AP chem: unit 1

what is a chemical?

a substance that always has the same composition and properties wherever it is found

what is matter?

anything that takes up space and has mass

what is mass?

the measure of the amount of material in an object (resistance to accelerate)

what is weight?

a measure of the force with which an object is affected by gravity

what is volume?

the amount of space an object occupies in 3D

what are two ways by which volume is measured?

by using a ruler and through displacement

what are the three states of matter?

solid, liquid, and gas

what is the arrangement of a solid?

definite shape and volume

what is the arrangement of a liquid?

no definite shape but has volume

what is the arrangement of a gas?

no definite shape or volume

what is a physical change?

changes in matter that do not change the identity/composition of a substance

what type of change is a phase change?

a physical change

what is a chemical change?

changes that result in new substances with their own set of properties

what are some examples of chemical changes?

combustion, oxidation, decomposition

can atoms be broken down through chemical changes?

no

what are diatomic molecules?

consist of two atoms, which can be the same or different

what are monoatomic molecules?

consist of a single atom

what are polyatomic molecules?

consist of more than two atoms

what are the 7 diatomic elements?

H2, O2, F2, Br2, I2, N2, Cl2

what does a compound consist of?

molecules or ions of two or more different atoms

what is a pure substance?

matter that consists of just one type of atom or one type of molecule

what are mixtures?

two or more substances that are physically mixed together

how do you separate a mixture and why this particular method?

through physical changes because mixtures are not bonded chemically

what is a homogenous mixture?

a mixture in which the compounds are uniformly distributed

what is a heterogeneous mixture?

a mixture in which components are not uniformly distributed

how do mixtures and compounds differ in terms of combination and separation?

compounds are chemically combined/separated, while mixtures are physically combined/separated

how do mixtures and compounds differ in terms of their constituents' properties?

in a mixture, each constituent retains its properties (think sweet & sour sauce), while compounds have different properties that are different from its constituents

how do mixtures and compounds differ in terms of their constituents' proportions?

in a compound, elements are combined in a definite ratio, while you can combine substances in any ratio/proportion in a mixture

what is the law of conservation of mass (LoCoM)?

matter cannot be created nor destroyed during a chemical reaction; an equal amount of matter exists before and after an experiment

what is distillation?

a process used to separate a mixture based on differences in boiling points

when might you use distillation?

when you need to separate components of a liquid mixture based on differences in boiling points

what is filtration?

the process of separating a mixture of a solid and liquid

what is chromatography?

a process by which the components of a mixture separate as they move at different rates up the surface of a piece of paper

what is the separation of components of a mixture in chromatography due to?

the differences in solubility in a solvent

what type of substance is closer to the solvent front in chromatography and why?

nonpolar substances because nonpolar substances have a greater affinity for the solvent

what does the solvent front represent in chromatography?

the furthest point reached by the solvent on the chromatographic paper

how is a chromatography experiment set up?

a sample is placed on the chromatography paper and is marked at the baseline; the paper is then suspended in a solvent

what are the most common signs that a chemical reaction has occurred?

color change, formation of a gas (bubbling/fizzing), formation of a precipitate, temperature change, or production of light

if a white solid forms when two clear solutions are mixed, what type of reaction likely occurred?

a precipitation reaction

what does bubbling indicate during a reaction?

a gas is being produced

what does a color change in solution usually suggest?

a change in the oxidation state of a metal ion or the formation of a new compound with different light absorption

how can you tell if water was removed from a hydrate?

mass decreases after heating

what is the international system/SI system?

a system of measurement

what are the two types of SI units?

base units and derived units

what are derived SI units?

composed of two or more base units. properties of matter that are calculated have derived SI units.

what is density?

property of matter that describes how closely packed together the particles of a substance are

what is temperature?

a measure of the average kinetic energy of the particles in a sample. it determines the direction of heat flow

what is the freezing point of water? (ºC)

