Phase Diagram — Definition, Formula, Properties & Uses | AllChemicals | AllChemicals

Also Known As	Phase diagram, P-T diagram, state diagram, stability diagram

What is Phase Diagram?

A graph showing the physical states of a substance as a function of temperature and pressure. It contains regions for solid, liquid, and gas phases separated by boundary lines. The triple point is where all three phases coexist; the critical point is where liquid and gas become indistinguishable.

Properties & Characteristics

A phase diagram is a graph (usually pressure vs. temperature) that shows the stable state(s) of a substance or mixture under different conditions. Single-component phase diagrams show regions of solid, liquid, and gas, separated by phase boundaries. Key features: triple point (T_tp, P_tp: all three phases in equilibrium), critical point (T_c, P_c: liquid-vapour distinction disappears), and normal boiling/melting points (at 1 atm). The slopes of phase boundaries are determined by the Clausius-Clapeyron and Clapeyron equations.

Uses & Applications

Phase diagrams are used in: materials science (alloy phase diagrams guide heat treatment, solidification control), chemical engineering (design of distillation, extraction, crystallisation), supercritical fluid technology (CO₂ phase diagram guides SFE design), geology (mineral stability under crustal conditions), and food science (chocolate tempering uses the cocoa butter phase diagram).

Safety Information

Phase diagrams identify conditions where dangerous phase transitions occur: the ice-water-steam system explains steam explosions; CO₂ solid-gas transition explains dry ice handling (sublimation produces large volumes of CO₂ gas in confined spaces — asphyxiation hazard). Process engineers must design for all phases that may occur under operating conditions.

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

Key Facts

Term Phase Diagram

Index All "P" terms

Synonyms Phase diagram, P-T diagram, state diagram, stability diagram

Frequently Asked Questions

What is Phase Diagram?

A graph showing the physical states of a substance as a function of temperature and pressure. It contains regions for solid, liquid, and gas phases separated by boundary lines. The triple point is where all three phases coexist; the critical point is where liquid and gas become indistinguishable.

What is Phase Diagram used for?

Is Phase Diagram hazardous?

More "P" Terms

P-type Semiconductor Pairing Pairing Energy Palladium Pd Parachor [P] = M(γ)^(1/4) / (ρ_L - ρ_V) Paramagnetic χ_m > 0; unpaired electrons; μ = √(n(n+2)) BM (n = unpaired electrons) Paramagnetism Partial Ionic Character % ionic = (1 - e^(-Δχ²/4)) × 100% Partial Pressure Partial Pressure p_i = x_i × P_total; P_total = Σp_i Particulate Matter Parts Per Million ppm = mg/L (water) or mg/kg; = (mass solute/mass solution) × 10⁶

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