Joule
| Formula / Notation | 1 J = 1 kg·m²/s² = 1 N·m = 1 W·s; SI unit of energy |
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| Also Known As | J, joule (SI energy unit), newton-metre, watt-second |
What is Joule?
The SI unit of energy, work, and heat, symbol J. One joule equals the work done by a force of one newton over a displacement of one metre. In thermochemistry, energy changes are typically expressed in joules or kilojoules (kJ). Named after physicist James Prescott Joule.
Formula & Notation
Other Names / Synonyms: J, joule (SI energy unit), newton-metre, watt-second
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
The SI unit of energy, work, and heat, symbol J. One joule equals the work done by a force of one newton over a displacement of one metre. In thermochemistry, energy changes are typically expressed in joules or kilojoules (kJ). Named after physicist James Prescott Joule.
Joules are used in all thermochemical calculations (ΔH, ΔG, ΔS), in expressing activation energies (Ea in kJ/mol via Arrhenius equation), in calorimetry (specific heat = J/g·K), in expressing photon energies (E = hν, in joules), and in battery energy storage (Wh = 3600 J).
No direct safety concern for the unit. Large energy releases in kilojoules per gram (explosives release 5-10 kJ/g, compared to 45 kJ/g for TNT-equivalent energy density) help quantify explosive hazard. Accurate joule-based thermodynamic data is essential for safe chemical process design.
The formula or notation for Joule is: 1 J = 1 kg·m²/s² = 1 N·m = 1 W·s; SI unit of energy