When the products of a reaction are hotter than the reactants, an exothermic reaction is happening. An exothermic reaction is a reaction that releases energy to the surroundings. The energy released should be more than what is absorbed in order to maintain the reaction.
Iron is left in the filter and salt solution (salt and water) passes into the cup.
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He proposed the Law of Conservation of Matter, being the first to say that matter can not be created nor destroyed.
