Chapter 8 - Chemical Reactions

Evidence of Chemical Change

Indications that a chemical reaction has occurred, including color change, gas evolution, formation of precipitate, and energy change.

Energy in Reactions

All reactions have energy changes; forms include heat, light, kinetic energy (KE), and potential energy (PE).

Kinetic Energy (KE) formula

$KE = \frac{1}{2}mv^2$.

Law of Conservation of Energy

Energy is neither created nor destroyed; it is conserved.

Endothermic Reaction

A reaction that absorbs energy, expressed as Reactants + Energy → Products.

Exothermic Reaction

A reaction that releases energy, expressed as Reactants → Products + Energy.

Law of Conservation of Matter

Matter is neither created nor destroyed, only conserved.

Balancing Reactions

Using coefficients to ensure the number of atoms of each element is equal on both sides of a reaction.

(s), (l), (g), (aq)

Phase designations: (s) is solid, (l) is liquid, (g) is gas, (aq) is aqueous (dissolved in water).

Synthesis Reaction

A reaction where two or more reactants combine to form a single product, e.g., A + B → AB.

Decomposition Reaction

A reaction where a compound breaks down into simpler substances, e.g., AB → A + B.

Combustion Reaction

A reaction that involves oxygen (O₂), usually producing CO₂ and H₂O as products.

Single Replacement Reaction

A reaction where an element replaces another element in a compound, e.g., A + BC → AC + B.

Double Replacement Reaction

A reaction where two ionic compounds exchange partners, e.g., AB + XY → AY + XB.

Acid-Base Reaction

A reaction involving an acid and a base, producing water and a salt, e.g., HA + BOH → H₂O + BA.

Dissolving vs Dissociation

Dissolving involves a physical change as compounds mix, while dissociation involves ionic compounds separating into ions in water.

Ionic Compounds in Water

Ionic compounds dissociate into their respective ions when dissolved in water, e.g., NaCl(s) → Na⁺(aq) + Cl⁻(aq).

Molecular Compounds in Water

Molecular compounds dissolve without dissociating into ions, e.g., C₆H₁₂O₆(s) → C₆H₁₂O₆(aq).