therm-

Quick Definition

Meaning: Heat or temperature

Origin: Greek (therme = heat)

Pronunciation: THERM

Why It Matters

Therm- is a root that appears in thermodynamics, thermochemistry, and dozens of everyday scientific terms. The most important distinction for students is between exothermic and endothermic reactions. Exothermic releases heat to the surroundings (the system loses energy), while endothermic absorbs heat (the system gains energy). A common mistake is thinking exothermic means 'hot' — it doesn't. It means heat is leaving the system. An exothermic reaction can still feel cold if the surroundings absorb the heat quickly. The sign convention is critical: in thermodynamics, we typically define q (heat) as positive when heat enters the system (endothermic) and negative when heat leaves (exothermic). This is opposite to how we intuitively think about 'releasing heat.' Another critical term is thermodynamically favorable, which means a reaction has a negative Gibbs free energy change. This doesn't guarantee the reaction will happen quickly — that's kinetics, not thermodynamics. Diamond converting to graphite is thermodynamically favorable but kinetically so slow that it effectively never happens. When you see therm-, always ask: is heat going in or coming out?

Examples

• Exothermic
• Endothermic
• Thermodynamics
• Thermochemistry

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