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Independent variable
Variable that stands alone and isn't changed by any other variables
Dependent variable
variable that depends on other factors
% error
how far off from the actual value we are (is always positive)
Accepted value
mutual conclusion that is agreed to be correct after many experiments
Measured or Observed value
value that is measured while observing during the experiment
Density
the amount of matter contained in a given volume
- temperature dependent because substances change volume when heated or cooled
Sig figs or digits (rounding)
- all non-zeros are significant
- leading zeros are never significant
- sandwich zeros are always significant
- trailing zeros are only significant if the decimal is present
Atlantic:
If decimal is absent start on the left side of #, come to the first non-zero count that digit and every digit after
Pacific:
decimal present start on the right side of #, come to the first non-zero count that digit and every digit after
- round answer to contain same # of decimal places, least # of decimal places (add and subtract)
- round answer to contain same # of sigfigs as measurement with least #of sigfigs (multiply and divide)
Measurements
- all measurements must be the same decimal place
- all measurements must include a guess digit
Lab equipment
tools used in lab
Lab safety
hair up, no loose clothing, goggles, tilt tube away from face, gloves or apron if needed
- fire extinguisher, fire blanket, first aid kit, eyewash, and shower.
Hottest part of the bunsen burner
center where the flame is the most present
Heating glassware
on the bottom without a cover
Formula for % error
((Estimated value-Actual value)/Actual value)x100
Example.) ((18-20)/20)x100= 10%
energy
the amount of energy transferred
temperature
measurement that shows the average kinetic energy of a sample
- higher temp more kinetic energy
kinetic energy
energy of motion
- light, sounds (wind), radiant, and electrical
potential energy
stored energy
- chemical, nuclear
law of conservation of energy
energy is not created or destroyed it is only rearranged
kelvin scale
Celsius value+ 273 degrees
absolute zero
0 K/ 273 C
matter
something that takes up space that has mass and volume
physical change/property
same substance, different form
ex: crushing, melting, dissolving, volume, density, mass, pH, boiling point, freezing point
chemical change/property
change that forms a new substance and chemical reaction
law of conservation of matter
neither created nor destroyed, so we must have the same number and type of atoms after the chemical change as were present before the chemical change
element
Simplest form of matter that cannot be broken down. It consists of atoms that have the same atomic number
compound
2 or more elements chemically combined and can only be broken down by chemical means
pure substance
A substance with constant composition
(Elements or compounds)
mixture
Two or more pure substances that are physically combined; can be separated by physical means
heterogeneous mixture
A mixture that doesn't have uniform composition
Ex) Italian salad dressing
homogeneous mixture (aqueous solution)
A mixture that has uniform composition
Ex) Air
endothermic reaction
Heat is absorbed (feels cold); heat is a reactant
exothermic reaction
Heat is released (feels warm); heat is a product
heat flow
hot to cold
melting and boiling point
100 celcius and 32 fahrenheit
filtration
Filtrate flows through filter paper
distillation
Separates two or more liquids with different boiling points
Watch Glass Evaporation
Separates solutes
chromatography
Separates particles based on size and solubility
solid
has a shape
-rigid fixed position, regular pattern
- vibrating
-definite volume
liquid
no definite shape, takes shape of container
- definite volume
gas
no definite shape
no definite volume
- expands to fill container
atom
the basic unit of a chemical element
- charge determined by the number of electrons and protons
cathode ray
a beam of electrons emitted from the cathode of a high-vacuum tube
electron
a negatively charged particle
nucleus
positively charged central core of an atom
proton
positively charged subatomic particle
neutron
neutrally charged subatomic particle
atomic number
the number of protons in the nucleus of an atom
ion
charged particle
positive or negative
isotope
each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons
mass number
the number of protons and neutrons in the nucleus of an atom
atomic mass
weighted average of all the naturally occurring isotopes based on % abundance
- 1/12 mass of carbon-12
line spectrum
an emission spectrum consisting of separate isolated lines (different pH)
quantum number
a number that occurs in the theoretical expression for the value of some quantized property of a subatomic particle
ground state
the lowest energy state of an atom or other particle
- the normal state
excited state
state in which an atom or molecule picks up outside energy, causing an electron to move into a higher-energy orbital
