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Unit 8: Thermodynamics and Thermochemistry
Guiding Questions:
- What is energy?
- How do we measure energy?
- Why are some things more explosive than others?
- Can any reaction occur?
- If everything tends toward lower energy what does that predict about the future of the universe?
What you should learn:
- Energy can neither be created nor destroyed only transformed from one form into another. If an object loses energy something else must gain an equivalent amount of energy and that change in energy will result in changes in the molecules; their motion (kinetic energy) and/or potential energy.
- The motion of molecules and atoms explains energy transfer and changes in volume and pressure.
- Whether or not a reaction requires a consistent input of energy depends on two factors - the change in potential energy and the change in entropy (energy dispersal).
- The natural tendency in the universe is for a decrease in energy and an increase in entropy.
More Specifically...:
IB Objectives: SL
HL
- Enthalpy, Energy, Heat
- Classify the various forms of energy: potential, kinetic, and mass-energy etc.
- Distinguish between heat and temperature.
- Compare the specific heat capacities of two substances in terms of
- a. strength of intermolecular forces and
- b. which requires more energy to change the temperature
- Define
- a. Standard enthalpy of formation
- b. Heat of reaction
- c. Heat of combustion
- d. Heat of vaporization
- e. Heat of fusion
- f. Standard enthalpy of reaction I
- g. Average bond enthalpy
- Phase Changes
- Describe how energy is gained or lost during changes of state
- Write and interpret thermochemical equations for phase changes
- Calculate enthalpy change for phase changes using heat of vaporization and heat of formation
- State that the temperature of a substance does not change as it undergoes a change in state
- Determine when to use q = mC?T and when to use q = m?H
- Graph and interpret a heating/cooling curve Help
- Chemical Change
- Draw and interpret energy diagrams
- Deduce the relative stabilities of reactants and products and the sign of the enthalpy changes for the reaction
- Describe and explain the changes which take place at the molecular level in chemical reactions IBH 6.1.4
- Relate bond formation to the release of energy and bond breaking to the absorption of energy.
- Write and interpret thermochemical equations for chemical reactions
- Use enthalpy change to classify reactions as exothermic and endothermic reactions.
- Calculate enthalpy change using
- a. Energy diagrams
- b. Calorimetry
- c. Calorimetry with stoichiometry
- c. Hess's Law (construct simple enthalpy cycles)
- d. Heats of formation
- e. Bond enthalpies
- Suggest suitable experimental procedures for measuring enthalpy changes of reactions in aqueous solution
- Define entropy and determine whether an increase or decrease in entropy occurs for a given reaction.
- a. Mixtures, change in state, particle movement, number of particles
- b. Number of particles has a greater affect than other factors
- Define spontaneous
- State that negative values of ?H and positive values of ?S are associated with spontaneous reactions
- Define standard free energy change for a reaction
- Calculate Gibbs Free Energy to identify spontaneous reactions
- Compare and contrast various possible sources of energy and the consequences to the environment of using these sources
Lecture Notes:
Assignments:
Labs:
Resources:
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