{"id":1737,"date":"2023-10-24T22:58:09","date_gmt":"2023-10-25T05:58:09","guid":{"rendered":"http:\/\/www.autodesk.com\/products\/eagle\/blog\/?p=1737"},"modified":"2025-08-06T12:06:12","modified_gmt":"2025-08-06T19:06:12","slug":"three-laws-thermodynamics","status":"publish","type":"post","link":"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/three-laws-thermodynamics\/","title":{"rendered":"Three Laws of Thermodynamics & Entropy Explained"},"content":{"rendered":"\n

Explore the three laws of thermodynamics: energy conservation, the law of entropy, and absolute-zero behavior. Plus real-life examples that make these thermodynamics laws easy to grasp.<\/em><\/p>\n\n\n\n

Everything is thermodynamics. This isn\u2019t just a concept reserved for the realm of physics, and it\u2019s not a set of laws that you\u2019ll only find in electronics, refrigerators, cars, planes, etc. This is a scientific concept that weaves itself into the very fabric of life. <\/span><\/p>\n\n\n

What are the Laws of Thermodynamics?<\/h2>\n\n\n

The laws of thermodynamics describe how energy, heat, and entropy behave in physical systems. The zeroth law defines thermal equilibrium. The first law states energy cannot be created or destroyed, only transformed. The second law says entropy increases over time. The third law states entropy approaches zero as temperature nears absolute zero.<\/p>\n\n\n\n

Let’s take a deep dive into each below.<\/p>\n\n\n

The Three Laws of Thermodynamics: Energy, Entropy & Equilibrium<\/h2>\n\n\n

The problem is, that thermodynamics is just the way energy works, so it\u2019s easy to miss. When you clean your office week after week, which seems to get messier by the day, that\u2019s the Second Law of Thermodynamics at work. Everything leads to an increased state of disorganization. <\/span><\/p>\n\n\n\n

Or when you cook that delicious steak on the grill this weekend, that\u2019s the First Law of Thermodynamics at work. Energy is transferred in the form of heat to your food. Thermodynamics is not just the study of heat and work. It\u2019s the study of how energy, the stuff that you and I and everything around you are made of, works. <\/span>Thermodynamics is the study of life.<\/p>\n\n\n

Systems and surroundings<\/h2>\n\n\n

We all live in a system where matter and energy are being continuously exchanged; it\u2019s an endless flow. Take, for example, the process of eating. You take in the chemical energy of food and convert it into a form that can be used by your body. Now that your body has energy gained from food, it can go about doing work out in the world.<\/span><\/p>\n\n\n\n

This process of exchange, where energy transforms from one state to another all happens within a set of <\/span>systems and <\/span>surroundings. When you turn on your electric tea kettle in the morning, you have water enclosed within a metal container; that\u2019s your system. The rest of the kitchen and even the rest of the house are the surroundings.<\/span><\/p>\n\n\n\n

\"thermodynamic-system\"
Every thermodynamic system is surrounded by a boundary and surroundings. (Image source<\/a>)<\/em><\/figcaption><\/figure>\n\n\n\n

When your tea kettle starts to boil, it transforms some of the water into steam which releases from the spout at the top. This converted energy crosses a <\/span>boundary from the system within the metal container to the surroundings outside of it. This is thermodynamics at work\u2014the transference of energy and matter between systems and surroundings<\/span>.<\/p>\n\n\n

What are systems and surroundings?<\/h3>\n\n\n

Systems are defined by the observer. So, to one person, the tea kettle might be the system. To another, the entire house might be the system, and the neighborhood the surroundings. It all depends on your perspective. The point is that every system in thermodynamics is contained within a defined boundary, and on the other side of the boundary are the surroundings. There are three types of systems in thermodynamics:<\/span><\/p>\n\n\n\n