Thermochemistry and Chemical Bonding Fundamentals

Posted on Feb 18, 2025 in Chemistry

Thermochemistry and Chemical Bonding

Vaporization Heat: The amount of heat needed to convert 1 mol of a liquid substance to gas.
Melting Point: A constant temperature where a balance exists between the liquid and solid phases.
Boiling Point: A constant temperature where a balance exists between the gas and liquid phases.
Freezing Point: A constant temperature where equilibrium exists between the liquid and solid phases.
Heat of Reaction (Enthalpy): The amount of heat absorbed or released during a chemical reaction.
Thermochemistry: The study and measurement of energy transferred as heat during chemical reactions.
Heat: Energy transferred from one place to another due to temperature differences.
Temperature: A physical unit measuring the degree of heat between two bodies in thermal contact.
Endothermic Reaction: A reaction that absorbs heat.
Exothermic Reaction: A reaction that gives off heat.
Calorie: A unit of heat defined as the amount of heat needed to raise the temperature of 1 gram of water from 14.5°C to 15.5°C.
Specific Heat (Ce): A constant of proportionality for pure substances; the amount of heat needed to raise the temperature of 1 gram of a substance by 1°C.
- Ce H₂O (s): 0.49 cal/g*°C
- Ce H₂O (l): 1 cal/g*°C
- Ce H₂O (g): 0.48 cal/g*°C

Fusion: The process where a substance changes from solid to liquid.
Boiling (Evaporation): The process where a substance changes from liquid to gas.
Condensation: The process where a substance changes from gas to liquid.
Freezing: The process where a substance changes from liquid to solid.
Heat of Fusion: The amount of heat needed to convert 1 mol of a solid substance to liquid.
Heat of Vaporization: The amount of heat needed to convert 1 mol of liquid to gas.

Heat or Molar Enthalpy of Formation: The enthalpy change accompanying the formation of one mole of a substance from its elements at 1 atmosphere and 25°C.
Heat or Enthalpy of Decomposition: The enthalpy change accompanying the decomposition of 1 mole of a substance into simpler substances.
Heat or Molar Enthalpy of Combustion: The amount of heat released when burning one mole of a substance at 1 atmosphere and 25°C.

Hess’s Law: The heat produced in a chemical reaction at constant pressure is the same whether the reaction occurs directly in one step or indirectly in multiple steps.
Calorimeter: An instrument used to measure the heat of reaction in an isolated system.

Chemical Bonding: The force that holds atoms together in a compound.
Octet Rule: Atoms accept, donate, or share electrons to achieve a noble gas configuration (8 valence electrons) in their outer shell.
Ionic (Electrovalent) Bond: A bond between metallic and nonmetallic elements formed by transferring electrons, creating ions.
Covalent Bond: A bond between nonmetals formed by sharing electrons.
- Polar Covalent Bond: Between different atoms.
- Nonpolar Covalent Bond: Between identical atoms.
Lewis Structure: A graphical representation of valence electrons in a chemical bond using dots.
Dative Bond: A bond where one atom contributes a pair of electrons to another atom.
Periodic Table: The arrangement of chemical elements into groups with similar physical and chemical properties.
Resonance: Equivalent structures of an ion or molecule showing different ways of linking atoms while fulfilling the octet rule.
Hydrogen Bond: Additional attractive forces between polar molecules containing hydrogen atoms.