wave-mechanical model
Electrons have distinct amounts of energy and move in areas called orbitals
orbital
region of space where electrons have a high probably of being located
principle energy level
n=1
s(2), p(6), d(10), f(14)
electron configuration
distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals
J.J. Thomson
plum pudding model
- atoms contain electrons
- atoms contain an equal amount of protons and neutrons
Rutherford
gold foil experiment
- conclusion the atom has a positively charged nucleus due to to the repelled particles during the experiment
nuclear atoms:
- mostly empty space
- atoms contain small dense positive nucleus
- electrons are located outside of the nucleus
Bohr model
- small dense positive nucleus
- electrons found in energy levels
quantum mechanical model or Wave- mechanical model
- electrons are found in atomic orbitals (electron clouds)
- small dense positive nucleus
James Chadwick
discovered the neutron
Dalton
- all atoms of the same element are identical, atom dog different elements are different
- atoms cannot be created or destroyed
- atoms combine in different whole number ratios to form compounds
- in a chemical reaction atoms are rearranged
BILLIARD BALL MODEL
Transmutation
One element changed into an atom of another
Natural:
- spontaneous/ naturally occurring
Artificial:
- forceful process/ does not naturally occur
Alpha radiation
- attracted to negative
- atomic number goes down by 1/ mass # goes down by 4
- blocked by a piece of paper or clothing
Beta radiation
- atom emits electron form nucleus
- neutron to proton
- blocked by tinfoil or aluminum foil
- attracted to positive
fission
splitting of a heavy nucleus into light nuclei
fusion
combining of light nuclei to form heavier ones
- requires high temp
Half- life
time it takes for half of a radioactive sample to decay
- shorter the half life, more unstable the isotope is
Radioactivity
- emission of radiation stops when the isotope is stable
- particles which are emitted from nuclei as a result of nuclear instability
- atoms #83 and higher are not stable isotopes
gamma radiation
- does not change composition of the nucleus
- blocked by vest/ concrete singer blocks
- greatest penetrating power
- no mass or charge (particles)
Period law (Mendeleev)
chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights
group
how the energy levels are separated
- metals, transition metals, non-metals
family
down a column
- same # of valence electrons
- increasing number of energy levels
- more shielding
period
across the periodic table
- increasing # of valence electrons
- same number of energy levels
alkali metals
group 1
alkaline earth metals
group 2
halogen
group 17
noble gases
group 18
metals
- good conductors of electricity
- high boiling and melting points
- malleable
- ductile
- solid
- cations (positive- lose electrons)
non metals
- poor conductors of electricity
- low boiling and melting points
- soft
- anions (negative- gain electrons)
semimetals/ metalloids
contains properties of metals and nonmetals
valence electrons
- highest energy level
- most energy
- furthest to the right on the periodic table
periodic trend
lectronegativity, ionization energy, electron affinity, atomic radius, melting point, and metallic character
electronegativity
the measure of elements attraction for electrons when bonded to another atom
- increases going up? and across the periodic table
atomic radius
covalent radius- half the distance between the nuclei and 2 bonded atoms
ionic radius
metals- cations (positive, lose electrons)
nonmetals- anions (negative, gain electrons)
ionization energy
energy required to remove an electron form a neutral atom
isoelectronic
ions of different elements that have the same number of electrons
- same electron configuration
- different radius
Allotropes
each of two or more different physical forms in which an element can exist. Graphite, charcoal, and diamond are all allotropes of carbon
Ionic bond
transfer of electrons
- electronegativity difference greater than 1.7
- reaction between metals and nonmetals
- reacting to achieve the octet rule
covalent bond
2 atoms share electrons in order to achieve stable arrangement
- also called molecular
Non-polar:
2 atoms have an equal sharing of electrons
- electronegativity difference less than .4
Polar:
2 atoms have an unequal sharing of electrons
- electronegativity difference between .4-1.7
- the greater the difference in electronegativity the more polar (ionic) a bond is
ionic compound
sharing of a nonmetal and metal elements with brackets and visible lose and gain of electrons
octet rule
achieving 8 valence electrons
molecule
- smallest unit of a covalent substance
- ionic compounds are not considered molecules
molecular substance
two or more atoms are bonded together with covalent bonds
(special bond)
-covalent
lewis structure
between ions
- ionic and covalent compounds have different lewis dot diagrams since how bonds form are different
