Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Heat (q) is the transfer of thermal energy between two bodies due to a temperature difference. It flows from a hotter object to a cooler one.
5 Must Know Facts For Your Next Test
Heat is measured in joules (J) or sometimes in calories (cal).
The first law of thermodynamics states that the change in the internal energy of a system is equal to the heat added to the system minus the work done by the system: $$\Delta U = q - w$$.
Heat can be transferred through conduction, convection, and radiation.
In an exothermic process, heat is released by the system into its surroundings; in an endothermic process, heat is absorbed by the system from its surroundings.
Specific heat capacity ($c$) is a property that indicates how much heat is required to raise the temperature of one gram of a substance by one degree Celsius.
A measure of the average kinetic energy of particles in a substance. It determines the direction of heat transfer.
$\Delta H$ (Enthalpy Change): The total heat content change in a chemical reaction at constant pressure. It indicates whether a process is exothermic or endothermic.
$c$ (Specific Heat Capacity): The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.