Free energy is used to determine if the reaction is spontaneous at a specific temperature.Ī chemical reaction that can proceed in both directions is called a reversible reaction. Free energy (G) relates temperature, enthalpy and entropy. Temperature can determine whether a process is spontaneous. Spontaneity occurs without outside intervention. Second law of thermodynamics states that every spontaneous process has an increase in entropy of the universe. When changing between solids, liquids and gases, the temperature does not change. Heat capacity is the amount of energy that can be absorbed by a particle, before the temperature increases. In exothermic reaction, the system gives off energy to the surroundings. In endothermic reaction, the system takes in energy from the surroundings. Enthalpy of reaction is the net energy change during a chemical reaction. Under constant pressure, heat and enthalpy are the same. Heat is the flow of energy from higher temperature particles to lower temperature particles.Įnthalpy (H) takes into account the internal energy of the sample along with pressure and volume. Energy can be transferred through work applying a force over a distance.Įnergy changes of physical and chemical processesįirst law of thermodynamics states that energy can not be created or destroyed in physical or chemical changes. Joules (J) and calories (cal) are the most common energy units. Increased temperature increases molecular motion.