Matter & Change Chapter 2

2.1: Properties of Matter A substance is matter that has a uniform and unchanging composition. (pure substance) A physical property is a characteristic that can be observed or measured without changing the composition of the sample.

2.1 Cont. 2 types of Physical Properties Extensive Properties depend on the amount of a substance. Intensive Properties are independent of the amount of a substance. A chemical property is the ability or inability of a substance to combine with or change into one or more other substances

2.1 Cont. States of Matter Solid Liquid Gas Plasma Definite shape & volume Incompressible Relatively slow moving particles Tightly packed particles

2.1 Cont. Liquid Gas (Vapor) Constant volume Takes the shape of the container, flows Less closely packed particles Particles move more quickly Virtually incompressible Gas (Vapor) Takes the shape of the container Fills the container Particles move rapidly Particles far apart Easily compressible

2.1 Cont. Types of Changes Physical Chemical A physical change is a change that alters a substance w/o changing its composition. Reversible & Irreversible A chemical change is a process that involves 1 or more substances changing into new substances. (Chemical Reaction)

2.2: Mixtures Mixture A combination of 2 or more pure substances in which each pure substance retains its individual chemical properties. Types of Mixtures Heterogeneous Doesn’t blend smoothly throughout; individual substances remain visually distinct Homogeneous Constant composition throughout; always a single phase solution

2.2 Cont. Separating Mixtures Filtration Distillation Crystallization Chromatography

Filtration

Distillation

Chromatography

2.3: Elements & Compounds Substances can be classified as elements & compounds. An element is a pure substance that can’t be broken down into simpler substances by chemical or physical means. 91 elements naturally occurring on earth About 120 known elements

2.3 Cont. A compound is two or more different elements combined chemically. Approximately 10 million known compounds Approximately 100,000 new compounds discovered every year. Compounds can be broken into simpler substances by chemical means. The properties of a compound are different than those of the individual elements

2.4: Chemical Reactions Reactants Products Clues a Reaction has Taken Place Law of Conservation of Mass Mass is neither created nor destroyed during a chemical rxn – it is conserved. Mass reactants = Mass products