Chemical properties describe how a substance reacts or changes during a chemical reaction. Some key chemical properties include flammability, reactivity, and the ability to change composition. There are several clues that indicate a chemical change rather than a physical change has occurred, such as a change in color, production of a gas, or formation of a precipitate. However, not all instances of these clues necessarily mean a chemical reaction took place, and the definitive test is whether the composition of the matter changes to produce different substances.

1. Chemical Properties

2. Goals: To describe chemical properties of matter. To learn the clues that indicate that a chemical change has taken place. To distinguish between chemical and physical changes.

3. Access Prior Knowledge: What caused the car in the first slide to rust?

4. What is a chemical property? The ability to produce a change in the composition of matter. They can be observed only when one substance in a sample of matter is changed into another substance. Ex.-whenever something is burned, that substance becomes something completely different. The ability to burn is a chemical property.

5. Flammability The ability to burn in the presence of oxygen.

6. Reactivity How easily a substance combines chemically with another substance. Oxygen easily reacts with many other elements. What other element is oxygen reacting with in this photo?

7. How Can You Recognize Chemical Changes? A change in color – Ex. The green patina on an old copper roof. Production of a Gas – Ex. Using baking powder and water in a cake mix. CO 2 is produced which helps the cake rise. Formation of a Precipitate – (any solid that forms and separates from a liquid). Ex. Adding vinegar to milk causes the proteins to clump together.

9. Can you think of physical changes that exhibit these clues also?

10. Is a change in color always an indicator of a chemical change?

11. Is the formation of a gas always an indicator of a chemical change?

12. Physical v. Chemical Changes Before you decide whether a chemical change has actually taken place, ask yourself this question: Are different substances present after the change takes place? If not, it is a physical change (the composition of the matter stays the same).