Now try defining the system and surroundings in some new situations, which do not involve refrigerators.
Worked Example
Look at the image below.
- A propane fueled Bunsen burner is used to warm a container of water. Define the system and the surroundings, assuming that we wish to focus on the warming of the water.
- Describe the direction of energy flow based on your definitions in part A.
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- In this situation, it is reasonable to define the system to be the water inside the container. Then, the surroundings are composed of everything external to the water, including the walls of the container itself.
- Based on the definition that the water is the system, energy is transferred from the surroundings to the system.
Your Turn
Consider what the system and surroundings are in the following image.
- Define the system and the surroundings, assuming that we wish to focus on the warming of the water.
- Describe the direction of energy flow based on your definitions in part A.
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- In this situation, it is most reasonable to define the system to be the water inside the container. The surroundings are everything besides the water, including the heating coil that is immersed in the water. Even though the heating coil is completely surrounded by the system, the coil itself is part of the surroundings.
- Since the system is only composed of the water and the water absorbs energy, the direction of energy transfer is from the surroundings to the system. The fact that the heating coil is immersed in the water does not change this description. Eventually, however, energy will also begin to flow from the system to the surroundings, as the water warms and releases energy to the container wall and the surrounding air.