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The Scientific Method

Chemistry is the science that deals with the materials of the universe and the changes that these materials undergo.
Steps:
1. State the problem and collect data (make observ­ations)
2. Formulate hypotheses. A hypothesis is a possible explin­ation for the observ­ation.
3. Preform Experi­ments. Gather new inform­ation that allows us to decide whether the hypothesis is supported by the new inform­ation we have learned

Measur­ements and Calcul­ations

Scientific notation expresses a number as a product of a number between 1 and 10 and the approp­riate power of 10.
Ex. (100= 1.0×102 , 0.010=­1.0×10-2)
If the decimal is moved to the left, the power of 10 is positive ; if the decimal is moved to the right, the power of 10 is negative.

Unit Prefixes

Signif­icant Figures

The numbers recorded in a measur­ement are called signif­icant figures.
1. Nonzero integers always count as signif­icant figures. Ex. (4567 has four nonzero integers that count as signif­icant figures.)
2. Zeros.
a. leading zeros never count as signif­icant figures. Leading zeros are all zeros that precede nonzero integers.
b. captive zeros always count as signif­icant figures. Captive zeros are zeros that fall in between two nonzero digits.
c. trailing zeros are sometimes signif­icant figures. Trailing zeros are zeros right at the end of a number. They are only signif­icant if the number is written with a decimal. (Ex. The number 100 only has one SF 1 ; but the number 100. has three SF.
3. Exact Numbers never limit the number of signif­icant figures in a calcul­ation.
Signif­icant figures also apply to scientific notation.

Temper­ature Conversion

TC Equations

Temper­ature in Kelvins = Temper­ature in Celsius + 273
Temper­ature in Celsius = Temper­ature in Kelvin - 273
Temper­ature in Fahrenheit = 1.80( Temper­ature in Celsius) +32
Temper­ature in Celsius = Temper­ature in Fahrenheit - 32 / 1.80

Density, Mass, and Volume

Elements and Compounds

An element is a substance that cannot be broken down into other substances by chemical means.
When elements combine, they form compounds, which are substances that can be broken down into elements by chemical means.

Pure Substances and Mixtures

A pure substance is either an element or compound.
A mixture can be defines as something that has variable compos­ition.
Mixtures can be classified as either homoge­neous or hetero­gen­eous.
A homoge­neous mixture is the same throug­hout. This type of mixture is also called a solution.
A hetero­geneous mixture contains regions that have different properties from those of other regions.
These mixtures can be separated through distil­lation and filtration.
 

Mixtures

Dalton's Atomic Theory

1. Elements are made of tiny particles called atoms.
2. All atoms of a given element are identical.
3. The atoms of a given element are different from those of any other element.
3. Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and types of atoms.
4. Atoms are indivi­sible in the chemical process. Atoms are not created nor destroyed in chemical reactions. A chemical reaction simply changes the way the atoms are grouped together.

Atom Structure

Isotopes

Periodic Table

Ions

An ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
A cation is a positively charged ion; an ion that has lost electrons.
An anion is a negatively charged; an atom that has gained electrons.
Alkali Metals are the most reactive metals that can form cations easily by only needing to lose one valence electron.
Halogens are the most reactive nonmetals that can form anions easily by only needing to gain one valence electron.
Noble Gasses have 8 valence electrons so they are already stable.
An ionic bond is a chemical bond resulting from the attraction between oppositely charged ions.
A chemical compound must have a net charge of 0 (zero)

Ionic charges

  

Common Simple Cations and Anions

Cation
Name
Anion
Name
H+
hydrogen
H-
hydride
Li+
lithium
F-
fluoride
Na+
sodium
Cl-
chloride
K+
potassium
Br-
bromide
Cs+
cesium
I-
iodide
Be2+
beryllium
O2-
oxide
Mg2+
magnesium
S2-
sulfide
Ca2+
calcium
Ba2+
barium
Al3+
aluminum
Ag+
silver
Zn2+
zinc

Common Type II Cations

Ion
Systematic Name
Older Name
Fe3+
iron(III)
ferric
Fe2+
iron(II)
ferrous
Cu2+
copper(II)
cupric
Cu+
copper(I)
cuprous
Co3+
cobalt­(III)
cobaltic
Co2+
cobalt(II)
cobaltous
Sn4+
tin(IV)
stannic
Sn2+
tin(II)
stannous
Pb4+
lead(IV)
plumbic
Pb2+
lead(II)
plumbous
Hg2+
mercur­y(II)
mercuric
Hg22+
mercury(I)
mercurous
Mercury(I) ions always occur bound together in pairs to form Hg22+.

Nomenc­lature

Common Polyatomic Ions.

Rules for Naming Acids

If the anion does not contain oxygen, the acid is named with the prefix hydro- and the suffix -ic attatched to the rootname of the element.
Ex. HCl= hydro-chlor-ic acid
2. When anions contain oxygen, the acid name is formed from the root name of the central element of the anion or the anion name with the suffix of -ic or -ous.
When the anion name ends in -ite, the suffix -ic is used.
(Ex. H2SO4 = SO42-(sulfate) = Sulfric Acid)
When the anion name ends in -ite, the suffix -ous is used in the acid name.
(Ex. H2SO3 = SO32- (sulfite) = Sulfurous acid)

Chemical Equations

We represent a chemical reaction by writing a chemical equation in which the chemical reactions (the reactants) are shown to the left of an arrow and the chemicals are formed by the reaction (the products) are shown to the right of the arrow.
In the process of balancing equations is that atoms are conserved in a chemical reaction.
The identities (formulas) of the compounds must never be changed in balancing a chemical equation.

Balancing Equations

Step 1 Read the descri­­ption of the chemical reaction.
Step 2 Write the unbalanced equation that summarizes the inform­ation from step 1.
Step 3 Balancing the equation by inspec­tion, starting with the most compli­cated molecule. Proceed element by element to determine what coeffi­cients are necessary so that the same number of each type of atom appears on both the reactant and the product side.
Step 4 Check to that the coeffi­cients used, give the same number of each type of atom on both sides of the arrow. Also check to see that the coeffi­cients used are the smallest integers that give the balanced equations. This can be cone by determ­ining whether all coeffi­cients can be divided by the same integer to give a set of smaller integer coeffi­cients.
 

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  • Published: 24th September, 2018
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