gen chem mini exam 1

matter

anything that has mass and volume

atoms

can refer to atoms that have lost or gained electrons. can combine to form compounds

molecules

bound atoms, composes a substance determined by atoms

scientific law

statement that summarizes past observations and predicts future ones. describes how nature behaves

law of conservation of mass

in a chemical reaction, matter is neither created nor destroyed. lavoisier

theory

model for the way nature is and explains why and what. validated by experiments but never proven

substance

only made of 1 uniform element, chemically combined. can either be made up of molecules or atoms

3 types of matter

elements (substance), compounds (substance), mixtures (not a substance)

pure substance

only made of one component, its composition doesnt vary. can be individual atoms or groups of atoms joined togerher

elements

cant be broken down into simpler substances

compound

substance composed of two or more elements in fixed proportion, chemically bonded

mixture

2 or more components in proportions that can vary from one another (sweet tea). not chemically combined and can be separated by physical changes. retains many of the properties of the components

solution

aka homogeneous mixture. same composition throughout, uniformly mixed

aqueous solutions

solutions dissolved in water

decanting

pouring off a liquid

distillation

separating a homogeneous mixture (solution) of lliquids. mixture is heated to boil off more volatile liquids

physical changes

changes that alter only state or appearance but not composition. atoms or molecules dont change their identity

physical property

property that a substance displays without changing composition. ex smell of gas, odor, taste, color

chemical change

results in a completely different substance, changes that alter the composition of matter. ex rusting iron combines with oxygen

chemical property

displays only by changing its composition via change. ex corrosiveness, acidity, toxicity. involving chemical reactions, evidenced by temp or color changes. only chemical examinations can determine what type of change it is

energy

the capacity to do work. neither created nor destroyed

work

the action of a force through a distance

total energy

the sum of kinetic and potential energy

thermal energy

a type of kinetic energy because its associated with the motion of individual atoms.

potential energy

often unstable, associated with position or composition. use unstable changes like combustion to lower potential energy and make it more stable

mass v weight

mass is the measure of quantity of matter within an object. weight is the measure of gravitational pull on matter

temperature

measure of average kinetic energy. thermal energy goes from hot to cold objects.

kelvin

absolute zero- the coldest temp possible where molecular motion stops. C + 273.15

how to calculate farenheight from celcius

(c * 1.8) + 32

electric current

ampere, A

luminous intensity

candela, cd

exa

10^18

peta

10^15

tera

10^12

giga

10^9

mega

10^6

kilo

10³

deci

10^-1

centi

10^-2

milli

10^-3

micro

10^-6

nano

10^-9

pico

10^-12

femto

10^-15

atto

10^-18

derived unit

combination of any other units

density

an intensive property

intensive property

property that is independent of the amount of substance

extensive property

ex mass, one that depends on the amount of the substance

exact numbers

unlimited amount of sigfigs

1. from the accurate counting of discrete objects. ex 3 balls

2. from dfined quantities. ex number of cm in 1 m

3. from integral numbers that are part of an equation ex: radius=diameter/2

multi/divis sigfigs

result carries the same number of sigfigs as the factor with the fewest sigfigs

in add or sub sigfigs

same number of decimal places as the quantity with the fewest decimal places

accuracy

how close the measured value is to the actual value

precision

how close a series of measurements are to one another or how reproducible they are

random error

error that has the equal probability of being too high or too low, can average itself out

systematic error

error that tends to be repeatedly too high or too low. can be taken into account through calibration

how to go from L to kg

L to mL to cm³ to g to kg

phlogiston theory

explains combustion because combustible materials contain combustion. air attracts plogiston out of charcoal and stops when it is saturated. disproved by lavoisier, oxygen combines with a substance when it burns and the product weighs more because the mss includes the mass of the oxygen

molecular element

2 of the same thing bonded together

molecular compound

2 things covalently bonded

law of definite proportions

all samples of a given compound, regardless of source, have the same proportions of their constituent elements

how to solve law of definite proprotions

set up a proportion of a to b with the numbers they give you and use dimensional analysis to calculate the new number

atomic theory- dalton

1. each element is made of tiny, indestructible atoms

2. all atoms of a given element have the same mass and other proprties that distinguish them

