Classification of Matter

Every sample of matter can be classified as a: Pure Substance Mixture Element Molecule Diatomic molecule Compound Homogeneous Solution Heterogeneous Colloid Suspension

Pure Substances Pure Substances cannot be broken down into any other substances by 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

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

Pure Substances   Compounds are either molecules or salts – need more on salts Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Sodium Chloride – NaCl (Table Salt) Sodium (Na) - Metal Chlorine (Cl) - gas Sodium Chloride NaCl   Fixed ratio: 1 Na for every 1 Cl Sodium in water video

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

Diatomic Elements, 1 and 7 H2 N2 O2 F2 Cl2 Br2 I2

Diatomic molecules are molecules composed only of two atoms, of the same elements. The prefix di- means two in Greek. Common diatomic molecules are hydrogen (H2), nitrogen (N2), oxygen (O2), Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).

Chemical Formulas Shows the compound and the ratio of atoms

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 Examples: rubbing alcohol (ethyl alcohol and water) Air (nitrogen and oxygen)

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

MATTER yes no MIXTURE PURE SUBSTANCE yes no yes no Homogeneous Mixture Can it be physically separated? MIXTURE PURE SUBSTANCE yes Is the composition uniform? no yes Can it be chemically decomposed? no Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element Colloids Suspensions Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Elements, Compounds, and Mixtures Consider Concentration Here! 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

Both elements and compounds have a definite makeup and definite properties. Mixtures two or more substances that are physically mixed Elements only one kind of atom; atoms are bonded if the element is diatomic or polyatomic Compounds two or more kinds of atoms that are chemically bonded substance with definite makeup and properties

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

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

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

Classification of Matter                                                                                                                                                        Matter Physically separable Substance Definite composition (homogeneous) Mixture of Substances Variable composition Basis for separation: different components, different properties. Strategy: devise a process that discriminates between components with different properties. high density / low density reactive / inert volatile / nonvolatile soluble / insoluble polar / nonpolar magnetic . nonmagnetic Chemically separable Element (Examples: iron, sulfur, carbon, hydrogen, oxygen, silver) Compound (Examples: water. iron (II) sulfide, methane, Aluminum silicate) Homogeneous mixture Uniform throughout, also called a solution (Examples: air, tap water, gold alloy) Heterogeneous mixture Nonuniform distinct phases (Examples: soup, concrete, granite)

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

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

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

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

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

Separating a Mixture

Separating a Mixture Chromatography - To separate different colored dyes. The dyes travel up the chromatography paper at different distances before they cannot remain in solution. The more soluble dyes move further up than the less soluble ones, hence separating from each other.

Separating a Mixture Distillation - to separate and collect a liquid from a solution of a soluble solid. The solution is heated in a flask until the liquid boils. The vapor produced passes into the condenser where it is cooled and condenses to a liquid. The pure liquid (distillate) is collected in a beaker.

Separating a Mixture Evaporation – This method is suitable to separate a soluble solid from a liquid. If the solution is heated, the liquid evaporates leaving the solid behind.

Separating a Mixture Fractional Distillation - This is a special type of distillation used to separate a mixture of liquids. Different liquids boil at different temperatures. When heated, they boil off and condense at different times. The apparatus features a fractionating column, which ensures that only the liquid boils at its boiling point will pass into the condenser.

Separating a Mixture Filtration – To separate an insoluble solid from a liquid. The solid remains in the filter paper and the liquid goes through the paper into the beaker.