2.4 Chemical Changes Chemical Property ability to undergo a chemical change; “reactivity”; “behavior” observed when matter changes its composition can be used to identify matter e.g., burn, rot, rust, decompose, ferment, explode, corrode, oxidize, etc… 1
2.4 Chemical Changes Chemical Change change in the composition of matter a.k.a. chemical reaction REACTANT(S) PRODUCT(S) starting material finishing material; “new” substance 2
Recognizing Chemical Changes Possible “clues” to a chemical change: Transfer of energy (i.e. light &/or heat given off) Change in color Production of gas Formation of precipitate (a solid that forms out of a liquid) Clues do not necessarily confirm chemical change. 3
Conservation of Mass The Law of Conservation of Mass Mass is neither created nor destroyed in any chemical reaction. Mass of reactants = mass of products 4
Conservation of Mass 5
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Conservation of Mass 7