Chem 1 test (103)

Matter

anything that has mass and occupies space

Chemistry

the study of matter

solid

liquid

gas

physical properties

can be observed or measured without trying to change the composition of the matter being studied (color, size, volume)

chemical properties

Demonstrated when attempts are made to change matter into other kinds of matter (acidity, reactivity, flammability)

Physical changes

change matter undergoes without changing composition

Chemical changes

Change matter undergoes that involves changes in composition

Pure substance

has constant composition and fixed properties (water, sugar, salt)

Mixture

A blend of matter that can be physically separated into its separate components (sugar water)

Homogenous matter

matter that has the same properties throughout the sample, they are solutions (uniform)

Heterogenous matter

matter with properties that are not the same though out the sample (non-uniform)

Examples of Homogenous matter

air, milk, soda, IV/saline solutions

Examples of Heterogenous matter

Humans, blood, steak

Elements (pure substance)

"building blocks" consisting of one type of atom in the form of homoatomic molecules or individual atoms (cannot be broken down further with chemical means)

Atoms

The limit of chemical subdivision for matter "building blocks of elements"

Compounds

A pure substance consisting of 2 or more elements with definite composition that can be broken down into simpler substances by chemical methods

molecules

smallest particle of a pure substance that has properties of that substance and is capable of stable independent existence

Diatomic molecules

contains 2 atoms

Homoatomic molecules

contain 1 KIND of atom

triatomic molecules

contains 3 atoms

polyatomic molecules

contains more than three atoms

Heteroatomic molecules

contain 2 or more KINDS of atoms

tera-

10^12

giga-

10^9

mega-

10^6

kilo-

10^3

deci-

10^-1

centi-

10^-2

milli-

10^-3

micro-

10^-6

nano-

10^-9

Scientific notation

Represents numbers consisting of a product between a nonexponential number and 10 raised to a whole number exponent (m x 10^n)

sig figs

The number in a measurement that represents the certainty of the measurement, +1 number representing an estimate

sig fig rule for mult/div

Always use smallest number of sig figs presented in the problem for answer

sig figs for add/sub

use the smallest number of DECIMAL PLACES presented in the problem

Sig fig rules for zeros

leading zeros are non-significant but buried zeros are significant, trailing zeros require a decimal place to be significant

formula for Celsius to Fahrenheit

(9/5)(C)+32 =F

Percentage equation

part/whole x 100

part equation

(percent)(total)/100

Mixed calculation sig fig rule

According to PEMDAS, the last calculation determines the sig fig rule

Density equation

mass/volume

definition of density

physical property of matter

periods

horizontal rows on periodic table (similar electron config)

groups

vertical columns on periodic table (similar characteristics)

Characteristics of metals

high thermal/electrical conductivity, luster, ductile, malleable

Characteristics of non-metals

dull, brittle, poor conductivity

characteristics of metalloids

properties between metals/non-metals

Group 1A

Alkali metals

Group 2A

Alkaline earth metals

Group 7A

Halogens

Group 8A

Nobel gases

Coulomb's Law

Opposites attract, likes repell

Atomic number

shows number of protons

Atomic weight

The mass of the weighted average of the atoms (naturally occurring isotopes) of an element

Isotopes

Atoms that have the same atomic number but different mass numbers (different number of neutrons)

finding atomic weight:

(% isotope)(atomic mass) + (% isotope)(atomic mass)

Radioactive nuclei

nuclei that undergo spontaneous changes and emit energy as radiation (unstable)

Radioisotopes

An isotope of an element that emits nuclear radiation

Radioactive decay

Process in which an unstable nucleus changes energy states and emits radiation in the process

Alpha particles (+)

Identical to helium nucleus and composed of 2 protons and 2 neutrons (most massive, highest charge, don't penetrate paper/skin cells)

Beta particles (-)

Identical to electrons but is produced in the nucleus when a neutron is charged into a proton and an electron (less collisions=more penetrating)

Gamma rays (no charge)

high-energy ray that is like an X ray but with higher energy. Not streams of particles but rays if electromagnetic radiation, very penetrating/dangerous

Nuclear reaction

When 2 atomic nuclei/ an atomic nucleus + another subatomic particle collide, resulting in +1 nuclei

positron

A positively charged electron, antimatter of an electron, penetrates similarly to beta particles (when a nucleus emits a positron, a proton is changed to a neutron, so the daughter nucleus has an atomic number lower by 1)

electron capture

A mode of decay for some unstable nuclei in which an electron from the outside of the nucleus is drawn in where it combines with a proton to make a neutron

Half-life

Time required for one half the unstable nuclei in a sample to undergo radioactive decay

Bohr Model

electrons are confined to clearly defined energy levels spaced at specific distances from the nucleus

atomic orbitals

volume of space around atomic nuclei in which electrons of the same energy may reside at any given time, groups with the same n value form subshells, each orbital can hold 2 electrons

valence electrons

the electrons in the highest period