Try on your own and write answers on the board… Daily Opener Questions Try on your own and write answers on the board…

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Chemical Reactions Take Place… Every minute of every day both in and around you Examples: Digestion Photosynthesis Car batteries-to start your car Rust

Reactions: One or more substances, the ___________ change into one or more new substances, the __________. It is written as: Reactants → Products The arrow means “yields” or “reacts to produce” reactants products

Chemical Reactions A Balancing Act

Explanation: An explanation was proposed by _____________ who stated in his atomic theory that in a chemical reaction, the way in which atoms are joined together are changed. As reactants are converted to new products, __________that hold atoms together are __________ and new ones are formed. Dalton bonds broken

Law of Conservation of Mass Explanation: Daltons atomic theory explains the ____________________________. Which States: In any physical or chemical change mass is neither created nor destroyed. The atoms in the products are the same atoms that were in the reactants, they are just arranged differently. Law of Conservation of Mass

Explanation/Practice: In a word equation, reactants are written on the ___________ and products are written on the ________. Write the equation for… Copper can be produced by heating copper (II) sulfide with oxygen. Sulfur dioxide is also produced. Water is formed by the explosive reaction between hydrogen and oxygen left right

Answers Copper(II)sulfide + Oxygen → Copper + Sulfer dioxide Hydrogen + Oxygen → Water (Dihydrogen monoxide)

Meaning of Chemical Formula Symbol Meaning Composition H2O One molecule of water: Two H atoms and one O atom 2 H2O Two molecules of water: Four H atoms and two O atoms H2O2 One molecule of hydrogen peroxide: Two H atoms and two O atoms

Meaning of Chemical Formula When a __________ is written after the chemical symbol for an element it indicates the___________________. When a coefficient is written in front of an atom or molecule it indicates the ____________ of that atom or molecule that is present. If there are subscripts in that atom/molecule they need to be ____________ by the coefficient. subscript # of that element number multiplied

Reactants  Products Unbalanced Timberlake, Chemistry 7th Edition, page 164

Unbalanced and Balanced Equations H Cl Cl H H Cl H Cl Cl Cl H Cl H H H2 + Cl2  HCl (unbalanced) H2 + Cl2  2 HCl (balanced) reactants products reactants products H 2 1 H 2 2 Cl 2 1 Cl 2 2 Timberlake, Chemistry 7th Edition, page 167

How do we go from Unbalanced to Balanced Equations? You ____________ change the formula of your atom/ion/molecule! This means you may not change the ___________ ! Instead, you may put a coefficient __________ of your atom/ion/molecule to balance the number of atoms after you have ___________ it by the subscript MAY NOT subscript in front multiplied

CH4 + 2 O2  CO2 + 2 H2O Balanced! Reactants Products 1 C atom 1 C atom 4 H atoms 4 H atoms 4 O atoms 4 O atoms Balanced! Timberlake, Chemistry 7th Edition, page 167

Coefficient  subscript = # of atoms Balancing Steps 1. Write the unbalanced equation. 2. Count atoms on each side. 3. Add coefficients as needed to make #s equal on both sides of the equation. Coefficient  subscript = # of atoms 4. Reduce coefficients to lowest possible ratio, if necessary. 5. Double check atom balance!!!

Helpful Tips Balance one element at a time. Update ALL atom counts after adding a coefficient. If an element appears more than once per side, balance it last. Balance polyatomic ions as single units. “1 SO4” instead of “1 S” and “4 O”

Balancing Example 2 Al + CuCl2  Cu + AlCl3 Al Cu Cl 3 3 2 2  1 1 2 3 Aluminum and copper(II) chloride react to form copper and aluminum chloride. 2 Al + CuCl2  Cu + AlCl3 Al Cu Cl 3 3 2 2  1 1 2 3  2  6 3  6   3

More Examples… P + O2 → P4O10 H2 + O2 → H2O BaCl2 + H2SO4→ BaSO4 + HCl Cu + AgNO3 → Cu(NO3)2 + Ag CaCO3 + HCl → CaCl2 + H2CO3 5 2 2 2 2 2 2

When writing Chemical Rxns… It is important to indicate what “state” the atom/molecule is in (s): solid (l): liquid (g): gas (aq): aqueous solution – a solution in which the solvent is water ∆: heat