B

Boiling Point

P_vapour = P_external (at T_b)
Quick Reference
Formula / NotationP_vapour = P_external (at T_b)
Also Known AsBoiling temperature, vaporisation point, normal boiling point (at 1 atm)

What is Boiling Point?

The boiling point of a liquid is the temperature at which its vapour pressure equals the atmospheric pressure, causing the liquid to vaporise throughout its volume. The normal boiling point is measured at 1 atm (101.325 kPa). Boiling point depends on the strength of intermolecular forces and applied pressure; substances with stronger intermolecular forces have higher boiling points.

Formula & Notation

P_vapour = P_external (at T_b)

Other Names / Synonyms: Boiling temperature, vaporisation point, normal boiling point (at 1 atm)

Properties & Characteristics

The boiling point is the temperature at which the vapour pressure of a liquid equals the surrounding atmospheric pressure, and the liquid undergoes bulk vaporisation. The normal boiling point is defined at 1 atm (101.325 kPa). It depends on intermolecular forces: substances with strong hydrogen bonds (water, 100°C) boil higher than those with only London dispersion forces. Boiling point decreases with reduced external pressure.

Uses & Applications

Boiling points are used to characterise and identify substances, design separation processes (fractional distillation), set process temperatures in chemical engineering, and determine the boiling points of mixtures using Raoult's law. They are key data in thermodynamic databases.

Safety Information

Boiling liquids pose serious burn hazards from hot vapour and splashing. Superheating (heating liquid above its boiling point without nucleation) can cause explosive bumping; add boiling chips to prevent this. Always use heat-resistant glassware rated for the temperature involved.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Boiling Point
Formula P_vapour = P_external (at T_b)
Synonyms Boiling temperature, vaporisation point, normal boiling point (at 1 atm)

Frequently Asked Questions

The boiling point of a liquid is the temperature at which its vapour pressure equals the atmospheric pressure, causing the liquid to vaporise throughout its volume. The normal boiling point is measured at 1 atm (101.325 kPa). Boiling point depends on the strength of intermolecular forces and applied pressure; substances with stronger intermolecular forces have higher boiling points.

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