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Molecules, Compounds & Chemical Reactions
I). Molecules and Compounds
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.
Two or more components physically intermixed together.
Solutions consist of a solvent or dissolving medium and a solute or dissolved substance.(i.e. solvent = water; solute = NaCl)
properties of atoms
cannot be easily separated
can be separated by physical means
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|
In nonpolar molecules shared equally.
In polar molecules not shared equally
C). Hydrogen Bonds
Form when hydrogen is already covalently bonded to one electronegative atom
IV). Chemical Reactions
A). chemical equations
reactants > products
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
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
1). High heat capacity
2). High heat of vaporization
3). Polarity/solvent properties
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
An acid is a substance that releases hydrogen ions (H+). When acids dissociate they release an H+ (protons)
HCl → H+ + Cl-
Bases are proton acceptor and usually contain a hydroxyl ion (OH-).
When bases dissociate they release an OH- (ion)
NaOH <-> Na+ + OH-
Basic = Alkaline
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 +.