📚 Topic Summary
Refrigerators use thermodynamic principles to transfer heat from a cold reservoir (inside the fridge) to a hot reservoir (the kitchen). This process requires work, usually supplied by an electric motor. The efficiency of a refrigerator is described by its coefficient of performance (COP), which is the ratio of heat removed from the cold reservoir to the work input. Understanding the refrigeration cycle, involving evaporation, compression, condensation, and expansion, is key to understanding how these appliances keep our food cold.
In essence, refrigerators don't just cool things down; they actively move heat against its natural tendency to flow from hot to cold. This seemingly simple process is governed by the laws of thermodynamics and cleverly engineered components.
🧮 Part A: Vocabulary
Match the following terms with their definitions:
| Term |
Definition |
| 1. Evaporator |
A. The component where high-pressure refrigerant turns into a liquid, releasing heat. |
| 2. Condenser |
B. A measure of a refrigerator's efficiency, calculated as heat removed divided by work input. |
| 3. Compressor |
C. The component where refrigerant absorbs heat and turns into a gas. |
| 4. Expansion Valve |
D. A device that reduces the pressure of the refrigerant before it enters the evaporator. |
| 5. Coefficient of Performance (COP) |
E. A pump that increases the pressure and temperature of the refrigerant. |
(Answers: 1-C, 2-A, 3-E, 4-D, 5-B)
✍️ Part B: Fill in the Blanks
A refrigerator works by moving heat from a ______ space to a ______ space. This process is driven by a refrigerant that cycles through four main components: the evaporator, _______, condenser, and expansion valve. The efficiency of the refrigerator is measured by the _______, which indicates how much heat is removed for each unit of work done. The entire cycle is based on the laws of ______.
(Answers: cold, warm, compressor, coefficient of performance (COP), thermodynamics)
🤔 Part C: Critical Thinking
Explain how the second law of thermodynamics relates to the operation of a refrigerator. Why is it necessary to do work on the refrigerant to cool the inside of the refrigerator?