Internal energy

Need to know

What you need to know

• **Definition**: Internal energy (U) is the sum of the random kinetic and potential energies of a system's molecules.
• **Kinetic Energy (KE)**: Related to the motion of particles. An increase in temperature leads to an increase in the average KE of the particles.
• **Potential Energy (PE)**: Related to the intermolecular forces between particles and their separation. PE changes significantly during a phase change (e.g., melting or boiling).
• **Temperature Link**: For any substance, increasing its temperature increases the random kinetic energy of its particles, thus increasing its internal energy.

Explanation

Internal energy

1. **Definition**: Internal energy (U) is the sum of the random kinetic and potential energies of a system's molecules.
2. **Kinetic Energy (KE)**: Related to the motion of particles. An increase in temperature leads to an increase in the average KE of the particles.
3. **Potential Energy (PE)**: Related to the intermolecular forces between particles and their separation. PE changes significantly during a phase change (e.g., melting or boiling).
4. **Temperature Link**: For any substance, increasing its temperature increases the random kinetic energy of its particles, thus increasing its internal energy.