⚠️chem midterm study guide

[[1- states of matter[[

• solid- fixed shape and volume, particles touching, not moving
• ^^liquid- fixed volume, unfixed shape, particles touching and moving a little^^
• %%gas- no fixed volume or shape, particles far apart and moving a lot%%
• @@plasma- no fixed volume or shape, particles far apart and moving a lot@@

]]1- properties of and changes in matter]]

• ==physical property==

• anything you can see without changing the substance

• ex. transparency, boiling point, density, elasticity, malleability, brittleness, melting point

• ==chemical property==

  • you can only see by changing the substance
  • ex. flammability, ability to rust, reactivity with vinegar

• @@physical change@@

  • when the identity of the substance doesn’t change (reversible)
  • ex. shattering, melting, separating (sand from gravel), dissolving, mixing, evaporating

• @@chemical change@@

  • when the identity of the substance changes (irreversible), during a chemical reaction
  • ex. rusting, bleaching, cooking, burning, exploding

• extensive property

  • depends on how much matter there is
  • ex. mass, weight, volume

• %%intensive property%%

  • doesn’t matter how much matter there is
  • ex. color, combustibility, density, melting point, malleability

^^chemical reaction^^

• 5 signs:

  • formation of a gas
  • color change/ emission of light
  • odor change
  • temp change
  • formation of a precipitate

• parts of a reaction

  • reactant, yield arrow, product. the compound on top of the yield arrow is the catalyst- it speeds up the reaction time.

  

Law of conservation of mass: in a closed system, mass cannot be created or destroyed

{{1- elements, compounds, and mixtures{{

Matter is classified into ==Pure Substances== and ^^Mixtures.^^

• ==Pure Substance==- only one type of molecule, ex. water. can be @@elements@@ or compounds.

  • @@element@@- an atom with specific characteristics, ex. hydrogen, iron, copper
  • can be metals or nonmetals, can’t be broken down further
  • compound- a molecule made of different atoms, ex. H2O, Na2
  • can be broken down into molecules using chemical charges
  • can be molecular, ionic, or intermetallic compounds

• ! ! pure substances can’t be broken down by physical means like distillation, filtration, chromatography, or evaporation ! !

• ^^Mixture^^- combo of 2 substances, not chemically bonded. can be %%solutions%% or heterogeneous mixtures. Can be separated through physical changes.

  • %%solution (aka homogenous)%%- a group of molecules that are evenly distributed, ex. gasoline, air, and soda

• heterogeneous mixture- a solution that is unevenly distributed, ex. cereal/ milk, raisin bread

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}}2- precision and accuracy}}

• precision- the extent to which a series of measurements of the same quantity made in the same way agree with each other, not necessarily accurate.
• accuracy- the extent to which a measurement approaches the true value of a quantity

to find percent error: [(experimental - accepted) / accepted] * 100

🔎 look at page #9 in binder

<<2- significant figures<<

any digit in a measurement that is known with certainty, plus one final digit that’s slightly estimated

• rule 1- all nonzero digits are significant, ex. 254 has 3 sigfigs
• rule 2- zeros in between nonzeros are significant, ex. 2001 has 4 sigfigs
• rule 3- trailing zeros are only significant with a decimal after, ex. 2000.0 has 3 sigfigs
• rule 4- zeros in front of a nonzero don’t count, regardless of decimal, ex. 00.0004 has 1 sigfig

rules of rounding

• round up if trailing # is above 5………….. so 4566.89 rounded to 4 sigfigs is 4567
• leave it alone if trailing # is below 5…… so 4564.45 rounded to 4 sigfigs is 4564

for math operations (x / + -)

• always round according to the # with the least amount of decimal places (least accurate)

(10.3) x (0.01345) = 0.138535 → 0.139

🔎 **look at binder page #6,7,8,10 for more examples

\n [[2- scientific notation[[

• used when numbers are super big or super small, like atoms or planets
• numbers are written as a product (multiply) of 2 numbers, a **coefficient

