Upon completion of this topic, learners will be able to:

• identify the systems and the surroundings in a chemical process.
• identify the ways in which energy is transferred in the chemical process.
• explain exothermic and endothermic chemical reactions.
• explain internal energy, work and heat in relation to the concept of thermodynamics.
• state the first law of thermodynamics.
• define enthalpy change.
• calculate enthalpy changes from experimental results, including the use of the relationship q = mcΔT.

Thermodynamics is the study of the relationships between heat, work, temperature, and energy.

The laws of thermodynamcis describe how the energy in a system changes and whether the system can perform useful work on its surroundings or not.

Figure 1. Illustration of a thermodynamic system and surroundings

There are three types of systems. An open system can exchange mass and energy, usually in the form of heat with its surroundings. For example, an open system can consist of a quantity of water in an open container.

A system is said to be in a certain state if T, P, V, n (observable variables) do not change with time. An equation that relates these observable variables is called an equation of state. Examples are energy, volume, pressure, etc. Functions that depend on the path are path functions. Examples are heat and work.