Enthalpy

Transmutation cantrip

Casting Time: 1 action
Range: 30 feet
Components: S
Duration: Instantaneous
By waving your hand and pointing at a substance within range, you can make quick changes to the pressure, energy and temperature of it and its surroundings, changing its current state. You can turn up to 1 pint of liquid into a different state, such as water into ice or mercury into vapor.

Alternatively, you may change the substance's temperature so it's on the edge of changing states, such as making a cup of water instantly boiling hot or freezing cold.