Physical properties · Hebden reference
Reference material for physical properties, vapour pressure, melting and boiling. Follow the separate teacher instructions for any lab.
Physical properties
A physical property can be observed without changing chemical identity. Density does not depend on the amount of a substance; total mass does. Classify using the property being measured.
Vapour pressure and boiling
Particles escape from a liquid and can return to it. In a closed container at equilibrium, evaporation and condensation have equal rates. Boiling begins when vapour pressure equals external pressure.
Phase changes on a graph
Read axes and conditions first. In an idealized heating curve for a pure substance at fixed pressure, a flat region represents a phase change: energy changes particle arrangement while temperature remains roughly steady.