Class Opener: Tuesday, September 10 Distinguish between a physical change and a chemical change. Is the burning of gasoline is considered a physical or chemical change? the evaporation of gasoline? Explain reasoning of each of your choices.

Changes in Matter Physical Change – change that does not alter the identity of the substance. Changes in appearance only. All state changes are physical changes. Ex: tearing paper and ice cube melting Chemical Change – Change in which one or more substances are converted into new materials with different properties. (chemical reaction) Ex: burning paper and iron rusting

Its Your Turn! Determine if each of the following represents a chemical change or a physical change. Grinding chalk into a powder Digesting food Paper towel absorbs water Evaporation of alcohol Piece of jewelry turns skin green Sublimation of dry ice Making hydrogen gas from water Frying a hamburger

Signs of a Chemical Reaction How can we tell if a chemical reaction has occurred? Production of a Gas Color Change (usually) Evolution of Energy (heat and/or light) Formation of a precipitate precipitate – A solid that forms when mixing two liquid solutions

Energy and Changes in Matter Whenever a physical or chemical change occurs energy is always involved. Exothermic – Process in which energy is released. Ex: Burning paper Endothermic – Process in which energy is absorbed. Ex: Melting of an ice cube

One Minute Paper You have one minute to answer these two questions concerning today’s lesson. What was the most important thing you learned? What is still muddy? 6