08-Jun-2012

Knowledge Statements

1. The total energy of a system is conserved, but it can be converted between forms, or transferred in or out of a system. 
2. Energy can be "stored" in molecular velocity, rotation, vibration, bonds and position within a “field”. 
3. Exothermic reactions involve the transfer of energy into the surrounding environment (this energy is derived from the formation of more stable bonds than existed previously, that is, the bonds in the products are more stable (on average) than the bonds in the reactants). 
4. Endothermic reactions involve the transfer of energy into the system from the environment (this energy is derived from the formation of more less bonds than existed previously, that is, the bonds in the products are less stable (on average) than the bonds in the reactants). 
5. In open systems, energy and matter can enter and leave; in closed systems matter cannot leave or enter, but energy can. In an isolated system, neither energy or matter can enter or leave. 
6. The temperature of a system is related to the average speed of the molecules (including intermolecular vibrations and rotations). 
7. Entropy is a measure the number of available states within a system. The direction of change is determined by direction in which there is an increase in total entropy (system and surroundings), that is, an increase in the number of available states.
8. The temperature at which a phase change occurs is determined by the strength of interactions between particles. 
9. The change in free energy (Gibbs energy) is a function of the total entropy change for the system and the surroundings.

Performance expectations:

• Explain the difference and relationship between temperature, thermal energy, and kinetic energy.
• Explain why particles in gases move at a range of different velocities at a given temperature. Draw Boltzmann distributions of particles at different temperatures, or for particles of different molecular weights.
• Explain the causes of water’s anomalous properties (high melting point, boiling point, density of ice relative to liquid water, specific heat)
• Relate the heat capacity of a particular substances to its molecular-level structure.
  
• Draw heating or cooling curves showing how temperature changes when thermal energy is added to a substance (including a phase change). Explain why temperature does not change during a phase change.
• Construct a model or diagram of open, closed and isolated systems.
• Explain the difference between state and path functions and give examples.
• For exothermic and endothermic processes, and phase changes, identify the direction of thermal energy change and the sign of q or ΔH for the system and the surroundings.
• For exothermic and endothermic processes, and phase changes, identify whether the number of available states (i.e. entropy) in the system and surroundings increase or decreases.
• Use ΔG or the total entropy change to predict whether a process is thermodynamically favorable.