‘Hot ice’ is created using sodium acetate, which is a salt created from the reaction between sodium bicarbonate, or baking soda, and acetic acid, or vinegar. When this reaction occurs, sodium acetate appears to freeze like ‘ice’ as the cold solution turns from liquid to solid.
This process is exothermic, meaning that the solid structure is warm to the touch. Solutions of sodium acetate are used in certain types of hand-warmers. When a metal button is pressed inside the plastic pouch containing the solution, it releases chemicals that starts the reaction. Don’t worry his hand is fine.