Unique and Dramatic Change-of-State Demonstrations In a Convenient Pack

• Eliminate the need for messy chemicals in change-of-state demonstrations with this portable, non-toxic heat pack
• 13 x 9 cm size

The pack contains a super-cooled and super-saturated solution made of food-grade sodium acetate and water. A stainless 1.7cm steel disk is is also enclosed. Flexing the disk activates two simultaneous chain reactions which induce rapid crystallization. Stored energy is released throughout the solution as it crystallizes. In about five seconds, the pack can reach a temperature of up to 40°C and will stay warm for about two hours. The pack is reusable, simply recharge it in boiling water for about six minutes.