Classification of Matter Elements, Compounds, and Mixtures

Pure Substances Pure Substance that cannot be broken down into any other substances by chemical or physical means Gold - element Manganese Dioxide - compound

Pure Substance Element composed of identical atoms EX: copper wire, aluminum foil http://www.friedlandindustries.com/images/new/NonferrousMetalsCopper.jpg Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Pure Substances Compound composed of 2 or more elements in a fixed ratio properties differ from those of individual elements Chemical bonds hold the elements together EX: table salt (NaCl) Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Pure Substances - FYI Law of Definite Composition A given compound always contains the same, fixed ratio of elements. Two different compounds, each has a definite composition Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Molecules Groups of two or more atoms bound by chemical bonds Can be two of the same element

Classification of Matter Ordinary solid salt is a compound but not a molecule. It is built from interpenetrating lattices of sodium and chloride ions that extend indefinitely. This well-known molecule is a compound because it contains more than one element. http://www.chem1.com/acad/webtext/pre/chemsci.html A molecule but not a compound Ozone, O3, is not a compound because it contains only a single element.

Chemical Formula-Extra Info Shows the compound and the ratio of atoms

Diatomic Elements, 1 and 7 H2 N2 O2 F2 Cl2 Br2 F2

Matter Flowchart Examples: graphite pepper element sugar (sucrose) paint soda element hetero. mixture compound hetero. mixture Graphite image: geology.about.com/.../bl/images/blgraphite.htm solution homo. mixture Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Classification of Matter hetero- geneous mixture no uniform properties? no solution fixed composition? http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld003.htm no element chemically decomposable? yes compound http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld003.htm

Elements Compounds Mixtures Both elements and compounds have a definite makeup and definite properties. Elements only one kind of atom; atoms are bonded it the element is diatomic or polyatomic Compounds two or more kinds of atoms that are bonded Mixtures two or more substances that are physically mixed substance with definite makeup and properties two or more kinds of and Packard, Jacobs, Marshall, Chemistry Pearson AGS Globe, page (Figure 2.4.1)

Mixtures Variable combination of two or more pure substances. Each keep individual properties Heterogeneous – Can see different parts (different) Homogeneous- Evenly Mixed cannot see different parts. (Same) Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Tyndall Effect The scattering of light by particles in a mixture http://www.youtube.com/watch?v=gheuYqQ6phE&feature=related

Mixtures Solution homogeneous very small particles no Tyndall effect particles don’t settle EX: rubbing alcohol (ethyl alcohol and water) Air (nitrogen and oxygen) Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Mixtures Colloid heterogeneous medium-sized particles Tyndall effect particles don’t settle Particles scatter light EX: Milk Clouds Smoke mayo Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Mixtures Suspension heterogeneous large particles Tyndall effect particles settle EX: fresh-squeezed lemonade Sand in water Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Mixtures Examples: colloid suspension colloid solution suspension mayonnaise muddy water fog saltwater Italian salad dressing colloid suspension colloid solution suspension Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Elements, Compounds, and Mixtures oxygen atoms hydrogen atoms hydrogen atoms “Elements, Compounds, and Mixtures”   Description: This slide shows the molecular composition of an element, a compound, and two mixtures. Basic Concepts All samples of a substance have the same molecular composition and intensive properties and are homogeneous. Elements and compounds are substances; mixtures are not. The elements making up a compound combine in fixed ratios. Mixtures can be separated by physical methods. Mixtures that have a uniform composition throughout are homogeneous; those that have parts with different compositions are heterogeneous. Teaching Suggestions Use this transparency to help students visualize the molecular composition of elements, compounds, and mixtures and to review the definitions of these terms. Make sure students understand the difference between the terms matter and substance. Remind students that elements and compounds are always homogeneous, while mixtures can be either homogeneous or heterogeneous. Questions: Which of the bottles pictured above contain(s) matter? Which contain(s) a single substance? Explain your answers. How many elements are present in each molecule of water shown in bottle (b)? What is the relative number of atoms of each element in a water molecule? As you know, ice is frozen water. In other words, ice and water are the same substance, in different phases. What would you expect the ratio of hydrogen atoms to oxygen atoms to be in a molecule of ice? Explain your reasoning. Bottle (c) and bottle (d) both contain mixtures. How are these mixtures similar? How are they different? Suppose you find an unlabeled bottle containing a clear liquid. Can you tell by looking at it whether the material is a compound or a mixture? Explain your answer. How can you prove that a sample of sea water is a mixture? Classify the following items as elements, compounds or mixtures; rice pudding, copper, carbon dioxide, air, milk, magnesium chloride, granite, mercury, and maple syrup. A chocolate-chip cookie with more chips in one part of the cookie than another can be used to demonstrate a heterogeneous mixture. Name two other materials that can be classified as heterogeneous mixtures. Explain your reasoning. (a) an element (hydrogen) (b) a compound (water) (c) a mixture (hydrogen and oxygen) (d) a mixture (hydrogen and oxygen) Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 68

Classification of Matter (gas. Liquid, solid, plasma) Separated by PURE SUBSTANCES MIXTURES physical means into Separated by COMPOUNDS ELEMENTS HOMOGENEOUS MIXTURES HETEROGENEOUS MIXTURE chemical means into Kotz & Treichel, Chemistry & Chemical Reactivity, 3rd Edition , 1996, page 31

Mixture vs. Compound Different Alike Different Topic Topic Mixture Involve substances Variable Composition Fixed Composition Topic Topic No bonds between components Contain two or more elements Bonds between components Mixture Compound Compounds have different properties than the elements they are made from. In a mixture, the mixture retains the properties of the materials it is made from. A chemical formula can always be written for a compound. Can be separated by physical means Can be separated into elements Can ONLY be separated by chemical means

Compounds vs. Mixtures Compounds have properties that are uniquely different from the elements from which they are made. A formula can always be written for a compound e.g. NaCl  Na + Cl2 Mixtures retain their individual properties. e.g. Salt water is salty and wet

Top Ten Elements in the Universe Percent Element (by atoms) Hydrogen 73.9 Helium 24.0 Oxygen 1.1 Carbon 0.46 Neon 0.13 Iron 0.11 Nitrogen 0.097 Silicon 0.065 Magnesium 0.058 Sulfur 0.044 A typical spiral galaxy (Milky Way is a spiral galaxy) Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 26

The Composition of Air Air Nitrogen Helium Oxygen Neon Water vapor Carbon dioxide Argon Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 34

Chart Examining Some Components of Air Nitrogen consists of molecules consisting of two atoms of nitrogen: Oxygen consists of molecules consisting of two atoms of oxygen: Water consists of molecules consisting of two hydrogen atoms and one oxygen atom: Argon consists of individual argon atoms: Carbon dioxide consists of molecules consisting of two oxygen atoms and one carbon atom: Neon consists of individual neon atoms: Helium consists of individual helium atoms: N2 O2 H2O Ar CO2 Ne He Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 35

Reviewing Concepts Classifying Matter Why does every sample of a given substance have the same properties? Explain why the composition of an element is fixed. Describe the composition of a compound. Why can the properties of a mixture vary? On what basis can mixtures be classified as solutions, suspensions, or colloids? Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 44 Every sample of a given substance has the same properties because a substance has a fixed, uniform composition. An element has a fixed composition because it contains only one type of atom. A compound always contains two or more elements joined in a fixed proportion. The properties of a mixture can vary because the composition of a mixture is not fixed. Based on the size of its largest particles, a mixture can be classified as a solution, a suspension, or a colloid. http://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Syndiotactic_polypropene.png/300px-Syndiotactic_polypropene.png