Scientific method- a logical approach to solving problems by observing and collecting
data, formulating hypotheses, testing hypotheses, and formulating theories that are
supported by data.
Observing and Collecting Data
System- a specific portion of matter in a given region or space that has been selected for
study during an experiment or observation
Formulating Hypotheses
Hypothesis- a testable statement in “if- then” format.
Testing Hypotheses
Experiment- a set of procedures used to test a hypothesis
Controls- the experimental conditions that remain constant
Dependent Variable- any condition that changes (y-axis) scientist has no control over
this variable.
Independent Variable- determines the dependent variable (x-axis) scientist has control
over this variable.
Model- in science is more than a physical object, it is often an explanation of how
phenomena occur and how data or events are related
Theory- is a brand generalization that explains a body of facts or phenomena
Law- how things happen in nature, descriptions of specific relationships under certain
conditions in nature. Offer no explanations.
Theory- why things happen in nature, well supported descriptions.
*laws do not become theories, theories do not become laws.
Quantity- something that has magnitude, size, or amount
Scientists all over the world have agreed on a single measurement system: SI
Weight- a measure of the gravitational pull on matter.
Derived Unit- combination of SI base units
Mass- a measure of the amount of matter.
Matter- anything that has mass and volume.
Volume- the amount of space occupied by an object
Density- the ratio of mass to volume, or mass divided by volume
States of matter- liquid, solid, gas, plasma
1). Liquid- definite volume and indefinite shape.
2). Solid- Definite volume and shape.
3). Gas- No definite volume or shape.
4). Plasma- high temperature physical state of matter in which atoms lose most of their
electrons.
Conversion factor- a ratio derived from the equality between two different units that can
be used to convert from one unit to the other- equal to one.
Dimensional analysis- a mathematical technique that allows you to use units to solve
problems involving measurements.
Accuracy- refers to the closeness of measurements to the correct or accepted value of the
quantity measured
Precision- refers to the closeness of a set of measurements of the same quantity made in
the same way (reproducibility of results)
Percent error-
Error in measurement- some error or uncertainty always exists in any measurements
Significant figures- in a measurement consist of all the digits known within certainty
plus one final digit, which is somewhat uncertain or is estimated
*All non- zero numbers are significant
* A zero between significant figures is significant
* A zero to the right of the decimal and at the end is significant
* Zero in ones digit, with decimal point shown, nothing after decimal, is significant.
Rule for multiplication and Division:
-The answer can have no more significant figures than the measurement
with the fewest significant figures.
Rule for Addition and Subtraction:
-The answer can have no more decimal places than the measurement
with the fewest decimal places.
*if both are whole numbers round to the left-most uncertain digit (LAST SIG FIG)
Scientific Notation- numbers are written in the form Mx10n, where the factor M is a
number between 1 and 9.99999999999999 and n is a whole number.
Problem solving Strategy
1) analyze 2) Plan 3) Solve 4) evaluation
Directly proportional- two quantities directly proportional to each other. If dividing one
by the other gives a constant value.
Inversely proportional- two quantities are inversely proportional if their product is
constant.
Classification of Matter
Mixture- physical blend of two or more kinds of matter, each of which retains its own
identity and properties.
Homogenous mixture- uniform in composition, aka solutions.
Heterogeneous mixture- not uniform in composition.
Ways to separate mixtures
1). Filtration
2). Paper chromatography (separate pigments)
3). Centrifuge
4). Crystallization
5). Distillation (separation based on boiling points)
Pure substances
Pure substance- has a fixed composition
* The physical and chemical properties are the same in all samples and it has the same
composition in all samples.
*Pure substances are either compounds or elements.
* The chemical and physical properties of compounds are quite different than their
component elements.
Basic building blocks of matter
Atom- smallest unit of an element that maintains the chemical identity of that element.
Element- a pure substance that cannot be broken down into simpler, stable substances
and is made of one type of atom.
Compound- a substance that can be broken down into simpler stable substances. Each
compound is formed from the atoms of 2 or more elements that are chemically bonded in
fixed proportions. You can write a formula for a compound, 2 or more capital letters.
*compounds have different properties than the elements they are made of.
Law of Conservation of Mass- states that mass is neither created nor
destroyed during ordinary chemical reactions or physical change.
Mass before = mass after
Law of Definite Proportions- the fact that a chemical compound contains the
same elements in exactly the same proportions by mass regardless of the size of
the sample or source of the compound.
*Water is H2O, if not H2O, it is not water. Water is the same composition
everywhere.
