Chem Midterm

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percent error

ratio of an error to an accepted value

alkali metals

group 1A elements (minus H)

chemical

any substance that has a definite composition

chemistry

the study of matter and the changes that it undergoes

chlorofluorocarbon

Man-made chemicals containing chlorine, fluorine, and carbon

conclusion

a judgment based on the information obtained

control

a standard for comparison

hypothesis

A tentative explanation for what has been observed

mass

the amount of matter an object contains

matter

anything that has mass and takes up space.

model

a visual, verbal or mathematical explanation of data collected from many experiments

observation

the act of gathering information

ozone

Three particles of oxygen located in the stratosphere that protect the earth from harmful ultraviolet radiation

qualitative data

information that describes physical characteristics.

quantitative data

numerical information

scientific method

n organized process used by scientists to do research that provides a method for them to verify the work of others

technology

The practical use of scientific information. (ex: nuclear power, artificial limbs)

theory

an explanation that has been supported by many, many experiments.

accuracy

How close a measurement is to an accepted value (or actual value)

base unit

a defined unit based on an object or event in the physical world

conversion factor

a ratio of equivalent values used to express the same quantity in different units

derived unit

a unit that is a combination of base units

dimensional analysis

A method of problem-solving that focuses on the units used to describe matter

graph

a visual representation of information (line, bar, circle)

Kelvin

the base unit for temperature

precision

How close a series of measurements are to one another

second

the base unit for time

significant figure

all the known digits plus one estimated digit

chromatography

based on the tendency of one substance to travel across the surface of a material

compound

a combination of two or more different elements that are combined chemically

chrystallization

making a pure solid drop out of a solution

distillation

based on differences in boiling points

element

cannot be separated into simpler substances

extensive properties

dependent upon the amount of substance present

filtration

a technique that uses a porous barrier to separate a solid from a liquid

heterogeneous mixture

a mixture that does not blend smoothly throughout and the individual substances remain distinct

mixture

a combination of two or more pure substances in which each pure substance retains its individual chemical properties

percent by mass

The ratio of the mass of an element to the total mass of the compound

homogeneous mixture

a mixture that has a constant composition throughout; it always has a single phase

law of conservation of mass

Mass is neither created nor destroyed during a chemical reaction - it is conserved

solid

definite shape & volume, particles vibrate in place, tightly backed together

law of definite proportions

Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass

solution

a uniform mixture that may contain solids, liquids, or gases (also called a homogenous mixture)

law of multiple proportions

When different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other elements in a ratio of small whole numbers

states of matter

the physical forms in which all matter on earth naturally exists (solid, liquid & gas)

liquid

constant volume, take the shape on of the container, particles flow past one another, evenly spaced particles

substance

matter that has a uniform and unchanging composition

vapor

gaseous state of a substance that is a liquid or solid at room temperature

alpha particle

4 protons and 2 neutrons (identical to a Helium nucleus).

alpha radiation

nuclear reaction involving the release of an alpha particle. It is deflected toward a negative source when released between two electrically charged plates

atom

the smallest particle of an element that retains the properties of the element

atomic mass

the weighted average mass of the isotopes of that element

atomic mass unit

the unit used to describe the mass of atoms. It is equal to 1/12 the mass of a carbon-12 atom

beta particle

a high speed electron with a -1 charge released during beta decay

beta radiation

radiation that is made of beta particles. It is deflected toward a positive source when released between two electrically charged plates

nucleus

A tiny, dense positively charged region at the center of the atom

proton

subatomic particle with a mass of 1 amu and charge of +1 located in the atom's nucleus

radiation

rays and particles emitted by the radioactive materials

radioactivity

a process whereby substances spontaneously emit radiation

cathode ray

a negative stream of particles

nuclear equation

a type of equation that shows the atomic number and the mass number of the particles involved,

nuclear reaction

reactions that involve a change in an atom's nucleus.

Dalton's atomic theory

theory that marked the beginning of early atomic theory

electron

negatively charged particles (no mass, charge -1)

gamma ray

high energy radiation that has no electrical charge and no mass, usually accompanies other radioactive particles and accounts for most of the energy lost during decay

isotope

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

mass number

\# protons + # neutrons

neutron

subatomic particle with a mass of 1 amu and charge of 0 located in the atom's nucleus

atomic emission spectrum

set of frequencies of the electromagnetic spectrum emitted by atoms of the element

amplitude

wave's height from origin to crest or origin to trough

atomic orbital

the three-dimensional region around an atom's nucleus that describes the electron's probable location

aufbau principle

states that each electron occupies the lowest energy orbital available

de Broglie equation

lambda = h / mv

electromagnetic radiation

form of energy that exhibits wavelike behavior as it travels through space

electromagnetic spectrum

includes all fors of electromagnetic radiation, with the only differences being the frequency and wavelengths

electron configuration

the arrangement of electrons in an atom

electron dot structure

electron symbol (represents the atomic nucleus and inner-level electrons) surrounded by dots representing valence electrons

energy sublevel

the energy levels contained within a principle energy level

frequency

number of waves that pass a given point per second

ground state

lowest allowable energy state

Heisenberg uncertainty principle

it is impossible to know the precise velocity and position of a particle (electron) at the same time

Hund's rule

states that when equal energy orbitals are available, electrons will enter one at a time. When all orbitals are half-filled, pairing will occur

Pauli exclusion principle

a maximum of 2 electrons can occupy a single atomic orbital

photoelectric effect

the phenomenon in which photoelectrons are emitted from a metal's surface when light of a certain frequency shines on the surface

photon

the particle of electromagnetic radiation with no mass that carries a quantum of energy

principle energy level

the major energy levels of an atom

principle quantum number

n, which the quantum mechanical model assigns to indicate the relative sizes and energies of atomic orbitals

quantum

minimum amount of energy that can be gained or lost by an atom

quantum mechanical model of the atom

an atomic model in which electrons are treated as waves; also called the wave mechanical model of the atom

wavelength

shortest distance between equivalence points on a continuous wave

electronegativity

the relative ability of and atom to attract electrons in a chemical bond.

halogen

group 7A elements

group

the vertical columns in the periodic table.

alkaline earth metal

group 2A elements (reactive elements)

ionization energy

the energy required to remove an electron from a gaseous atom.

ion

atom is bonded group of atoms with a positive or negative charge

metalloid

Elements with physical and chemical properties of both metals and nonmetals (used as semi-conductors)

noble gas

group 8A elements (extremely unreactive elements)

octet rule

atoms tend to gain, lose, or share electrons in order to acquire a full set of eight valence electrons. This gives them a noble gas configuration.

periodic law

the periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number