Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Unit 1A ACS Chemistry in the Community Sixth Edition

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Chemical Symbols and Formulas UNIT 1.A.6 AND 7

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Mixtures, elements, compounds  Scientists like to classify things.  One way that scientists classify matter is by its composition.  Ultimately, all matter can be classified as mixtures, elements and compounds.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers By asking these questions scientists can classify matter into:  Mixtures – two or more substances that are not chemically combined with each other and can be separated by physical means. The substances in a mixture retain their individual properties.  Solutions – a special kind of mixture where one substance dissolves in another.  Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means.  Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Elements  Elements are the simplest pure substance.  An element can not be changed into a simpler substance by heating or any chemical process.  The smallest particle of an element that has the properties of that element is called an atom.  An atom is the basic building block of matter.  There are more than one hundred known elements in the universe listed on the periodic table of elements.  These elements combine in such a way to create millions of compounds.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Elements  All elements are made of atoms.  Atoms of the same element are alike.  Atoms of different elements are different.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Elements  In 1813, a system of representing elements with symbols was introduced.  Each symbol consists of one or two letters.  Two letters are needed for a chemical symbol when the first letter of that element’s name has already been used.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Common Elements AluminumAl BromineBr CalciumCa CarbonC GoldAu HeliumHe HydrogenH NitrogenN

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Chemical Symbols  All elements in the Periodic Table have symbols that are recognized world wide.  It does not matter which country you are in or the language you speak.  Example: The element Iron is always identified by “Fe” and Oxygen is “O”.  The names are not always the same but the symbols are. “Fe” is iron in Canada, fer in France and fier in Romania.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Chemical Symbols A Chemical symbol is an abbreviation of a name of an element. Capital letter if only one letter. Only first letter capital if more than one letter Element Chemical Symbol OxygenO NitrogenN HydrogenH SodiumNa

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Sodium comes from the word sodanum, a headache remedy, and it’s symbol (Na) comes from the Latin word Natrium.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers

Compounds  Compounds are also pure substances.  But compounds are made from more than one element.  Water is a compound.  Water can be broken down into simpler substances – hydrogen and oxygen.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers

Chemical Formulas A chemical formula is the combination of symbols that represent a particular compound. The chemical formula indicates which elements are present in the compound and in what proportions. Ex. 1: Water molecule H 2 O: 2 atoms of hydrogen, 1 atom of oxygen Ex. 2: Iron Oxide molecule Fe 2 O 3 : 2 atoms of iron, 3 atom of oxygen

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Chemical Formulas - Examples  Calcium Carbonate (chalk) – CaCO 3  Sodium Chloride (salt) – NaCl  Acetysalicylic acid (aspirin) – C 9 H 4 O 8  Acetic acid (vinegar) – C 2 H 4 O 2 

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Chemical Formulas  NOTES: - Each symbol in a formula represents an element. - If only one atom of an element is present in the compound, no subscript is used. - If more than one atom of an element is used, then the symbol is followed by a number indicating how many atoms are used. This is called the subscript.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers

I. CHEMICAL EQUATIONS A. Definitions 1. Chemical Equation - represents reactants and products in a reaction using symbols, formulas and coefficients. 2. Subscript - indicate the number of atoms of an element in a chemical reaction. 3. Coefficient - whole number in front of a formula or symbol that indicates the number of atoms, molecules, formula units or moles

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Subscripts vs. Coefficients  The subscripts tell you how many atoms of a particular element are in a compound. The coefficient tells you about the quantity, or number, of molecules of the compound.

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers

CHEMICAL REACTIONS Reactants: Zn + I 2 Product: Zn I 2

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Chemical Reactions

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers B. Methods for Writing Equations 1. word equation – reactants and products are represented by words 2. formula equation- reactants and products are represented by element symbols and formulas 3. balanced chemical equation – a formula equation using coefficients to represent the number of atoms, molecules, or formula units

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers C. Symbols Used in Writing Equations > yields, forms, produces, reacts to form > reversible reaction (products < react to re-form the reactants) 3. symbols or words written above -----> a. triangle – reaction requires heat b. o C – indicates temperature required c. atm – indicate pressure is required d. symbol for element or formula for compound – catalyst is required

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers 4. letters or symbols next to formula a. letters (s) – solid (l) – liquid (g) – gas (aq) – aqueous solution b. symbols arrow point up – gas produced arrow pointing down–precipitate forms

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Chemical Equations 4 Al(s) + 3 O 2 (g) --- > 2 Al 2 O 3 (s) This equation means 4 Al atoms + 3 O 2 molecules ---produces---> 2 molecules of Al 2 O 3 2 molecules of Al 2 O 3 AND/OR AND/OR 4 moles of Al + 3 moles of O 2 ---produces---> 2 moles of Al 2 O 3 2 moles of Al 2 O 3

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers   1. Define the terms “reactants” and “products.” Give examples of each from a chemical equation.  2. What do all chemical reactions need?  3. What do you think E A stand for?  4. What role does a catalyst play in a chemical reaction?

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers

II. CHEMICAL REACTIONS A. Bonds and Chemical Reactions 1. bonds form, break or both 2. atoms combine, separate, rearrange A + B  A-B C-D  C + D A-B + C  C-B + A C-D + B  C-B + D A-B + C-D  A-D + C-B

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers ductile Not ductile

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers Watch periodic tables: