Understanding Chemical and Physical Reactions
About the Understanding Chemical and Physical Reactions Lesson
A lesson on physical and chemical reactions.
• To introduce students to the two types of reactions.
• To teach the signs of a physical change.
• To teach the signs of a chemical change.
• To explain the differences between a physical and chemical reaction.
• To present exercises that test students? understanding of chemical and physical reactions and how they differ.
• To present exercises that test student?s ability to identify physical and chemical changes.
The first way matter can change is through a physical reaction. A physical reaction causes the matter to shift shape or state. For example, if you crush a cardboard box, only the shape changes. It has the same molecules, and is still a cardboard box, even if it is flat. This is a physical reaction. Another kind of physical reaction is an ice cube melting. As it melts, the ice changes from a solid to a liquid state. Even though it is no longer frozen, the matter is still water. That makes it a physical change.