Matter: Properties & Changes Glencoe: Sections 3.1 and 3.2

3.1 Properties of Matter A substance has a fixed composition and differs from a mixture in the following ways: 1. every sample of a given substance has exactly the same characteristic properties. 2. every sample of a given substance has exactly the same composition.

Pure substances are either compounds or elements. A compound can be decomposed into simpler compounds or elements by a chemical change. For example, water can be broken down into its component elements by electrolysis.

Physical Property A physical property can be observed or measured without changing the material’s composition. Most physical properties you can see. But some you cannot. An extensive physical property is a property that is dependent on the amount of substance. Length and volume are extensive. Intensive physical properties are independent of amount of substance. Density is intensive.

Chemical Property A chemical property is something that isn’t obvious. It is the ability of a material to combine with or change into one or more other substances as a result of contact with either thermal or electrical energy. Example: ability to rust, flammability.

3.2 Changes in Matter A change that alters a substance without altering its composition is a physical change. Chemical changes are those where substances change into new substances. Another name for a chemical change is a chemical reaction.

States of Matter All matter can be classified into three types: solid, liquid and gas. Solids have a definite shape and volume, and therefore cannot be compressed. Solids are NOT defined by rigidity or hardness.

Liquids flow, have a constant volume, but not a definite shape. Liquids take the shape of their containers. Liquids cannot be compressed. Gases also flow and take the shape and volume of their containers. Gases can be compressed.

Law of Conservation of Mass Mass is neither created nor destroyed; it is conserved. Therefore, in any chemical reaction, the amount of the reactants must equal the amount of the products. Mass reactants = Mass products

Example: If you have 216 g of mercury (II) oxide and it decomposes into mercury and oxygen, then the elements combined must have the same mass as the mercury (II) oxide.

Review: What is a substance? Name three physical properties. Name three chemical properties. What is a physical change? Give an example? List four indicators of a chemical change. Solve: A 10 g sample of potassium chloride decomposes into 6.4 g of potassium. How much chlorine was in the sample?