision of reported data
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Milli-
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1/1000 or 0.001
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Centi-
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1/100 or 0.01
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Kilo-
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1000
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Sig Figs
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1. If decimal is present, start counting from the left at the first non-zero digit.
If not present, start from the right side at the first non-zero digit.
2. +/-: Find the answer, then round to the least significant place of any measurement in the problem
3. x/: Answer has the same number of sig figs as the least sig. # in the problem.
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Isotopes
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Atoms of the same element (same atomic #) but with a different number of neutrons(different mass #
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Isotopic Notation
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Symbolic:
atomic mass
Symbol
Atomic Number

Written Form:
Element–atomic mass

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Bar Graphs
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Shows how a factor varies with time, location, or temperature
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Line graph
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continuous, and can interlope between data
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Physical Property
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can be observed without altering a substance’s composition
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Chemical Property
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a substance’s ability to combine with or change into one or more new substances
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Intensive Property
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Properties that do not depend on the amount of the matter present: Color, Odor, Luster, Malleability, Ductility, Conductivity, Hardness, Melting/Freezing Point, Boiling Point, Density
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Extensive Property
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Properties that do depend on the amount of matter present: Mass, Weight, Volume, Length
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States of Matter
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Gas, Liquid, solid (sometimes vapor)
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Law of Conservation of Mass
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states that mass is neither created nor destroyed during a chemical reaction.
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Solutions
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Homogeneous(same) mixtures
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Mixtures
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-A physical blend of two or more pure substances in any proportion
-Can be separated by physical means.
-Common separation techniques: filtration, distillation, crystallization, sublimation, chromatography
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Law of definite Proportions
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states that a compound is always composed of the same elements in the same proportions
-percent by mass= (mass of the element/mass of the compound)x100
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Law of Multiple Proportions
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states that a chemical compound always contains exactly the same proportion of elements by mass
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Dalton’s Atomic Theory
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Elements are made of extremely small particles called atoms.
Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
Atoms cannot be subdivided, created, or destroyed.
Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
In chemical reactions, atoms are combined, separated, or rearranged
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Atom
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the smallest particle of an element that maintains the properties of that element
-consists mostly of empty space surrounding the nucleus
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Isotopes
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atoms of the same elements with different numbers of neutrons
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Chemical Reactions vs. Nuclear Reactions
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Chemical reactions involve changes in the electrons surrounding an atom. Nuclear reactions involve changes in the nucleus of an atom and conserve atomic # and mass #
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Types of radiation
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Alpha (charge of 2+)
-4 not very penetrating
He low speeds
2
Beta (charge of 1-)
– 0
e
-1
Gamma (no charge or mass)
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1/2 Life
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amount left=original amount(1/2)^n

# of half lives- n=t/T
t=time passed
T= 1/2 life time
n # of 1/2 lives

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Radioisotope
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emit radiation to attain more stable configurations
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Transmutation
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conversion of an atom to an atom of another element by radioactive decay processes- the bombardment of of nuclei with particles (induced transmutation)
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Nuclear Fusion
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the process by which two or more atomic nuclei join together, or “fuse”, to form a single heavier nucleus
-target + projectile=product nucleus + ejected particles
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Nuclear Fission
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refers to either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons (in the form of gamma rays), and releasing a very large amount of energy
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Frequency
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the # of waves that pass a given point per second
-Units: cycle/sec or hertz (Hz or sec^-1)
=v
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Speed of light
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c=3.00 x 10^8 m/s
c=hv
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Light Spectrum
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left= low energy, low frequency, longer wavelength
right= high energy, high frequency, shorter wavelength
-Further the electron drops to the ground state, the higher the energy
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Photons
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Packets of radiant energy
-energy of a photon is proportional to its frequency
E=hr
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Planck’s constant
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6.6262 x 10^-34 Jxs
=h
– Planck= energy emitted or absorbed by an object can only be done in specific, distinct amounts (like a ladder)
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Bohr
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Energy depends on its proximity to nucleus (merry-go-round)
close=low
far= high
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Quantum Mechanical Model
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The atom is found inside a blurry “electron cloud”- an area where there is a high probablility of finding an electron
-assumes that electrons have wave properties
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s sublevel
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# of orbitals: 1
Max electrons:2
Starts at energy level:1
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p sublevel
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# of orbitals: 3
Max electrons:6
Starts at energy level:2
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d sublevel
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# of orbitals:5
Max electrons:10
Starts at energy level:3
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f sublevel
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# of orbitals:7
Max electrons:14
Starts at energy level:4
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Heisenberg uncertainty principle
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a fundamental limit on the accuracy with which certain pairs of physical properties of a particle, such as position and momentum, can be simultaneously known
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Quantum Number
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the energy level of the electron
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Aufbau Principle
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an atom is “built up” by progressively adding electrons. As they are added, they assume their most stable conditions (electron orbitals) with respect to the nucleus and those electrons already there.
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Pauli exclusion principle
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An orbital can hold 0, 1, or 2 electrons only, and if there are two electrons in the orbital, they must have opposite (paired) spins. Therefore, no two electrons in the same atom can have the same set of four Quantum Numbers.
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Hund’s rule
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When filling sublevels other than s, electrons are placed in individual orbitals before they are paired up.
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Periodic law
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when the elements are arranged by increasing atomic number, there is a periodic repetition of their chemical and physical properties.
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Medeleev vs Modern Table
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Mendeleev
ordered by increasing atomic mass, periodicity based on formulas of compounds, other: subgroups, “mixed bag,” graveyards and junkpiles

Modern: ordered by increasing atomic mass, periodicity based on valence electron config, other: actually split (A-s and p/B-d), Metals/metalloids/nonmetals, actinides and lanthanides (f-block)

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Alkali Metal
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Group 1
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Alkaline Earth metals
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Group 2
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Halogens
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Group 7
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Representative Elements
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d elements
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Transition element
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s and p blocks
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Atomic and Ionic Radii
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decrease from left to right, increase as you move down
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Ionization energy
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the energy needed to remove an electron
-generally increases from left to right, decreases as you move down
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Octet rule
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states that atoms gain, lose, or share electrons to acquire a full set of eight valence electrons
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Electronegativity
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attraction an atom has for a shared pair of electrons
-generally increases from left to right, decreases as you move down
-difference determinds bond type
-bigger distance=more ionic
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Cation
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positive, Metal Ions
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Anion
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negative, nonmetal ions
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Ionic Compound
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contain ionic bonds formed by the attraction of oppositely charged ions.
-Ions in an ionic compound are arranged in a repeating pattern known as a crystal lattice.
-Ionic compounds properties are related to ionic bond strength.
-are electrolytes
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electrolytes
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conduct an electric current in the liquid phase and in aqueous solution.
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Metallic Bond
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forms when metal cations attract freely moving, delocalized valence electrons.
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Metal Alloys
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formed when a metal is mixed with one or more other elements
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Covalent bonds
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form when atoms share one or more pairs of electrons
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Resonance
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occurs when more than one valid Lewis structure exists for the same molecule
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Coordinate Covalent Bond/Dipole
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the two electrons derive from the same atom
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VSEPR model theory
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states that electron pairs repel each other and determine both shape of and bond angles in a molecule
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Hybridization
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explains the observed shapes of molecules by the presence of equivalent hybrid orbitals.

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