Chemical Reactions

What is a chemical reaction?

A process where substances transform into new substances by making or breaking chemical bonds.

What changes occur in chemical reactions?

Atoms rearrange, forming substances with different properties from the original reactants.

What are evidence of chemical reactions?

Observable changes like color, energy (heat/light/sound), phase, or smell changes.

What does (s) mean in reaction notation?

Solid.

What does (l) mean in reaction notation?

Liquid.

What does (g) mean in reaction notation?

Gas.

What does (aq) mean in reaction notation?

Aqueous, dissolved in water.

How do you write the general reaction format?

Reactants -> Products; arrow shows the transition/process.

What are diatomic elements?

Elements so reactive they exist naturally only as diatomic molecules (2 atoms bonded) or bonded with others.

Which elements exist naturally as diatomic molecules?

Hydrogen (H2), Nitrogen (N2), Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), Iodine (I2)

How many diatomic elements form the "7" shape on the periodic table?

Six of the seven.

What is the Law of Conservation of Mass?

Matter cannot be created or destroyed; atom counts must be equal on both sides of a reaction.

How do you balance water formation?

Adjust H and O atoms so both sides match; e.g., 2 H2 + O2 -> 2 H2O.

What is a decomposition reaction?

One compound breaks down into simpler substances.

General form of decomposition reactions?

AB -> A + B

What is a synthesis reaction?

Two or more substances combine to form a single compound.

General form of synthesis reactions?

A + B -> AB

What is a single replacement reaction?

One element replaces another in a compound.

General form of single replacement reactions?

A + BC -> AC + B

What is a double replacement reaction?

Two ionic compounds exchange ions to form new compounds.

General form of double replacement reactions?

AB + CD -> AD + CB

What is a combustion reaction?

A substance burns in oxygen, producing energy, CO2, and H2O.

General form of combustion reactions?

Organic + O2 -> CO2 + H2O

What is the main product of a synthesis reaction?

One single compound.

What always occurs in a combustion reaction?

O2 reacts with a substance, producing CO2 and H2O.

What happens in decomposition reactions?

One compound splits into two or more simpler substances.

How to recognize a single replacement reaction?

One element and one ionic compound are involved; one element swaps.

How to recognize a double replacement reaction?

Two ionic compounds are present; ions swap to form new compounds.

How can you spot a chemical reaction?

Look for color, energy, or phase changes.

Why are diatomic elements never found alone naturally?

They’re too reactive; they exist as diatomic molecules or bonded with other elements.

What does the arrow in a chemical equation indicate?

The transition from reactants to products.

Give an example of hydrogen as a diatomic element.

Hydrogen exists as H2, not as single H atoms.

What observable energy changes indicate a reaction?

Heat, bright light, or sound production.

What phase changes indicate a chemical reaction?

Gas production (smell/fizz) or solid formation.

What are state symbols used for?

Indicating the phase of substances in chemical equations.

What is the purpose of reaction notation?

To represent reactants, products, and their states in a standardized way.

What is the significance of balancing reactions?

To obey the Law of Conservation of Mass.

Give a general example of a synthesis reaction.

2 H2 + O2 -> 2 H2O

Give a general example of a decomposition reaction.

2 H2O2 -> 2 H2O + O2

Give a general example of a single replacement reaction.

Zn + CuSO4 -> ZnSO4 + Cu

Give a general example of a double replacement reaction.

AgNO3 + NaCl -> AgCl + NaNO3

Give a general example of a combustion reaction.

CH4 + 2 O2 -> CO2 + 2 H2O