Chemical Properties Property of matter that describes a substances ability to participate in chemical reactions. (Change into new matter.) Flammability ability to burn Burning wood creates ash and smoke Reactivity ability of two or more substances to combine and form a new substance Oxygen and iron create rust

Physical and Chemical Properties Comparing Physical and Chemical Properties Physical properties may be observed without changing the identity of the substance. Density, Hardness, Color Chemical properties can not be observed until the chemical reaction takes place. A piece of wood is flammable even when it is not burning, but must be burning to observe this property

Characteristic Properties Properties most useful in identifying a substance. Always the same no matter the size of the sample Physical properties Density, Hardness Chemical Properties Flammability, reactivity Used to identify and classify substances

Chemical Change When two or more substances are changed into an new substance Learn about chemical properties through chemical changes Examples: Digestions Burning wood Rust Soured milk

Signs of a Chemical Change What Happens During A Chemical Change Ingredients combine to form a new substance Baking a cake Change in color, odor Production of heat, sound, light Change the identity of the matter involved This makes them very hard to reverse Some chemical changes can be reversed Water split back into oxygen and hydrogen using electric current Signs of a Chemical Change Matter & Chemical Changes

Physical vs. Chemical Change Did the composition change? Composition is the type of matter that makes up an object and the way that matter is arranged Chemical changes alter the composition of the substance. Many physical changes may be easily reversed Melted ice cube can be frozen again Chemical Changes are not easily reversed Water separated into hydrogen and oxygen Reversing Changes