---
title: "Energy can't be created or destroyed"
description: "Explain the principle of conservation of energy (energy cannot be created or destroyed, only transferred between stores), and describe how energy is dissipated as thermal energy to the surroundings in"
canonical: https://lightmysky.com/learn/science/energy-cant-be-created-or-destroyed-mt_68pIoiiG4g
source: https://lightmysky.com/learn/science/energy-cant-be-created-or-destroyed-mt_68pIoiiG4g.md
retrieved: 2026-10-19
---

> **Agent view.** This is the Markdown twin of the page, for tools and assistants.
> When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md
> API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md
> Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt
> Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json
> Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`.

# Energy can't be created or destroyed

Explain the principle of conservation of energy (energy cannot be created or destroyed, only transferred between stores), and describe how energy is dissipated as thermal energy to the surroundings in all real processes

Subject: Science · Area: Energy · Ages 11 to 12
Page: https://lightmysky.com/learn/science/energy-cant-be-created-or-destroyed-mt_68pIoiiG4g

## Ready when they can

- States the law of conservation of energy
- Explains that an isolated system's total energy stays constant because no energy enters or leaves, even when its stores change
- Explains dissipation and identifies causes such as friction, air resistance and electrical resistance
- Gives an example showing why 'wasted' energy is not lost but transferred to the surroundings

## Lesson: Energy can't be created or destroyed

Energy cannot be created or destroyed. Energy can remain stored without changing stores or form. An isolated system exchanges no energy with its surroundings, so its total stays constant. Energy can leave an object without being destroyed. In an energy account, input plus decreases in stores equals output plus increases in stores. A discharging battery can supply output by reducing its chemical store. Include the surroundings when energy leaves the object.

*(drawing: Model: only the battery chemical store increases; the remaining input goes to surroundings. Subtract that transfer from input.)*

Dissipation means energy spreads into thermal stores and becomes less available for the intended job. It is harder to collect and reuse, not destroyed. Friction, air resistance and electrical resistance can cause this spreading.

**Example.** Electrical resistance warms parts in a charger or motor. A motor can also warm through friction between moving parts. The warmer parts then transfer energy to cooler surroundings. A charger does not need moving parts to warm up.

**Example.** A fuel-burning engine heats its parts and exhaust gases. Friction also warms moving parts. These transfers leave less energy for useful motion. Air resistance acts on the moving vehicle, not on the engine alone. None of this energy is destroyed.

**Example.** A bouncing ball transfers energy to thermal stores in the ball and floor, and sound carries energy away. Less remains in its motion and height stores, so later bounces are lower. The ball can lose energy while the total including surroundings is conserved.

**Example.** Bike brake pads rub against a wheel or brake disc. Friction reduces the bike's kinetic store and increases thermal stores in the brakes. The brakes then heat their surroundings. The kinetic energy has been transferred, not destroyed.

**Recap.** Energy is conserved when all stores and transfers are counted. An isolated system exchanges no energy. Dissipation spreads energy into thermal stores, making it less available for the intended job.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Naming types of energy](https://lightmysky.com/learn/science/naming-types-of-energy-mt_akBotspaf2)
- [Energy stores and transfers](https://lightmysky.com/learn/science/energy-stores-and-transfers-mt_Jvg_r4yWaY)

## Opens up

- [Power: watts and energy per second](https://lightmysky.com/learn/science/power-watts-and-energy-per-second-mt_ckpA3oZQ44)
- [Efficiency, Sankey diagrams, and work done](https://lightmysky.com/learn/science/efficiency-sankey-diagrams-and-work-done-mt_JyfLtl_nhw)
- [Reactions That Release or Absorb Heat](https://lightmysky.com/learn/science/reactions-that-release-or-absorb-heat-mt_UoqUPI_uNz)