Sodium acetate heat pad reacting (1 of 5). Sodium acetate is solid at 130 degrees F, but will exist as a liquid at a much lower temperature and is extremely stable. Clicking the metal disk forces a few molecules to flip to the solid state, and the rest of the liquid then rushes to solidify as well. The temperature of the solidifying liquid jumps up to 130 degrees F in the process. Boiling the pad melts the sodium acetate back to a liquid state, preparing the pad for future use.