Basics of Thermodynamics

What Is Thermodynamics?

Thermodynamics is the science that studies how heat and energy move and change in the universe.

It explains how heat flows from warmer things to cooler ones.
The First Law of Thermodynamics: Energy cannot be created or destroyed — only changed (like from heat to motion).

Internal Energy (U): Energy stored in the movement of atoms and molecules of all substances
Formula: ΔU = Q − W

Thermodynamics helps explain real-world machines, weather, and even how your body works!

The Second Law of Thermodynamics: Heat naturally flows from hot to cold, unless energy is added to reverse it.

Real-World Examples:
- Your body uses thermodynamics to stay warm by shivering and cool down by sweating.
- Refrigerators: They use refrigerant fluid and a compressor to pull heat from the inside and release it outside.
- Charging a phone: Electrical energy is stored in the battery, but some is lost as heat, causing the phone to warm up.

Here are some interesting facts about thermodynamics:

Black holes follow the laws of thermodynamics, too!
A microwave heats food using radiation, causing water molecules to vibrate and create heat from the inside out!
Car engines turn only about 30% of fuel energy into motion—the rest is lost as heat!
The coldest possible temperature, absolute zero (–273.15°C), is when particles stop moving completely!

Let’s quickly recap what we learned about the basics of thermodynamics:

What law says energy cannot be created or destroyed? First Law of Thermodynamics
What do fridges move out to keep things cold? Heat
What is the energy stored in the movement of atoms and molecules? Internal Energy
What does the Second Law of Thermodynamics say about how heat flows? From Hot to Cold