Sequence of shots showing an endothermic reaction. At left solid barium hydroxide and solid ammonium chloride have been place in a flask that is sitti


Sequence of shots showing an endothermic reaction. At left solid barium hydroxide and solid ammonium chloride have been place in a flask that is sitting on a damp piece of wood. The digital thermometer shows the temperature in the flask to be 21 degrees Celsius. As the two chemicals are mixed an endothermic, or heat-absorbing, reaction takes place and the temperature inside the beaker drops dramatically. This drop in temperature freezes the water between the flask and wooden block, sticking the two together (right).


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Photo credit: © Science Photo Library / Alamy / Afripics
License: Licensed
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