When she placed her hand on the side of the container, it felt really cold, but it didn't feel that way before. The temperature had dropped by about 30 degrees Celsius. The substance was now grey and crystallin in structure. Was this a chemical reaction? Answer the question (in a complete sentence) Provide evidence to support your claim and describe (reasoning/justify) how the evidence supports the claim.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.