Closed system

A system, which can exchange energy but not mass with the surroundings is called a closed system. For example, boiling water in a closed steel vessel is an example of a closed system. The energy can be gained or lost (through the steel walls) but not matter. Similarly, all reactions carried out in a closed container are examples of closed systems.

Open system

A system, which can exchange matter as well as energy with the surroundings is called an open system. All reactions carried out in open containers are examples of open systems. Evaporation of water in a beaker or hot coffee in a cup represents an open system. Here vapour of water or coffee (matter) can leave the system and escape into atmosphere. The heat energy required for this purpose is absorbed from the surroundings. All physical and chemical processes taking place in open in our daily life are open systems because they are continuously exchanging matter and energy with the surroundings.

a) Open system

A system, which can exchange matter as well as energy with the surroundings is called an open system. For e.g., hot coffee in an open flask because it can gain or loose matter and energy with the surroundings.

fig 4.1 - Example of open system

b) Closed system

A system, which can exchange energy with the surroundings but not mass is called a closed system. For e.g., calcination of CaCO3 taken in sealed bulb. On heating, CaCO3 decomposes into CaO and CO2, however, CO2 cannot escape and remains trapped in the bulb.

fig 4.2 - Example of closed system

c) Isolated system

A system, which can neither exchange mass nor energy with the surroundings is called an isolated system. For e.g., a reaction carried out in a closed, well insulated container (such as thermos flask).

fig 4.3 - Example of an isolated system