0ºC

what is the boiling point of water? (ºC)

100ºC

what does a large number of decimal places mean?

there's increased precision and thus less uncertainty

what is precision?

refers to the exactness of a measurement; whether you're able to produce the same value again or not

what is accuracy?

refers to the proximity of a measurement to the true value of a quantity (if known)

a zero is a significant figure if it is….

between nonzero digits or at the end of a decimal point

a zero is not significant if it is….

at the beginning of a decimal number or used as a placeholder in a large number

how many significant figures does an exact number have?

infinitely many

what are some examples of an exact number?

counted quantities, defined numbers, numbers in equations

how do significant figures operate under multiplication/division?

the final answer has the same number of SF's as the measurement with the fewest SF's

how do significant figures operate under addition/subtraction?

the final answer has the same number of decimal places as the measurement having the fewest decimal places

what's the formula for percent error?

|experimental-accepted value| ÷ accepted value • 100

what does it mean if your percent error is negative?

you underestimated

what does it mean if your percent error is positive?

you overestimated

what is a mole/avogrado’s nu?

a set of 6.022*10^23 particles

what is molar mass?

the mass in grams of 1 mole of substance (g/mol)

where are electrons located?

in the space surrounding the nucleus (nucleons)

where are protons located?

in the nucleus

where are neutrons located?

in the nucleus

what is the charge of an electron?

-1

what is the charge of a proton?

+1

what is the charge of a neutron?

0

what does most of the volume of an atom consist of?

empty space

where does most of the mass in an atom come from?

the nucleus

the charge of an atom is

overall neutral, as the number of protons and electrons are equal

what do all atoms of the same element have the same number of?

protons

what is mass number?

the total number of protons and neutrons in the nucleus of one atom (total # of nucleons)

what is an isotope?

atoms of the same element that have different atomic masses

what's the formula for weighted average?

atomic mass = [(mass of isotope1)(%)+(mass of isotope2)(%)+…]/100

what is the law of definite proportions?

a given compound always contains exactly the same proportions of elements of mass

what were the three types of radioactivity discovered by Ernest Rutherford?

(alpha) a particles, (beta) ß particles, (gamma) γ particles

what is an alpha (a) particle?

the heaviest type of radioactivity with a positive charge

what is a beta (ß) particle?

a type of radioactivity with negative charge and negligible mass

what is a gamma (γ) particle?

pure energy

what is an electric field?

the electric force per unit charge

what are electromagnetic waves?

a form of energy that travels through space at the speed of light in a vacuum

what is wavelength (λ)?

the distance between two successive peaks or troughs

what is the trough?

the lowest point of an electromagnetic wave

what is the crest?

the peak of an electromagnetic wave

what is frequency (v)?

the number of wavelengths per second that pass through a given point

which units are used to measure frequency?

hertz (Hz) or cycles per second (s⁻¹)

which units are used to measure wavelength?

nanometers (nm)

what do moving particles produce?

electromagnetic fields

what is the relationship between frequency and wavelength?

an inverse relationship

what is velocity?

the rate at which an object changes its position

what is the 1900 quantum theory?

energy is not absorbed nor released continuously

what was the failure of the Rutherford model?

an accelerating electron should radiate a continuous electromagnetic waves and spiral into the nucleus as it loses energy

what is the continuous spectrum?

contains all wavelengths of visible light (all the colors of the rainbow without any black spots)

what does Beer's law dictate?

absorbance is directly proportional to concentration

what is Beer's law?

A = εbc

what does it mean if a solution is colorless in terms of spectrophotometry?

it doesn't absorb visible light and spectrophotometry cannot be used

why should the maximum wavelength be used in spectrophotometry?

a small change in concentration causes a bigger change in absorbance, making measurements more accurate and precise

what were the conclusions of the gold foil experiment?

atoms mostly consist of empty space but contain a small, heavy, positively charged nucleus