Learning outcomes

Students will be able to:

• Classify processes as exothermic or endothermic by the direction of heat flow between system and surroundings, and give the sign of ΔH.
• Explain ΔH as the difference between the energy absorbed to break bonds and the energy released to form bonds.
• Compare specific heats and use q = mcΔT, including in a coffee-cup calorimeter to identify a metal and measure a heat of neutralization.
• Use Hess's Law and standard enthalpies of formation to calculate ΔH for a reaction.

Standards alignment

• HS-PS1-4 NGSS: Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.
• HS-PS3-4 NGSS: Plan and conduct an investigation to provide evidence that the transfer of thermal energy when two components of different temperature are combined within a closed system results in a more uniform energy distribution among the components in the system.
• HS-PS3-1 NGSS: Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known.

Includes

Four stages: exothermic and endothermic processes with a bond-energy model, a specific heat race, coffee-cup calorimetry (identify a metal, measure a heat of neutralization), and Hess's Law with enthalpies of formation; and a printable lab worksheet. A teacher answer key is available from Logical Home Schooling. Continue with entropy and spontaneity in Free Energy Lab.

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