Physical & Chemical Changes

Only alter the form or appearance of matter Physical Changes Only alter the form or appearance of matter A substance that undergoes a physical change is still the same substance after the change Cutting paper, coloring a picture, building a snowman, breaking glass, making an origami Yoda, sharpening pencils & melting butter are all examples of physical changes.

How can you tell? There are some indicators that will let you know when a physical change has taken place: Phase change You just physically mixed things together (like Kool-Aid or a salad) The only thing that changes is the shape or size There is an expected color change A lot of times the change can be reversed

A physical change is similar to changing the font of a word… Physical Changes A physical change is similar to changing the font of a word… Basketball The structure of the word is still the same, but the physical appearance has changed.

Quick Check 1) You are given a piece of paper. What are 2 things that you could do to the paper that would result in a physical change? 2) When something changes state, like melting ice for example, why is it considered a physical change? Tear it, crumple it, fold it, cut it, color it, write your name on it, etc. Nothing new is formed – frozen or melted, water is still H2O (its structure has not changed)

Produce one or more new substances Chemical Changes Produce one or more new substances Grilling food, spoiling/rotting food, oxidation, fireworks, rusting, and a burning candle are all examples of a chemical change.

How can you tell? There are some indicators that will let you know when a chemical change has taken place: Anytime something is cooked and/or burned Light, sound, and/or heat is produced A gas is produced (or you see fizzing or bubbling) A precipitate forms There is an unexpected color change

Chemical Changes A chemical change is like rearranging the letters of a word… Basketball Let Blab Ask Lab Bat Elks Ask Bell Tab Stab Elk Lab Bask At Bell The structure has been rearranged and new words were made.

Chemical Changes Chemical changes can be endothermic (absorb energy) or they can be exothermic (release energy). The prefix “endo” means enter. An example of an endothermic reaction is an ice pack. The prefix “exo” means exit. An example of an exothermic reaction is an explosion.

As you watch the following video… Look for any indications that a chemical change is taking place. https://www.youtube.com/watch?v=hKoB0MHVBvM A gas (carbon dioxide) was produced