Solution = homogeneous mixture on the molecular, atomic and/or ionic level.

solute + solvent = solution

Examples of solutions where (s) = solid, (l) = liquid, (g) = gas:
salt(s) + water(l)
nitrogen(g) + oxygen(g)
oxygen(g) + water(l)
alcohol(l) + water(l)
mercury(l) + copper(s)
platinum (s)+ gold(s)
 

Terms used to describe solutions

unsaturated, saturated
dilute, concentrated
miscible, immiscible,
aqueous solution,
"like dissolves like",
colloidal dispersion

Concentration Units
 

% by mass = mass solute   x 100
                     mass solution     1
 

ppm by mass = mass solute    x 10⁶
                        mass solution     1
 

Molarity = M = moles of solute
                         liters of solution

Example problems:
Calculate the % by weight and M (molarity) of NaCl in a solution made by dissolving 18g NaCl in 99g H₂O to produce a solution of density 1.13 g/cm3.

% = 18 g  salt                     x 100 =
       (99g water + 18 g salt)       1
 

                       18g NaCl x 1 mol
                                 1         58.5g
M =     ____________________________=

                  117 g soln x 1 mL x 1L
                        1            1.13 g 10³ mL
 

An automobile battery contains 4.5 M H2SO4 with a density of 1.26 g/mL
What is the % by mass of H2SO4 in this solution?