J

Physical Science

Outline of Chemical Reactions

1. Law of Conservation of Mass

  • Total mass of reactants = total mass of products.

2. Chemical Equations

  • Description of reactions using element symbols and chemical formulas.

  • Reactants: Starting substances (left of the arrow).

  • Products: Substances produced (right of the arrow).

  • Separation of reactants/products by plus signs.

3. Bond Formation and Breaking

  • Atoms rearrange when chemical bonds break.

  • Energy required for particles to collide and break bonds.

  • No new atoms created; existing atoms rearrange.

4. Changes in Matter

A. Physical Changes

  • Do not produce new substances; properties may change.

B. Chemical Changes

  • Produce new substances; different properties than reactants.

  • Examples: Change in color, odor, bubble formation, precipitate.

  • Energy changes: Warming, cooling, light release.

5. Types of Chemical Reactions

A. Synthesis Reaction

  • Two or more substances combine: A + B → C.

B. Decomposition Reaction

  • One compound breaks down: AB → A + B.

C. Replacement Reaction

  • Single Replacement: One element replaces another in a compound.

  • Double Replacement: Negative ions switch places in two compounds.

D. Combustion Reaction

  • Substance combines with oxygen, releasing energy (thermal and light).

6. Reaction Rate Factors

A. Surface Area

  • Increased surface area increases collision rate.

B. Temperature

  • Higher temperatures increase particle speed, leading to more collisions.

C. Concentration and Pressure

  • Higher concentration increases collision rates; increased pressure in gases brings particles closer together.

7. Energy Changes in Reactions

A. Activation Energy

  • Minimum energy required to initiate a reaction.

B. Exothermic Reactions

  • Release thermal energy; more energy released when a bond is broken in the products.

C. Endothermic Reactions

  • Absorb thermal energy; require constant energy input to continue. More energy is required to break bonds in the reactants

Key terms: endothermic and exothermic

  • exothermic need to release more energy to form a bond in the products than to break a bond in the reactants

  • endothermic need more energy to to break the bonds in the reactants than to create bonds in the products