Chemistry Chapter: Reaction Rates & Bonding

Factors Affecting Reaction Rate

• Higher concentration of reactants increases the rate of reaction due to more collisions.
• Agitation, such as mixing or stirring, increases collisions and keeps reactants in contact.
• Higher temperature increases reaction rate as heat provides more kinetic energy for particles to move faster.
• Dividing reactants into smaller pieces increases surface area, allowing for faster reactions from outer layers.

Atomic Bonding

• Atoms form compounds to gain stability by achieving a full outer shell of electrons.
• Chemical bonding occurs through covalent, ionic, and metallic bonds.

Covalent Bonds

• Covalent bonds involve sharing valence electrons between two or more non-metals.
• Shared electrons orbit all nuclei forming a covalent compound or molecule.

Ionic Bonding

• Ionic bonds involve a non-metal and metal atom forming a bond through losing or gaining electrons to achieve a full outer shell.
• The swap-drop method can be used to determine the chemical formula of ionic compounds by using the ionic charges from the periodic table.
• Ions are charged atoms formed by losing or gaining electrons.
• Cations are positively charged ions while anions are negatively charged.

Polyatomic Ions

• Polyatomic ions are two or more atoms bonded covalently, acting as a single charged unit.
• Polyatomic ions have specific charges based on their covalent bonding.
• Examples of polyatomic ions include:
  • Ammonium (NH₄⁺¹)
  • Hydroxide (OH⁻¹)
  • Nitrate (NO₃⁻¹)
  • Sulfate (SO₄⁻²)
  • Sulfite (SO₃⁻²)
  • Nitrite (NO₂⁻¹)
  • Phosphate (PO₄⁻³)
  • Hydrogen sulfate (HSO₄⁻²)
  • Carbonate (CO₃⁻²)
• Strong electrostatic attraction exists between cations and anions due to their opposite charges.

Metallic Bonds

• Metallic bonding occurs between atoms of the same element, forming metals.
• Atoms lose electrons, creating a "free sea" of electrons surrounding positive metal ions.
• The free electrons create a lattice structure, making metals good conductors of heat and electricity.
• Metallic bonds are weaker than ionic bonds.

Naming Compounds

Covalent Compound Naming

• Covalent compounds are named with prefixes to indicate the number of each atom present.
• The second element ends in "-ide".

Ionic Compound Naming

• Ionic compounds are named with the metal first followed by the non-metal ending in "-ide".
• The swap-drop method helps determine the chemical formula of ionic compounds.
• If an ion has multiple charges, roman numerals are used to distinguish them.

Combustion Reactions

• Combustion reactions are oxidation reactions involving the transformation of chemical energy into heat energy.
• Hydrocarbons, containing carbon and hydrogen, burn in the presence of oxygen to produce CO₂ and H₂O in complete combustion.
• Incomplete combustion occurs when there isn't enough oxygen, producing harmful products like carbon monoxide (CO) and carbon soot.

Corrosion Reactions

• Corrosion is an oxidation reaction where metals react with oxygen, forming compounds on their surfaces.
• Metals corrode at different rates depending on their properties.

Iron Corrosion (Rust)

• Iron oxide (Fe₂O₃) is the scientific name for rust.
• Rust causes significant damage as it lacks a protective barrier.

Corrosion Avoidance

• Corrosion can be avoided by creating a barrier between the metal and oxygen-containing substances.
• Methods include:
  • Painting
  • Electroplating
  • Galvanising
  • Sacrificial protection
  • Alloying
  • Passivating

Decomposition

• Decomposition is the breakdown of a substance into two or more substances.
• Most decomposition processes require energy to initiate.
• Thermal decomposition is a type of decomposition that requires heat energy.

Heat Transfer

• Conduction is the transfer of heat through direct contact between molecules.
• Convection involves the transfer of heat through the movement of fluids (liquids and gases).
• Radiation involves the transfer of heat through electromagnetic waves.

Waves

• Waves are disturbances that transfer energy without transferring matter.
• Electromagnetic waves are a form of radiation that can travel through a vacuum.
• Mechanical waves require a medium to travel.
• Transverse waves can move through both matter and a vacuum while longitudinal waves require a medium.