Chemical Reactions: Basics
This term describes the starting substances in a chemical reaction.
reactants
Copper turning green is an example of this type of evidence.
color change
This scientific law states that matter is neither created nor destroyed in chemical reactions.
Law of Conservation of Mass
The first step in writing a balanced equation is writing this initial form.
skeleton (unbalanced) equation
A + B → AB represents this type of reaction.
synthesis (combination) reaction
Chemical reactions involve breaking these and forming new ones.
chemical bonds
Bubbling from an acid–metal reaction shows the formation of this.
gas
According to the law, the mass of the reactants must equal this.
mass of the products
These whole numbers placed in front of formulas are used to balance atoms.
coefficients
AB → A + B represents this type of reaction.
decomposition reaction
In a chemical reaction, atoms are neither created nor destroyed but do this.
rearrange
The appearance of a solid in a liquid mixture is this type of evidence.
precipitate formation
In molecular terms, the number and type of these must be the same in reactants and products.
atoms
In balancing C₂H₆ + O₂ → CO₂ + H₂O, this element should be balanced first.
hydrogen
In the reaction NaCl + AgNO₃ → NaNO₃ + AgCl, this type of reaction occurs.
double replacement reaction
These are the new substances formed in a chemical reaction.
products
A reaction that absorbs or releases heat shows this type of evidence.
emperature change
If 4.0 g of hydrogen react with 32.0 g of oxygen, the total mass of water produced must be this.
36.0 g
Changing these would change the compound’s identity, so they must never be altered when balancing.
subscripts
A reaction with oxygen as a reactant and CO₂ + H₂O as products is this type.
combustion reaction
A reaction where methane forms from hydrogen and carbon is an example of this broad type of process, since atoms combine into a new molecule.
synthesis/combination reaction
Fireworks demonstrate this form of reaction evidence.
light emission
When balancing equations, you must change this part of the formula but never the subscripts.
coefficients
The balanced equation for C₂H₆ combustion includes this coefficient in front of O₂.
7
Balanced: 2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O
The reaction 4 Fe + 3 O₂ → 2 Fe₂O₃ is best classified as this reaction type.
combination/synthesis reaction