The scientific discipline of chemistry includes a branch called thermodynamics that observes the changes that take place with different forms of energy. In this branch, the concepts of system and surroundings are used repeatedly.
A system, in thermodynamics, is simply something a scientist is interested in studying. It can be something as simple as a beaker in which an experiment is being run with a solution contained within it or something as complex as a space shuttle. The surroundings are everything outside the system and are the place where the observation and measurements of the system are taken. For example, a chemist may be studying the amount of heat evolved (released) during a reaction in a beaker. The beaker is the system and the surroundings are everything else, including the lab where the chemist takes measurements.
Together, these two concepts make up what is called the universe. There are three types of systems: open, closed, and isolated. In an open system, both matter and energy (heat) can be exchanged between the system and its surroundings. Many of the machines we see around us today are open systems, such as cars. Both energy and matter can be exchanged between the car (the system) and its surroundings in the form of heat (energy) and gasoline (matter).
In a closed system, only energy can be exchanged between the system and its surroundings, meaning that no matter can transfer between the two. A bomb calorimeter is an example of a closed system often found in chemistry laboratories. No matter is exchanged with the surroundings, but when igniting the fuse to burn the sample under study, energy must travel into the system.
In an isolated system, neither matter nor energy can pass between the system and surroundings. These systems are purely theoretical, as there is always some energy exchange with systems and surroundings. The universe as a whole is one example of an isolated system because there is nothing with which it can exchange either energy or matter.
These two concepts are the foundations of thermodynamics. Without defining ‘system’ and ‘surroundings,’ it would be impossible to quantitatively measure the exchange of energy that occurs in all of the processes in the universe. Using these definitions, chemists can study the energy changes that take place in chemical reactions in a laboratory, allowing them to harness energy necessary to produce work to enhance our lives.