暖暖包沒插電，為什麼會發熱？鐵粉生鏽的放熱反應 Why Does a Hand Warmer Get Hot? Rusting Iron and Exothermic Reactions
暖暖包不是靠摩擦，也沒有電池。拆開外袋後，鐵粉和氧氣反應生鏽，放出熱，這是放熱反應，ΔH < 0。A hand warmer has no battery and does not run on friction. Once the bag is open, iron reacts with oxygen and rusts, giving off heat. That is an exothermic reaction, ΔH < 0.
