Chem 101 Exam 1

chemistry

the study of the structure, composition, and properties of matter

empirical scientific knowledge

based on observations and experiments

hypothesis

a tenative interpretation or explanation of observations and is falsifiable (results may support a hypothesis or prove it wrong)

experiment

highly controlled procedures designed to generate observations that confirm or refute a hypothesis

scientific law

a brief statement that describes the behavior of nature and predicts future behavior; doesn’t try to explain the why or how

law of conservation of mass - Lavoisier

in a chemical reaction, matter is not created or destroyed

scientific theory

a model for how and why nature behaves the way it does; can be validated by experiments, but never conclusively proven

atoms

submicroscopic particles that are the building blocks of ordinary matter

matter

anything that occupies space, has measurable mass, and is made up of extremely small particles

molecules

atoms bound together in specific geometric arrangements

sublimation

solid to gas

deposition

gas to solid

molecules

atoms bound together in specific geometric arrangements

crystalline solid

atoms or molecules arranged in patterns with long-range, repeating order

liquid has a…

fixed volume but not fixed shape; assumes shape of container its in

compressible gas

can force the atoms in a smaller space to reduce volume (ex: sitting on an air mattress)

pure substance

made up of only one component and has an invariant composition that doesn’t vary from one sample to another

mixture

composed of 2 or more components in proportions that can vary from one sample to another

element

single type of atom that can’t be broken in simpler substances (ex: oxygen, carbon, helium)

atomic elements

occur in nature as discrete, individual particles

molecular elements

occur in nature as their most stable form glued together (ex: hydrogen(H2), nitrogen(N2), oxygen(O2)

diatomic elements

occur in nature as pairs of two (ex: bromine occurs as Br2)

compounds

substances of two or more in fixed, definite proportions

homogeneous mixtures/solutions

uniform distribution and composition and properties in all regions of the mixture (ex: wet sand)

heterogeneous mixture

have a non-uniform composition varying from one region of the mixture to another; multiple substances whose presence can be seen (ex: chocolate chip cookie dough)

separating heterogeneous mixtures

easier to separate; separation through decanting where you take wet sand and filter water into a separate container

separating homogeneous mixtures

distillation where its boiled so that the more volatile (easily vaporizable) liquid is separated and then recondensed in a condenser and collected in a separate flask

physical changes

changes that alter only the state or appearance, but not the composition (ex: water boiling, cutting, crushing, sugar dissolving)

chemical changes

changes altering the composition of matter; atoms rearrange and transform the original substance into different substances (ex: iron rusting/oxidizing)

physical property

a property that a substance displays without displays without changing its composition (ex: odor, taste, color, density, changes in state of matter)

chemical property

a property a substance displays only by changing its composition via a chemical change; particles change (ex: corrosiveness, acidity, flammability, toxicity)

energy

the capacity to do work, which is the action of a force through a distance; moves in the direction of the force (ex: pushing a box across the floor)

kinetic energy

energy associated with motion (ex: dropping a weight and the resulting acceleration converts potential energy into kinetic)

potential energy

the energy associated w/ position or composition (ex: a weight held above the ground has potential energy due to its position within Earth’s gravitational field)

objects or systems with high potential energy tend to…

be unstable and have a tendency to change in a way that lowers their potential energy

Law of Constant Composition/ Definite Proportions - Joseph Proust

compounds have a constant proportion of elements of elements irrespective of mass; all samples regardless of source have the same proportions of constituent elements

Law of multiple proportions - Dalton

when two elements form two different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers (ex: m oxygen to 1g carbon in CO2/ m oxygen to 1g carbon in CO2 = 2.67/1.33 = 2)

Dalton atomic theory

1. each element is composed of tiny, indestructible particles called atoms

2. all atoms of a given element have the same mass and other properties distinguishing them from atoms of other elements

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

4. atoms of one element do not transmutate into another element via chemical change'; only switch places and always have the same total # of atoms

electron and who discovered it

the electron is a negatively charged, low-mass particle that was discovered by JJ Thomson through cathode ray experiments; the change of an electron was discovered by Millikan’s Oil Drop Experiment

Thomson Plum Pudding Model

believed all the mass of the atom was contained in the electrons that were spread out evenly through a sphere of positive charge