Law of Multiple Proportions- if two or more different compounds are composed
of the same two elements, then the ratio of the masses of the second element
combined with a certain mass of the first element is always a ratio of small whole
numbers.
Dalton’s Atomic Theory
* All matter is composed of extremely small particles called atoms
* Atoms of a given element are identical in size, mass, and other properties.
Atoms of different elements differ in size, mass, and other properties
* Atoms cannot be subdivided, created, or destroyed
* Atoms of different elements combine in simple whole number ratios to form
chemical compounds
*In chemical reactions, atoms are combined, separated, or rearranged.
Modern atomic theory called the Quantum Mechanical Model or
Electron Cloud Model.
*Three major differences from Dalton’s theory
-1- Modern theory- atoms are not indivisible,
we have protons, neutrons, and electrons.
-2-Atoms can be changed from one element to another,
not by chemical reactions, but by nuclear reactions.
-3-Atoms of the same element are not all exactly alike (isotopes)
Cathode- ray tubes supplied evidence of the existence of electrons, which are
negatively charged sub-atomic particles that have relatively little mass
Thomson- electron, cathode ray tube, plum pudding model of the atom,
Rutherford- gold foil experiment, proton and nucleus, used alpha particles.
OBSERVATION
MOST ALPHAS PARTICLES WENT
STRAIGHT THROUGH
1/8000 DEFLECTED
CONCLUSION
MOST OF ATOM EMPTY SPACE
ELECTRONS HERE
ATOMS HAVE DENSE POSITIVE
CENTER
Millikan- oil drop experiment, charge of electron
Introduction to Periodic Table
Groups- vertical columns of the periodic table (family)
*Each element has a unique symbol.
* The periodic table shows the elements organized by their chemical properties.
4 Family Names:
Group 1A: Alkali Metals
Group 2A: Alkaline Earth Metals
Group 7A: Halogens
Group 8A: Noble Gases
Periods- the horizontal rows of elements in the periodic table
* Each group contains elements with similar chemical properties (due to the number of
valence electrons)
* Properties vary throughout periods.
Types of Elements
* The elements can be classified as metals, nonmetals, metalloids, and noble gases.
* These classes occupy different areas of the periodic table
Metal- an element that is a good electrical and heat conductor
Malleability- can be hammered or rolled into thin sheets
Ductile- can be drawn into fine wire
Tensile strength- the ability to resist
Nonmetal- an element that is a poor conductor of heat and electricity
Metalloid- an element that has some characteristics of the metals and some
characteristics of nonmetals
Noble Gases- don’t chemically react with any other elements. They are unreactive and
are found in Group 18.
The following should be put on flash cards also:
ionic compounds (flash card)
*made of metal and nonmetal (or polyatomic ions)
*ionic bonding
*formula units for representative particles
molecular compounds (flash card)
* nonmetals only
*covalent bonding
*molecules for representative particles
naming ionic compounds (flash card)
1. name first element
2. name second element, change ending to -ide
*never change ending of polyatomic ion
*cation (which is the metal, unless it is ammonium) with more than one possible
charge must have roman numeral.
(Roman numeral equals the charge of the cation)
naming molecular compounds (flash card)
1. name first element
2. name second element, change ending to -ide
*must use prefixes for subscripts.
Exceptions for prefixes--> 1. no mono for first element
1. a 2 syllable prefix, added to a vowel, drop vowel on prefix
CO = carbon monoxide (illustrates both rules)
writing molecular formulas (flash card)
*prefixes give you the subscripts
writing formula units (flash card)
*overall positive and overall negative charges must cancel out, be neutral, which
means numerically it is zero for the final charge. (use George)
*if you add a subscript to polyatomic ion you must use ( ). Or stated another
way if you have more than one of a polyatomic ion you must add ( ).
How do you know when you have a polyatomic ion? (flash card)
1. you see ( )
2. -ate or -ite (exceptions ammonium, cyanide, and hydroxide)
3. ionic with 3 or more capital letters.
When does a cation need a Roman numeral? (flash card)
*when it has more than one possible charge, which means it is not in IA, IIA, IIIA
or one of the 3 exceptions ---> silver, cadmium, and zinc.
Naming acids (flash card)
*anion ends in –ide = add hydro- change ending to –ic and acid
*anion ends in –ate = change ending to –ic and acid
*anion ends in –ite = change ending to –ous and acid
Writing formula for acid (flash card)
 work backwards with rules to get anion
 cation is always H+
 make compound neutral. (use George)