Kinetic and Potential Energy of Particles
Aligned to HS-PS3-2 — Next Generation Science Standards.
What this lesson teaches
The energy of a sample of matter is stored two ways at the particle scale: kinetic energy from the motion of the particles, and potential energy stored in the relative positions of particles bound by forces (in bonds and in fields). Adding up both kinds gives the total internal energy you observe at the macroscopic scale.
Worked example
When ice melts, the temperature stays at 0 degrees C even though heat is flowing in. The added energy does not speed the particles up (kinetic energy is steady, so temperature holds); instead it goes into potential energy, pulling water molecules apart from their fixed lattice positions into a freely moving liquid.
Practice questions
- Which kind of particle energy does temperature most directly measure?
- During melting the temperature is constant. Explain where the added energy is going in terms of kinetic and potential energy.
- Describe one everyday change in which a substance's potential energy increases while its kinetic energy stays about the same.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Energía cinética y potencial de las partículas
La energía de una muestra de materia se almacena de dos maneras a escala de partículas: energía cinética por el movimiento de las partículas, y energía potencial almacenada en las posiciones relativas de las partículas unidas por fuerzas (en los enlaces y en los campos). Sumar ambos tipos da la energía interna total que observas a escala macroscópica.
Ejemplo: Cuando el hielo se derrite, la temperatura se mantiene en 0 grados C aunque siga entrando calor. La energía añadida no acelera las partículas (la energía cinética se mantiene, así que la temperatura no cambia); en cambio, se convierte en energía potencial, separando las moléculas de agua de sus posiciones fijas en la red para formar un líquido que se mueve libremente.
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