A process in which two or more substances when mixed together produce one or more new substances.

Chemical Reaction

A + B → C

reactants product

When a chemical reaction occurs the products and reactants may have different properties

you can observe

Evidence of a Chemical Reaction

liquid + liquid → solid precipitate

liquid + solid → gas bubbles or fizz

Examples:

white + red → brown different color

cool + warm → hot change in temperature

It is likely a chemical reaction has occurred if you observe:

1. Gas formation2. Precipitate formation3. Change in color4. Change in temperature

WARNING!Physical changes are not chemical reactions

• Physical changes include: melting, freezing, boiling, evaporating,dissolving

• Physical changes are reversible Chemical changes are NOT reversible

• Physical changes do not produce new substances

Chemicals to mix: Observations: Is there evidence a new substance formed?

Is it likely that a chemical reaction took place?

One:calcium chloridebaking sodaWater

Two:Calcium chlorideCitric acidwater

Three:Citric acidBaking sodawater

Why is the Statue of Liberty green?

Homework