At what temperatures does water change state?

At 1 atm, water freezes/melts at 0 °C (32 °F) and boils/condenses at 100 °C (212 °F). These points shift with conditions: lower pressure (high altitude) lowers the boiling point; higher pressure (pressure cooker) raises it, and ice’s melting point drops slightly under pressure.

 Solutes (e.g., salt) cause freezing-point depression (sea water ≈ −2 °C) and boiling-point elevation (small increase). Key landmarks: triple point at 0.01 °C, 611 Pa (solid–liquid–gas coexist), and critical point at 374 °C, 22.06 MPa (no distinct liquid/gas). 

Non-ideal behaviors include supercooling (liquid below 0 °C) and superheating (liquid above 100 °C in very smooth containers). Phase changes can also bypass the liquid: sublimation (ice → vapour) and deposition (vapour → ice), common in very dry or low-pressure air.