Chemistry Exam 1

The scientific method begins with…

an observation

Scientific method order

Observation, collect data,s hypothesis, experiment

Independent variable

what the experimenter changes

Dependent variable

the effect you measure

control variables

constant

A theory is…

a proposed explanation for a natural phenomenon

serendipity

scientific discovery by accident

chemistry

study of matter and its transformations

transformations of matter involve…

changes in energy

atoms

building blocks of matter

element

made of the same kind of atom

compound

made of two or more different kinds of elements

Fe

Iron

K

Potassium

Ti

Titanium

S

sulfur

U

Uranium

Sn

Tin

Au

Gold

Compounds have

defined ratios of atoms

CaCl2

calcium chloride

CO2

Carbon dioxide

HCl

Hydrochloric acid

Physical changes

changes in matter that do not change the composition of a substance

Chemical changes

Changes that result in new substances

Physical Properties

Can be observed without changing a substance into another substance

Chemical properties

Can only be observed when a substance is changed into another substance

Intensive properties

Independent of the amount of the substance that is present

Extensive properties

Dependent on the amount (extent) of the substance present

Heterogeneous mixture

granite

Homogeneous mixture

bronze

Filtration

separates solids from liquids

Distillation

separates liquids based on differences in boiling points

Chromatography

differences in how dissolved substances adhere to or move through solids

Unit for mass

kilogram

Unit for length

meter

Unit for time

second

unit for temperature

kelvin

amount of substance

mole

unit for volume

Liter, milliliter, or microliters

density

D= m/v

F to C equation

C= (5/9) (f-32)

Zero on the Kelvin scale is

based on the coldest possible temperature

C to K equation

k= c +273.15

Accuracy

the proximity of a measurement to the true value of a quantity

Precision

the proximity of several measurements to each other

Significant Figures rules

1. All nonzero digits are significant
2. Zeroes between two significant figures are themselves significant
3. Zeroes at the beginning of a number are never significant
4. Zeroes at the end of a number are significant only if a decimal point is written in that number

Sig fig rules for multiplication and division

rounded to the number of digits that corresponds to the least number of significant figures

Sig fig rules with addition or subtraction

rounded to the measurement with the fewest decimal places

The Electron cathode

streams of negatively charged particles were found to emanate from cathode tubes, causing fluorescence

The electron beam

Thomson measured the charge/mass ratio of the electron to be 1.76 108 coulombs/gram

Millikan oil-drop experiment

Once the charge/mass ratio of the electron was known, determination of either the charge or the mass of an electron would yield the other

Radioactivity

the spontaneous emission of radiation by an atom

three types of radiation

alpha rays, beta rays, and gamma rays

How are elements symbolized?

By one or two letters

All atoms of the same element have the same number of protons, which is called …

the atomic number

Isotopes

atoms of the same element with different masses

Average mass is calculated…

from the isotopes of an element weighted by their relative abundances

Nonmetals are on the ______ side

right

Metalloids border the _________

stair step line

Metals are on the _____ side

left

Molecular compounds

are composed of molecules and almost always contain only nonmetals

Diatomic molecules

Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine

Empirical formulas

give the lowest whole-number ratio of atoms of each element in a compound

Molecular formulas

give the exact number of atoms of each element in a compound

Structural formulas

show the order in which atoms are bonded

Perspective drawings

show the three-dimensional array of atoms in a compound

Cations

positive and are formed by elements on the left side of the periodic chart

Anions

negative and are formed by elements on the right side of the periodic chart

Ionic compounds

are generally formed between metals and nonmetals

If the anion is an element, change ______

it’s ending to -ide

When there are two oxyanions involving the same element: the one with fewer oxygens ends in

\-ite

When there are two oxyanions involving the same element: the one with more oxygens ends in

\-ate

Charges increase as you go from

right to left

The one with the second fewest oxygens ends in…

\-ite

The one with the second most oxygens ends in…

\-ate

The one with the fewest oxygens has the prefix ___ __and ends in__ _____

hypo-; -ite

The one with the most oxygens has the prefix ___ __and ends in__ ___

per-; -ate

If the anion in the acid ends in -ide, change the ending to __ __acid and add the prefix__ ____

\-ic; hydro-

If the anion in the acid ends in -ite, change the ending to ____ acid

\-ous

If the anion in the acid ends in -ate, change the ending to ____ acid

\-ic

The ending on the more electronegative element is changed to ____

\-ide

Chemical reactions are

conversion of a substance to one or more substances with new chemical and physical properties

Chemical reactions involve…

regrouping of atoms

During chemical reactions, energy can also be __*or*__ _____

absorbed or released

Subscripts tell the number of _____

atoms of each element in a moleculeCoe

Coefficient tell the number of _______

molecules

Combination reactions

two or more substances react to form one product

Decomposition reactions

one substance breaks down into two or more substances

Combustion reactions

Rapid reactions that produce a flame (most often involve hydrocarbons reacting with oxygen in the air)

Molecular mass

The sum of the average atomic masses of the elements in the substance

Molar mass

The mass in grams of one mole of a substanceA

Formula mass

Sum of all the molar masses of the atoms that make up the simplest electrically neutral group of ions in the ionic compound

Percent composition

gives the mass percent of each element in a compound

Empirical formulas express …

the relative number of atoms in the smallest whole numbers possible

If the % composition of each element is known for compound,

its empirical formula can be determined

Combustion analysis

a compound of unknown composition is burned in the presence of oxygen

Combustion products

The relative number of atoms is determined by calculating the number of moles produced

In order to assign molecular formula, the ____ ___ must be experimentally determined

molar mass