3. atoms combine in simple, whole number ratios to form compounds

4. atoms of one element cant change into atoms of another. in a chem reaction, atoms only change the way theyre bound together with other atoms

law of multiple proportions- dalton

when two elements from 2 different compounds, the masses of element b that combine with 1 g of element a can be expressed as a ratio of small whole numbers.

cathode rays

discovered that cathode rays carry a negative electrical charge (electrons), which result in electrostatic forces

electric field

area around a charge particle where electrostatic forces exist

millikans oil drop experiment

deduced the charge of a single electron. calculated oil droplets falling in an electric field. helps us find the mass of an electron

how to calculate mass of an electron

charge of electron * mass/charge

mass of electorns

9.109 × 10e -28

plum pudding model- thomson

atom is a sphere of positive charge that has negative electrons in it, like a blueberry muffin. the mass of the atom is contained in the blueberries that are spread evenly throughout the massless dough

rutherfords gold foil experiment

shot particles through gold foil, should blast through. but, some bounced back, showing that the mass of the atom was focused in the nucleus. the rest is empty space with floating electrons in the cloud

nuclear theory

1. most of the atoms mass and all of its positive charge are contained in the nucleus

2. most of the volume is empty space, where electrons are

3. there are electrons and protons, so the atom is electrically neutral. mass is very small and dispersed over a large volume, mostly empty space. matter is much less uniform than we thought

chadwick

finished rutherfords model by discovering neutrons in the nucleus for the unaccounted mass

atomic mass unit

1/12 the mass of a carbon atom that contains 6 protons and 6 neutrons. mass of proton or neutron is approx 1 amu but electrons are much smaller

atomic number

number of protons in the nucleus of an atom. defines the element, the periodic table lists elements in order of increasing atomic number. also the number of electrons in a neutral atom

isotopes

atoms with the same number of protons but different number of neutrons, which just add extra mass. but, the size of an element for all isotopes is the same bc its so small

how are isotopes represented

mass number

protons + neutrons

other way to represent isotopes

chemical symbol-mass. ex Ne-20

periodic law

when elements are arranged in order of increasing mass, certain sets of properties recur periodically and fall into columns

modern periodic table

listed in order of increasing atomic number, not mass

metals

good conductors, can be drawn into wires (ductility), shiny solids, lose electrons

nonmetals

varied properties- can be solids or gases (bromide is the only liquid). poor conductors of heat and electricity. gain electrons

metalloids

mixed properties. semiconductors because of their intermediate electrical conductivity. used in electirc chips aka semimetals

main group elements

properties are predictable based on position in periodic table. labeled with number and A. lose electrons

main group metals

lose electrons, forming a cation with the same number of electrons as the nearest noble gas

nonmetal main group elements

gains electrons, forming anion with same number electrons as nearest noble gas

transition metals

less predictable properties, number and B. contains inner transition elements

inner transition elements

lanthanides and acinides

columns

each column within the main group is a family or group of elements. usually have similar proper

noble gases

8A. unreactive

alkalai metals

1A except for hydrogen. reactive metals

alkaline earth metals

2A, fairly reactive but not ask much as alkalai

halogens

7A, reactive nonmetals

other main groups names

named for first element in the group ex oxygen family

atomic mass

average mass of the isotopes of the element, weighted according to the natural abundance of each isotope.

sum of (fraction of isotope)*(mass of isotope)

mass spectrometry

technique that separates particles according to mass. measures masses of atoms and the percent abundances of isotopes of elements. sample is injected and ionized

how to find total intensity from mass spectrometer results

divide each peak by totl intensity.

ex: 92.9/100+92.9

1 mol

6.022 × 10^(23)