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Molecules, Compounds & Chemical Reactions

molecule animation

I).  Molecules and Compounds

A).  Compound:   

B).  Molecule

C).  Molecular Formula

The number of atoms of the element in the molecule is written in smaller print on the right side of the atomic symbol.

A large number on the left indicates how many molecules are present.

II). Mixtures

Two or more components physically intermixed together.

A).  Solutions

Solutions consist of a solvent or dissolving medium and a solute or dissolved substance. 

  (i.e.  solvent = water;  solute = NaCl)

B).  Colloids


C).  Suspensions





properties of atoms





separate substances

cannot be easily separated

can be separated by physical means


or heterogeneous

does not apply

can be either homogenous or heterogeneous

III). Chemical Bonds

Electrons can be

 1. ‘taken’ ionic bond

2.  ‘shared equally’ nonpolar covalent

3.  ‘shared unequally’ polar covalent

    A). Ionic Bonds

An electron transfer between atoms

Ionic bonds only occur when the atom needs to gain or lose 1 or 2 electrons

    B). Covalent Bonds

Charged ions share electrons

Non Polar Molecule Polar Molecule
non polar molecule polar molecule

In nonpolar molecules shared equally.

In polar molecules  not shared equally

chemical bonds

    C). Hydrogen Bonds

Form when hydrogen is already covalently bonded to one electronegative atom


IV). Chemical Reactions

        A). chemical equations

reactants > products

Reactants:  beginning material on the left

Products:  ending material on the right


Chemical equations must be balanced

Matter cannot be created or destroyed


B). Energy Flow

Chemical reactions result in the net absorption or release of energy

C). Factors influencing chemical reactions

1).  Particle size

2).  Temperature

3).  Concentration


Catalysts lower the amount of energy need for the reaction to occur thus speeding up the reaction without being used up themselves.

 V).  Inorganic Compounds

  Compounds that do not contain carbon bonded to hydrogen

A). Water

1). High heat capacity

2). High heat of vaporization

3). Polarity/solvent properties

4). Reactivity

5). Cushioning

B). Salts

A salt is an ionic compound consisting of ions other than H+ or OH-

i.e. Na+, K+, P+ Ca++, etc

Breaks up in water because the polarity of water pulls apart ionically bonded molecules and they conduct an electrical current in solution

C). Acids & Bases

Acids & Bases are covalently bonded molecules that dissociate in water

1). Acids

  An acid is a substance that releases hydrogen ions (H+).  When acids dissociate they release an H+ (protons)

HCl H+  +  Cl-


2). Bases

Bases are proton acceptor and usually contain a hydroxyl ion (OH-).

When bases dissociate they release an OH- (ion)

NaOH  <-> Na+ + OH-

  Basic = Alkaline

3). pH

The concentration of H+ in solution is measured in pH units.


The pH scale runs from 0 to14 and is logarithmic which, means there is a tenfold change in between each pH unit.


pH 7 the H+ = OH-.

pH lower than 7 is acidic and the H+ > OH-.

pH greater than 7 is basic or alkaline and the OH- > H +.

hydrogen ion concentration and pH