Chemistry - Midterm 1

isotope

versions of a particular element that have different numbers of neutrons

ion

atoms (or molecules) that have lost or gained electrons and have an electrical charge

density formula

d = m/v

moles formula with mass

moles = mass / molar mass

moles formula with atoms/particles

moles = (atoms/particles) / avogadros number

avogadros number = 6.022 × 10²³

element

a pure substance made of only one type of atom.

Examples:

• Gold (Au), Oxygen (O₂), Iron (Fe),

• (titanium metal, a substance containing only titanium atoms)

• (fluorine gas, a substance that contains only fluorine atoms)

compound

a pure substance made of two or more elements chemically bonded in a fixed ratio.

Examples:

• Water (H₂O), Salt (NaCl), Carbon dioxide (CO₂).

• phosphorus trichloride, a substance containing phosphorus and chlorine atoms in a fixed 1:3 ratio

• carbon monoxide, a substance containing carbon and oxygen atoms in a fixed 1:1 ratio

homogeneous mixture

A uniform blend where components are evenly mixed (not chemically bonded).

• Key Points:

  • Looks the same throughout (no visible parts).

  • Can be separated by physical methods (e.g., evaporation, distillation).

Examples:

• Saltwater, Air

• an alloy of copper and zinc

• Earth’s atmosphere, which contains 78% nitrogen, 21% oxygen, and small amounts of other gases

heterogeneous mixture

a non-uniform mix where components remain distinct.

• Key Points:

  • You can see the different parts (e.g., oil floating on water).

  • Easily separated by physical means (e.g., filtering, hand-picking).

  Examples:

  • Salad dressing, Sand + iron filings, Granite

intensive property

properties that DO NOT DEPEND on the amount of matter

Examples:

• boiling point

• color

• temperature

• hardness

note: Density is an intensive property. Whether you have a small or large sample, the density of a given material will remain the same. 

extensive property

properties that DO DEPEND on the amount of matter

Examples:

• volume

• mass

• size

• weight

• length

chemical change (in a diagram)

a process where substances transform into new substances with different chemical properties

ex: Splitting a diatomic molecule, requires breaking chemical bonds, which is a chemical change

the relationship between energy, frequency, wavelength, and planck’s constant ((formulas))

e = hv

e = hc / λ ( this is also the formula for a single photon)

h = 6.626 × 10^-34 (planck’s constant)

c = 3.00 × 10⁸ (speed of light)

λ = wavelength

e = energy

ionic bond

transfer of electrons between atoms

covalent bond

sharing of electrons between atoms

chemical bond

the force that holds atoms together to create compounds and molecules

alkane

hydrocarbon containing only carbon-carbon SINGLE bonds

alkene

hydrocarbon containing one carbon-carbon DOUBLE bond

alkyne

a hydrocarbon containing one carbon-carbon TRIPLE bond

resonance structures

when more than one valid Lewis structure can be drawn for a molecule or ion

• resonance structures are always the averages of all the structures

ionic solid

metal + nonmetal or contains polyatomic ions

metallic solid

contains metal only

network covalent solid

diamond, graphite, SiO2, SiC, Si, Ge

molecular covalent

nonmetal + nonmetal that is NOT network covalent