H
Heat
AllChemicals — The Online Chemical Glossary | https://allchemicals.info/chemical/478-heat
What is Heat?
Heat (Q) is a form of energy transferred between objects due to a temperature difference. Heat always flows spontaneously from a region of higher temperature to a region of lower temperature. In thermochemistry, the heat of a reaction at constant pressure equals the enthalpy change (ΔH). Heat is measured in joules (SI) or calories; 1 calorie = 4.184 joules.
Key Facts
Term
Heat
Index
All "H" terms
Frequently Asked Questions
Heat (Q) is a form of energy transferred between objects due to a temperature difference. Heat always flows spontaneously from a region of higher temperature to a region of lower temperature. In thermochemistry, the heat of a reaction at constant pressure equals the enthalpy change (ΔH). Heat is measured in joules (SI) or calories; 1 calorie = 4.184 joules.
More "H" Terms
Haber Process
N₂ + 3H₂ ⇌ 2NH₃ | ΔH = −92 kJ/mol
Hafnium
Hf
Half Cell
Half Life
Half-Cell
E = E° − (RT/nF)lnQ
Half-Life
A(t) = A₀e^(−λt); t½ = ln2/λ
Half-Reaction
Halide
X⁻ (e.g., F⁻, Cl⁻, Br⁻, I⁻)
Halogen
F₂, Cl₂, Br₂, I₂, At; Group 17; ns²np⁵ valence configuration
Halogenation
C-X + Cl₂/Br₂ (hv or AlCl₃) → C-X(halogen); EAS or radical pathway
Halogens
Hard Acid
Hard acid: small, highly charged, low polarisability (e.g., H⁺, Mg²⁺, Al³⁺)
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