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

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

Prepare for the Chemistry Regents Exam: HERE

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