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Endothermic reaction between barium hydroxide and ammonium chloride. A beaker containing the two chemicals is set on a block of wood dampened with water. As the chemicals are mixed, there is a dramatic drop in temperature. Here, near the end of the mixing, the chemicals have formed a slush and the temperature has dropped to -16C. This freezes the water beneath the beaker so that the block of wood sticks to it.
Model release not required. Property release not required.