Chemical Properties 0807.9.2 Identify the common outcome of all chemical changes. I can describe an example of a chemical change. I can explain what happens during a chemical change. I can differentiate between physical and chemical changes.

Chemical Properties Chemical Properties – describe matter based on its ability to change into new matter with different properties Flammability – the ability of a substance to burn Reactivity – the ability of two or more substances to combine and form one or more new substances. A chemical change alters the identity of a substance Chemical changes can not be easily undone

Comparing Physical and Chemical Properties How do you tell a physical property from a chemical property? You can observe physical properties without changing the identity of the substance such as changing it’s shape or state of matter. Chemical properties aren’t as easy to observe. They include reactivity with oxygen and flammability.

Characteristic Properties Characteristic properties are the most useful in identifying a substance. These properties remain the same no matter if the size of the sample changes. They include physical properties such as density and solubility and chemical properties such as flammability and reactivity. Scientist use these properties to classify substances.

Chemical Properties Used to Identify Matter pH – a measure of the acidity of a liquid Precipitate – a solid substance that separates from a liquid Corrosion – when metals change, often falling apart, due to chemical action Generation of a gas Change in color Absorption or release of heat

Chemical Change View - Evidence of a Happens when one or more substances are changed into new substances that have new and different properties. Changes the way the molecules link up Makes new substances View - Evidence of a physical reaction http://www.schooltube.com/video/39131/Gummy-Bear-Reaction

Here are some other examples of chemical changes: raw egg becomes cooked egg cake mix becomes cake

Matter and Chemical Changes Chemical changes change the identity of the matter involved. Most chemical changes are hard to reverse Some chemical changes can be reversed by more chemical changes Example: the water formed in the space shuttle’s rockets could be split into hydrogen and oxygen using an electric current

Physical versus Chemical Change The most important question to ask is: “Did the composition change?” Composition – the type of matter that makes up an object and the way that the matter is arranged in the object Physical changes do not change the composition of a substance, but chemical changes do. Electrolysis – a chemical change where water is broken down into hydrogen and oxygen gases

It’s a chemical change if…. It produces heat Sound or light are given off

It’s a chemical change if... It bubbles (makes a gas), fizzes or foams

It’s a chemical change if... It changes color or odor It forms a precipitate

What kind of change is it if someone... Tears up paper? Physical change Mixes salt and water?

What kind of change is it if someone... Burns paper? Chemical change Evaporates salt water? Physical change

What kind of change is it if someone... Mixes vinegar and baking soda? Chemical change

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