Isn’t it surprising that a refrigerator works in such a way that the internal space stays cold while the external part is hot at the same time?
First of all, what is thermodynamics? Thermodynamics is all about how heat and other forms of energy move around, change form, and interact with the world at a super tiny level.
So how does this relate to our case study, which is the refrigerator, and how do these principles work? To understand how it works, let’s think about some simple rules of how things get hot and cold. These rules are called the laws of thermodynamics.
First Law of Thermodynamics
Law of Energy Conservation: Energy cannot be created or destroyed; it can only be transferred or changed from one form to another.
Think of this like a rule that says energy can’t just appear or disappear; it can only move around. Imagine you have a toy that you can wind up to make it move. The energy you use to wind it doesn’t disappear; it makes the toy go. In a refrigerator, the energy comes from electricity, and it moves around to make the inside of the fridge cold.
Second Law of Thermodynamics
Entropy and Direction of Heat Transfer: Heat naturally flows from a hotter object to a cooler one, and not the other way around, unless external work is performed. This law also introduces the concept of entropy, stating that the total entropy of an isolated system can never decrease over time; it can only stay the same or increase.
This rule says that heat always likes to move from hot things to cold things. Think of it like if you have a cup of hot chocolate and you put an ice cube in it. The ice melts because the heat from the chocolate goes into the ice. In a fridge, we trick the heat into moving out of the fridge so it stays cold inside.
How the Refrigerator Works
1. Inside the fridge, there’s a special liquid called a refrigerant. This liquid is like the transporter that helps move the heat out of the fridge.
2. The refrigerant starts off cold and travels through the inside of the fridge, soaking up the heat from your food.
3. Then, it travels to the back of the fridge, where it gets squeezed really tight. When it gets squeezed, it becomes hot and turns into a gas.
4. This hot gas then goes through coils at the back of the fridge, where it releases all its heat to the air outside the fridge (this is like the ice cube melting in hot chocolate).
5. Finally, the refrigerant cools down again and turns back into a liquid, ready to start the journey all over again.
So, the refrigerator uses the energy (first law) from electricity to keep moving the heat out of the inside of the fridge to the outside (second law), making sure your food stays cold and fresh.
