AP Chemistry Unit 5: Thermodynamics Quiz

AP Chemistry Unit 5: Thermodynamics

• Test Format: 4-6 free response questions, 30-35 multiple choice questions
• Material Covered: Thermodynamics (80%), Stoichiometry, bonding, atomic, and reactions (20%)
• Study Resources: Practice free response questions, notes, homework, quizzes, reference sheets, and chemical reactions/atomic/bonding review assignments.

Heat vs. Temperature

• Heat: Transfer of thermal energy between systems measured in Joules (J) or Calories (cal).
• Temperature: Measures the average kinetic energy (KE) of particles within a substance, expressed in Fahrenheit, Celsius, or Kelvin.
• Relationship: When average KE doubles, Kelvin temperature also doubles. Kelvin is directly proportional to average KE.

Boltzmann Distribution

• Probability: Describes the probability of a system being in a particular state.
• Kinetic Energy Distribution: Displays the distribution of kinetic energy (KE) for a set of molecules at a given temperature.
• Molecular Collisions: Some particles collide and are deflected with high speeds, others nearly stop; some molecules reach a minimum activation energy (Ea) before reacting with the correct orientation.

Activation Energy (Ea)

• Definition: Minimum energy needed for a reaction to occur. It's the energy needed for molecules to collide with the correct orientation and form a transition complex.
• Transition Complex: Represents the unstable state where bonds are breaking and forming during a reaction.
• Examples: For a reaction to happen, molecules need to reach a certain activation energy threshold. Matches remain unlit without a spark and sunlight can break down substances in brown bottles.

Heat Transfer

• Conduction: Heat transfer between two systems in contact until thermal equilibrium is reached.

Conservation of Energy

• First Law: Energy cannot be created or destroyed.
• Change in Systems: Energy changes during chemical reactions and phase changes.

Endothermic vs. Exothermic Systems

• Endothermic: Systems absorb heat from the surroundings, products have greater potential energy than reactants
• Exothermic: Systems release heat to the surroundings, products have lower potential energy than reactants

Enthalpy (ΔH)

• Definition: Total internal energy of a system (sum of potential and kinetic energy).
• Extensive Property: Depends on the amount of substance.
• Intensive Property: Does not depend on the amount of substance.

Bond Enthalpy

• Average amount of energy needed to break a chemical bond

Specific Heat

• Heat energy required to raise the temperature of 1 gram of substance by 1°C (or 1 K). It measures a substance's ability to absorb or retain heat.

Calorimetry

• Techniques used to measure heat changes
• Quantifies the total heat transfer (q) given mass (m), specific heat (C), and change in temperature (ΔT)

Coffee Cup Calorimetry

• Measures heat transfer/exchange in aqueous reactions within a closed system

System vs Surroundings

• System: Specifies the specific process taking place
• Surroundings: Specifies area outside of the process

Gibbs Free Energy (ΔG)

• Equation: ΔG° = ΔH° - TΔS°
• Free Energy: Energy available to do work in a chemical reaction or process.
• ΔG < 0: Process can happen spontaneously.
• ΔG > 0: Process won't happen on its own, outside energy is needed.

Entropy (S)

• A measure of disorder in a system
• Measured in J/K mol
• Increased entropy leads to increase in microstates, a measure of possible arrangements of particles
• Entropy increases during heat absorption, chemical decomposition reactions, dissolution processes, phase transition processes(such as melting or vaporization), most chemical reactions

Test your understanding of thermodynamics in AP Chemistry Unit 5, which covers essential concepts such as heat, temperature, and Boltzmann distribution. This quiz includes various question formats to assess your grasp of key ideas and relationships in physical chemistry.