CHEM I HATE MY LIFE

order of operations scientific method

observation → question → background research → hypothesis → prediction → experiment → analyze data → conclusion → discuss results

confounding variable

factor that isn’t the main variable being studied, can affect outcome of eperiment

experimental group

receives drug

control group

does NOT receive drug

placebo group

eliminates psychological bias

measures of reliability for experimental data

• look for limitation factors

• identify confounding variables

• designed not to be biased

• reproducible results not by chance

Are accuracy and precision interconnected or are they mutually exclusive?

precision helps achieve accuracy bc consistent measurements make it easier to fix errors

physical property

observed without changing identity (gold is yellow)

chemical property

substance ability to undergo chemical change/transformation (wood burn to ash)

intensive property

does NOT depend on amount of substance (color: gold is always yellow)

extensive property

depends on amount of substance (volume :1 L vs 3 L)

what do solids and liquids have in common

• packing: constant contact w/ neighbors

• both are hard to compress

how do solids and liquids differ

• motion: solids vibrate, liquids have all types of motion

• flow: solids don’t flow, liquids flow easily

how are liquids and gases common?

• motion: all types of motion

• packing: particles move past one another

• flow: fills space

how do liquids and gases differ?

• liquids have close particles while gases have lots of space between particles

• gases are highly compressible liquids NO

How is plasma different from a a gas?

plasma

• ionized particles

• conducts electricity

• responsive to electromagnetic fields

• most abundant matter

Which state of matter has the most translational motion?

Gas

Which state of matter has the least translational motion?

solid

constant contact with neighboring particles

solids & liquids

not in contact with other particles

gases & plasma

crystalline solids (diamond, salt, sugar)

• particles highly ordered, repeating pattern

• melting point: definite, specific temp

• rigid, strong

amorphous solids (glass, plastic rubber)

• particles disordered, no repeating pattern

• melting point: not definite, softens over temperatures

• can be flexible, deform, break irregularly

pure substance

• made up of 1 type of molecule

• chemical composition does not change from one to the other

• same properties for all samples

mixture

• 2 or more particles combined

• composition can vary from one to the other

homogenous solution

components uniformly distributed; every sample of mixture has identical properties

heterogeneous solution

non-uniform composition, particles unevenly distributed

miscible

liquids mix together to form one, homogeneous solution

Law of Conservation of Mass

matter is neither created nor destroyed in a chemical reaction;

mass of reactants = mass of products

Law of Definite Proportions

composition of a compound is constant

H2O is always 11% hydeorgen and 89% oxygen

Law of Multiple Proportions

elements can combine in different ratios to form different compounds

carbon and oxygen form carbon monoxide CO (1:1 ratio) and carbon dioxide CO2 (1:2 ratio)

Dalton’s Atomic Theory

1. all matter is made up of invisible atoms

2. all atoms of a given element are identical in mass and properties

3. atoms of elements are unique to that element

4. compounds are formed in fixed ratios

5. atoms rearrange in reaction, conserving mass

Modified Aspects in Dalton’s Theory

1. all matter is made up of invisible atoms (protons, neutrons, electrons)

2. all atoms of a given element are identical in mass and properties (isotopes; same element different number of neutrons)

Valid Aspects in Dalton’s Theory

3. atoms of elements are unique to that element

4. compounds form in fixed ratios

5. atoms rearrange in reactions, conserving mass

Nagaoka’s Saturnian Model of the Atom

atom is like Saturn; large sphere with electrons orbiting around it

what Nagaoka got right

electrons move around a central positive region

what Nagaoka got wrong

• positive charge was not concentrated by tiny nucleus

• no explanation of stability of electron orbits

Thomson’s Plum Pudding Model

atom is a sphere of positive charge with electrons (negative “plums”) spread throughout (raisins in pudding)

what Thomson got right

• discovered the electron

• recognized atoms are divisible into smaller parts

what Thomson got wrong

• positive charge was not spread out (concentrated in a nucleus)

• could not explain scattering

Rutherford’s Nuclear Model

atom is mostly empty space, with a tiny positively charged nucleus at the center orbited by electrons

what Rutherford got right

• discovered nucleus (gold foil experiment)

• most of the atom is empty space

what Rutherford for wrong

• did not explain electron stability

• couldn’t account for atomic spectra

model still accepted today

Rutherford Nuclear Model

element

a pure substance made up of only one type of atom

atom

the smallest unit of an element that retains the element’s chemical identity

ion

an atom or group of atoms with a net electric charge because it gained or lost electrons

isotope

atoms of the same element with the same number of protons but different number of neutrons meaning different masses (Carbon-12 and Carbon-14)

allotrope

different structural forms of the same element (carbon can be diamond or graphite)

molecule

two or more SAME or DIFFERENT atoms bonded together (H2O)

compounds

a pure substance of two or more DIFFERENT ELEMENTS bonded together in fixed ratios (NaCl)