Ernest Rutherford experiemnt

proved the plum pudding model wrong by performing an experiment shooting positively charged alpha particles through a thin sheet of gold foil; expected to go straight through but some of the particles deflected back showing that the electrons can’t be spread evenly throughout the atom

Rutherford Nuclear Theory

1. most of the atom’s mass and all of its positive change is contained in the nucleus

2. most of the volume of the atom in empty space, throughout which tiny negatively charged electrons are dispersed

3. There are as many negatively charged electrons outside the nucleus as there are positively charged protons within the nucleus, so the atom is electrically neutral

neutron and who discovered it

neutrons are particles in the nucleus with similar mass to a proton, but no electrical charge; discovered by James Chadwick to answer why hydrogen (1 proton) is ¼ the mass of helium (2 protons); reason is helium has 2 protons and 2 neutrons while hydrogen has 1 proton and 0 electrons

metals have a tendency to… and non-metals have a tendency to…

loose electrons and form cations and gain electrons and form anions

ionic bond

when oppositely charged ions attract one another by electrostatic forces to form a crystalline lattice of alternating cations and anions

ionic compound

has a metal bonded to a non-metal through ionic bonds; ionic compounds are always charge neutral

formula unit

basic unit of an ionic compound; the smallest, electrically neutral collection of ions

difference between mixtures and compounds

the components of mixtures are not held together by chemical bonds while the atoms of compounds are held together by chemical bonds that form because of the attractions between the protons and electrons of the atoms

molecular compunds

two or more non-metals bonded through covalent bonds; basic unit is a molecule

covalent bonds

two atoms share 1 or more electrons in order to create a molecule with lower potential energy than they do in isolated atoms bc they interact with the nuclei of both atoms

chemical formula

indicates elements present and relative number of atoms or ions; more metallic (+ charged) elements first and less metallic (- charged) elements second

structural formula

uses lines to represent covalent bonds and show how the atoms in a molecule connect or bond to each other

empirical formula

lowest whole number ratio of atoms in an element (HO)

molecular formula

the actual number of atoms in an element (ex: H2O2)

polyatomic molecules

electrically neutral groups or 3 or more atoms held together by covalent bonds (ex: NH4+)

monoatomic molecules

consisting of 1 atom

SI base units (length, mass, time, temperature, amount of substance)

meter (m), kilogram (kg), second (s), kelvin (K), mole (mol)

extensive property

dependent on the amount of a substance (ex: mass and volume)

intensive property

independent of the amount of substance (ex: boiling point)

temperature conversion equations

F = 1.8C + 32

C = (F - 32)/1.8

K = C + 273.15

tera (T)

10^12

giga (G)

10^9

mega (M)

10^6

kilo (k)

10³

deci (d)

(10^-1)

centi ( c )

10^-2

milli (m)

10^-3

micro (u)

10^-6

nano (n)

10^-9

pico (p)

10^-12

1 liter (L) =

1000mL = 1000 cm³

accuracy

closeness to actual

precision

reproducibility; will this produce the same number over and over again

atomic mass

average mass of all isotopes of an element

isotopes

atoms with the same number of protons but a different # of neutrons

atomic number

the number of protons in an atom

mass number

number of protons + number of neutrons

2 isotope notations

mass #/atomic# X (chem.symbol) ; X - mass #

natural abundance

measure of the the average amount of a given isotope on Earth (found by dividing signal intensity of the isotope by the total signal intensity)

ions

atoms with a net charge due to gaining or loosing electrons

cations

positively charged ions from loosing electron(s)

anions

negatively charged ions from gaining electron(s)

1A group charge

+1 cations

2A group charge

+2 cation

3A group charge

+3 cations

5A group charge

-3 anions

group 6A charge

-2 anions

group 7A charge

-1 anions

molar mass

mass of one mole of an atom; numerically equivalent to atomic mass/weight

molecular weight/formula mass

sum of average atomic masses of all atoms in a compound

mass spectrometry

separates isotopes of an element based on mass to charge ratio

metals whose charge is invariant from one compound to another

group 1A and 2A (except for first and last of the groups), scandium, aluminum, zinc, silver (Ag)

metals whose charge varies from one compound to another

transition metals, tin (sn), lead (pb)

nitrate

NO3 -

carbonate

CO3 2-

sulfate

SO4 2-

phosphate

PO4 3-

chlorate

ClO3 -

acetate

C2H3O2 -

Fe

iron