Chapter 2Atoms and Elements 2.1 Classification of Matter Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

A pure substance is classified as  Matter with a specific composition.  An element when composed of one type of atom.  A compound when composed of two or more elements chemically combined in a definite ratio. Pure Substances

Elements Elements are  Pure substances that contain atoms of only one type. Copper Cu Lead Pb Aluminum Al Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Compounds  Contain two or more elements bonded together in a definite ratio. Salt (NaCl) Table sugar (C 12 H 22 O 11 ) Water (H 2 O) Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Elements in a Compound “Table salt” is a compound that contains the elements sodium and chlorine. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Reaction

Identify each of the following as a pure substance or a mixture. A. pasta and tomato sauce B. aluminum foil C. helium D. air Learning Check

Identify each of the following as a pure substance or a mixture. A. pasta and tomato saucemixture B. aluminum foilpure substance C. helium pure substance D. air mixture Solution

Mixtures A mixture is matter that consists of  Two or more substances that are physically mixed, not chemically combined.  Two or more substances in different proportions.  Substances that can be separated by physical methods.

Homogeneous Mixtures In a homogeneous mixture,  The composition is uniform throughout.  The different parts of the mixture are not visible. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Heterogeneous Mixtures In a heterogeneous mixture,  The composition is not uniform, it varies from one part of the mixture to another.  The different parts of the mixture are visible. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Identify each of the following as a homogeneous or heterogeneous mixture: A. hot fudge sundae B. shampoo C. sugar water D. peach pie Learning Check

Identify each of the following as a homogeneous or heterogeneous mixture: A. hot fudge sundaeheterogeneous mixture B. shampoo homogeneous mixture C. sugar water homogeneous mixture D. peach pie heterogeneous mixture Solution

Physical Separation of A Mixture The physical separation of a mixture  Involves only physical changes.  Occurs when is pasta and water are separated with a strainer. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings