Chapter 4, section 1 Chemical Changes I will describe the signs of a chemical change in matter.

Agree Disagree 1._______ ________ 2._______ ________ 3._______ ________ 5._______ ________ 4._______ ________ All chemical changes result in a new substance being formed. All chemical reactions produce heat. A chemical reaction caused the Statue of Liberty to become green. A change in smell is usually a sign of a physical change 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

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)

y6b7rNi2dHxKjeqYsLjFE Tons and Tons of Precipitation Reactions!

C. Energy Evidence 1. Temperature decrease = endothermic 2. Temperature increase = exothermic

Let’s Review Chemical Changes!

Agree Disagree 1._______ ________ 2._______ ________ 3._______ ________ 5._______ ________ 4._______ ________ All chemical changes result in a new substance being formed. All chemical reactions produce heat. A chemical reaction caused the Statue of Liberty to become green. A change in smell is usually a sign of a physical change Some chemical reactions can create light.

Please pull out your science book to pg 660 and start reading