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Lesson 1-5. What Are Chemical Reactions?. I. Changes in Matter A. Physical Changes 1. Changes where no new substances are formed 2. All changes are changes in state a. solid -> liquid b. liquid -> gas c. gas -> liquid
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Lesson 1-5 What Are Chemical Reactions?
I. Changes in Matter A. Physical Changes 1. Changes where no new substances are formed 2. All changes are changes in state a. solid -> liquid b. liquid -> gas c. gas -> liquid 3. Appearance changes (size, shape, or volume)
B. Chemical Changes (reactions) 1. One or more new substance is produced 2. Indicators of chemical reactions: a. light b. bubbles (gas) c. temp change (hot/cold) d. color change e. appearance of a solid
II. Chemical Reactions A. Substances change into other substances. B. Reactants = The substances used in a reaction. What you start out with. 1. Ex. Sodium + Chlorine C. Products = The substances you get out of a reaction. What you end up with. 1. Ex. Water + Sodium + Chlorine = Sodium Chloride & Energy (light & heat)
D. Types of Chemical Reactions 1) Compounds break apart 2) Elements combine to make a compound a) Long chains of molecules form (paper clips linked) E. Salts 1) Form when an acid and a base react a) Ex. Table Salt – NaCl Sodium & Chlorine
Law of Conservation of Matter A. New substances formed in chemical changes are not new matter 1. atoms are same, but in a different arrangement B. Law of Conservation of Matter states that matter is not created, nor is it destroyed 1. mass stays the same