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Chapter 4, section 1 Chemical Changes I will describe the signs of a chemical change in matter. Agree 1._______ Disagree All chemical changes result in a new ________ substance being formed. All chemical reactions produce heat. 2._______ ________ 3._______ A chemical reaction caused the Statue of ________ Liberty to become green. 4._______ A change in smell is usually a sign of a ________ physical change 5._______ ________ Some chemical reactions can create light. I. Chemical Change A. Occurs when bonds in compounds break and new compounds form 1. In a physical change, compounds remain the same Metal elements bonding with oxygen II. Evidence A. chemical reactions will always have: - formation of a new substance - a change in energy http://www.youtube.com/watch?v=66kuhJkQCVM B. Visual Evidence: 1. Precipitate – when two liquids react and form a solid substance 2. Color change 3. Gas produced 4. Change in odor (smell) http://www.youtube.com/watch?v=DITY2rXYU-I Tons and Tons of Precipitation Reactions! http://www.youtube.com/watch?v=JAeOP2MfrDY&list=TLJvZzUIA5KeR y6b7rNi2dHxKjeqYsLjFE C. Energy Evidence 1. Temperature decrease = endothermic 2. Temperature increase = exothermic http://www.youtube.com/watch?v=Jzoi7dJAiSc&feature=related Let’s Review Chemical Changes! http://www.youtube.com/watch?v=cZMkqagL8Ps Agree 1._______ Disagree All chemical changes result in a new ________ substance being formed. All chemical reactions produce heat. 2._______ ________ 3._______ A chemical reaction caused the Statue of ________ Liberty to become green. 4._______ A change in smell is usually a sign of a ________ physical change 5._______ ________ Some chemical reactions can create light. Please pull out your science book to pg 660 and start reading