Regents Chemistry Review By Topic: Energy And Heat

Endothermic - energy is absorbed in the reaction

Exothermic - energy is released in the reaction.

Heat is the transfer of energy from hotter to colder object. The letter for heat is q.

Table T gives 3 equations for heat.

We use q=mCΔT when the question mentions specific heat capacity or where there is a change in temperature. ΔT = Tfinal- Tinitial

We use q=mHf when there is a phase change between solid and liquid (either solid turning into liquid or liquid turning into solid.

We use q=mHv where there is a phase change between liquid and gas.

If the question talks about water, Table B gives all the constants we need to know about water including specific heat capacity (C), Hf and Hv.

Heating Curve Diagram

heating curve diagram
  • When the line is slanted, kinetic energy increases and potential energy stays the same

  • When the line is straight horizontally, potential energy increases and kinetic energy stays the same

  • To find the melting point, find the solid/liquid segment and go to the left to see what temperature it is at

  • To find the boiling point, find the liquid/gas segment and go to the left to see what temperature it is at

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