AP Chemistry: Unit 4 Summary
4.1 Introduction for Reactions
Physical Changes
When a substance undergoes a physical process, the composition does not
change
Physical properties (shape, solubility at different temperatures) may change
These types of changes DONT RESULT IN A CHANGE IN COMPOSITION of the
substance
Separation of mixtures is an example of a substance undergoing physical
change
Phase changes are an example of physical process
Chemical Changes
When a substance undergoes a reaction a new substance is formed
Chemical Properties change in this type of reaction, such as reactivity with
acids or flammability, resulting in a new composition
Heat and light being produced shows proof of a chemical change
Formation of a precipitate or formation of a new substance show chemical
change evidence
Chemical changes take precedent over physical changes
4.2 Net Ionic Equations
Balanced Equations
Can be used to represent physical processes
Can also be used to represent chemical changes
AP Chemistry: Unit 4 Summary 1
, H2 O (s)
→ H2 O (l)
Chemical changes are a result of the rearrangement of atoms into new
combinations
Balanced equations demonstrate that mass is conserved in chemical reactions
Main types of reactions
Single Replacement
Double Replacement
Combustion
Synthesis
Decomposition
Reagents and products are NOT the same chemical composition
2H2 (g) + O2 (g)
→ 2H2 O(l)
Equation Types (Including Net Ionic)
Balanced Molecular Equations: show all species included in a reaction.
Equations indicated mass conservation.
Complete Ionic Equations: shows ions in aqueous solution as they separate
charged particles. Equations can be used to identify spectator ions.
Net Ionic Equations: doesn’t include spectator ions. It is only useful to
represent substances undergoing a chemical change.
Solubility Rules
Soluble:
All salts of Group A1
Ammonium
All salts of nitrates, chlorates, and acetates
All salts of halides EXCEPT silver(I), copper(I), lead(II), and mercury(II)
AP Chemistry: Unit 4 Summary 2
4.1 Introduction for Reactions
Physical Changes
When a substance undergoes a physical process, the composition does not
change
Physical properties (shape, solubility at different temperatures) may change
These types of changes DONT RESULT IN A CHANGE IN COMPOSITION of the
substance
Separation of mixtures is an example of a substance undergoing physical
change
Phase changes are an example of physical process
Chemical Changes
When a substance undergoes a reaction a new substance is formed
Chemical Properties change in this type of reaction, such as reactivity with
acids or flammability, resulting in a new composition
Heat and light being produced shows proof of a chemical change
Formation of a precipitate or formation of a new substance show chemical
change evidence
Chemical changes take precedent over physical changes
4.2 Net Ionic Equations
Balanced Equations
Can be used to represent physical processes
Can also be used to represent chemical changes
AP Chemistry: Unit 4 Summary 1
, H2 O (s)
→ H2 O (l)
Chemical changes are a result of the rearrangement of atoms into new
combinations
Balanced equations demonstrate that mass is conserved in chemical reactions
Main types of reactions
Single Replacement
Double Replacement
Combustion
Synthesis
Decomposition
Reagents and products are NOT the same chemical composition
2H2 (g) + O2 (g)
→ 2H2 O(l)
Equation Types (Including Net Ionic)
Balanced Molecular Equations: show all species included in a reaction.
Equations indicated mass conservation.
Complete Ionic Equations: shows ions in aqueous solution as they separate
charged particles. Equations can be used to identify spectator ions.
Net Ionic Equations: doesn’t include spectator ions. It is only useful to
represent substances undergoing a chemical change.
Solubility Rules
Soluble:
All salts of Group A1
Ammonium
All salts of nitrates, chlorates, and acetates
All salts of halides EXCEPT silver(I), copper(I), lead(II), and mercury(II)
AP Chemistry: Unit 4 Summary 2
