Internal energy facts for kids
The internal energy of something, like a body or a system, is all the energy hidden inside it. Think of it as the total energy of all the tiny particles that make up that body.
This energy includes:
- The kinetic energy from the movement of molecules. Molecules are always wiggling, spinning, and moving around.
- The potential energy stored in the connections between atoms within molecules or crystals. This is like the energy stored in a stretched spring.
- The energy found in all the chemical bonds.
- The energy of free electrons, especially in metals.
Internal energy is a special kind of energy that helps us understand how systems behave. It's measured in joules (J), which is the standard unit for energy. You might also hear about calories, especially when talking about food, but those are usually kilocalories (1000 calories).
What Internal Energy Is Not
Internal energy is only about the energy *inside* an object. It does not include:
- The energy of the whole object moving from one place to another (like a ball rolling).
- The energy of the whole object spinning (like a spinning top).
- The energy an object has because of its position in an outside gravitational field (like a ball held high up) or an electric field.
However, it does include energy related to how the object is squished or stretched, or how its tiny particles respond to electric or magnetic fields.
How Particles Contribute
Every tiny particle in a substance has energy. This energy comes from different types of motion:
- Translational motion: This is when particles move from one place to another, like tiny billiard balls.
- Rotational motion: This is when particles spin around their own center.
- Vibrational motion: This is when particles wiggle back and forth, like a spring.
For very simple substances, like helium gas, the atoms are so small and simple that their internal energy mostly comes from just their translational motion. They don't really spin or vibrate much.
Scientists use statistical mechanics to understand how all these tiny movements and stored energies add up to the total internal energy of a system.
See also
In Spanish: Energía interna para niños
