Section 3.2—Properties of Matter

1. Section 3.2—Properties of Matter What properties are useful or not useful in an airbag? • Objectives • distinguish between chemical and physical • properties • distinguish between extensive and intensive • properties

2. Physical Properties • A physical property is a characteristic that can be observed without changing the chemical composition of a sample of matter. • Because substances have an unchanging composition, the physical properties of substances are constant from one sample to another. Some of them may be used to identify the substance. • Examples: color, shape, mass, odor, taste, hardness, density, state, solubility, melting point, boiling point.

3. Practice Problems • List the physical properties of the following:

4. Observing Physical Properties • PHYSICAL PROPERTIES • Appropriate observations would include: • White color • Small, crystalline particles • Particles are lustrous; long rectangular shape. • Inappropriate observations: • Looks like salt

5. Chemical Properties • A chemical property is a property of a substance that cannot be observed unless the substance has changed its chemical composition. • Chemical reactivity or the ability/inability of a substance to react with another substance is a chemical property. • Other chemical properties are the ability/inability to oxidize (combine with oxygen) & flammability (the ability to ignite).

6. Observing Chemical Properties CHEMICAL PROPERTIES • Appropriate observations include: • Combines readily with oxygen • Reacts vigorously with water • Inappropriate observations: • Rusts • Dissolves in water Calcium

7. Physical versus Chemical Properties Chemical Property Physical Property Can be observed or tested without changing the atoms or molecules In the process of observing or testing, the atoms or molecules are changed into a different substance

8. Let’s Practice Flammability Boiling point Solubility Malleability Reactivity with oxygen Example: Are the following properties are physical or chemical?

9. Let’s Practice Flammability Boiling point Solubility Malleability Reactivity with oxygen Chemical Physical Physical Physical Chemical Example: Are the following properties are physical or chemical?

10. Intensive and Extensive Properties Intensive Property Extensive Property Size of the sample doesn’t matter—you’d say a big piece and a small piece were the same with respect to this property Size of the sample does matter—a big piece and a small piece would be different with respect to this property

11. Let’s Practice Mass Volume Color Flammability Texture Example: Are the following properties are intensive or extensive?

12. Let’s Practice Mass Volume Color Flammability Texture Extensive Extensive Intensive Intensive Intensive Example: Are the following properties are intensive or extensive?