** and 10 raised to a power.4500 →**4.5

• \
• \

** x 10³, coefficient is4.5coefficient must be from 1 - 9.**can’t be 10!!***if the # is greater than 10, exponent is positive and is = to the amount of spaces the decimal is moved left to write the # in scientific notation4.500 → 4.5 x 10³⤴⤴⤴ (move 3 times right, so power of 3)if the # is less than 10, the exponent wll be negative and is = to the amount of spaces the decimal is moved right.00012 → 1.2 x 10⁻⁴12 → 1.2 x 10¹.000,0007 → 7 x 10⁻⁷490 → 4.9 x 10²1000 →1 x 10³.987 → 9.87 x 10-¹1000 000 → 1 x 10⁶0.0375 → 3.75 x 10⁻²0.01 → 1 x 10⁻²596 → 5.96 x 10².001257 → 1.26 x 10⁻³0.000595 → 5.95 x 10⁻⁴]]2- density]]

==mass==**:

• ** theamount of matter an object contains. Doesn’t change unless you add/remove matterfind with a balance, use ==grams==

volume**:

• ** theamount of space an object occupiesfind with liquid or a ruler, use mL for liquids or cm³ for solids or L for gases

@@density@@**:

• \
• \

** thecompactness of the molecules or particles of a substancemore compact molecules = greater densitythe relationship between an object’s mass and volume==mass== **/ volume = @@density@@

• \
  • \
  • \
  • **remember:mL - volumeg - mass

g/mL org/cm³ org/L- density🔎 look at page # 17, 18, 19~~~~{{3- history of the atom{{

scientist/s	experiment/model	year	description/ discovery
Democritus/Dalton- the atom	n/a		**billiards ball-
** small, hard sphereJJ Thompson- electrons	cathode ray tube		**plum pudding-
** electron “plums“ in a positive “pudding“Ernest Rutherford- atom mostly empty space, nucleus, protons on nucleus			**nuclear model-
			** nucleus with electron shellNiehls Bohr- atomic energy levelsBohr’s atomic model**planetary model-
			** electron shell is made of layers/orbitsHeisenberg & Schroedinger- electron cloud and orbitalsHeisenberg uncertainty principle**quantum model-
			** (electron cloud)- there’s certain waves in the cloud?? what??James Chadwick- neutronsquantum model w/ neutrons**modern model-

** discovered neutrons, current model used today🔎 look at page # 29}}3- atomic structure}}

==atom==

• the smallest particle of an element that still has the chemical properties of the element

@@nucleus@@

• very small thing @@in the center@@ of the atom
• made of at least one proton (p+) and usually at least 1 neutron (n*)
• surrounding the nucleus is a cloud of electrons (e-)

protons, neutrons, and electrons are called **Subatomic Particles

protons (p+)**

• located in nucleus, positive charge, big and heavy

%%neutrons (n)*%%

• located in nucleus, %%no%% charge, big and heavy

^^electrons (e-)^^

• outside the nucleus, ^^negative^^ charge, tiny and light

<<3- isotopes and ions<<

==isotopes==

• 2 atoms with different # of ==neutrons==
• \
  # protons never changes
• \
  # neutrons can change
• have the same atomic #, different mass #s

@@ions@@

• an atom with @@a charge@@, # of @@electrons@@ change
• if atom loses electrons, atom is + and (vice versa)
• protons, neutrons, atomic # and atomic mass stay the same

hyphen notation

• (element name) dash (mass number)
• ex. uranium-235

%%isotope notation (nuclear symbol)%%

• top - mass #……….. bottom - atomic #
• ex. %%U²³⁵₉₂%% (pretend like that’s lined up)

nuclide- general term for a specific isotope of an element (probably don’t need to know this)

[[3- atomic #, atomic mass, mass number[[

**atomic #

• \

** = protonsin a neutral atom, protons = electrons**mass #

** = protons + neutrons**atomic mass

** = the decimal in the element box**neutrons

** = mass # - atomic #]]electron configuration]]

periodic table

metals, nonmetals, and metalloids

periodic trends

valence electrons

cations and anions

nomenclature (ionic and molecular compounds; acids)

1. **states of matter
2. ****properties of and changes in matter
3. ****elements, compounds, and mixtures
4. 5.
5. 7.
6. precision and accuracysignificant figuresscientific notationdensityhistory of the atom
7. ****atomic structure
   10. 11.
   11. 13. isotopes and ionsatomic #, atomic mass, mass numberelectron configurationperiodic table
   12. ****metals, nonmetals, and metalloids
   13. ****periodic trends
   14. 17.
   18.