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Chemical Reactions And Balancing Chemical Equations Vocabulary Terms Compound A molecule that contains at least two different atoms in an exact proportion. The atoms in this compound This compound has a are being held together by set proportion of the energy and forces created TWO to ONE by sharing electrons between the atoms. Chemical Changes Changing the makeup of a substance. Something is created! Signs ofNEW a Chemical Change: Heat Sound Smell Light Examples of things made by chemical reactions: Chemical Changes Matter is Never created or destroyed A chemical change takes “old” atoms and Rearranges them into something New. Reactant Reactant #1 #2 PRODUCT(s) TYPES of Chemical Changes Combustion Reaction is a type of chemical change in which a substance reacts with OXYGEN to produce energy. When things burn, new things are made. Heat Ash Light (1) Fuel This type of reaction requires THREE things (2) Oxygen (3) Spark TYPES of Chemical Changes Synthesis Reaction is a type of chemical change in which two or more substances combine to form a new substance Na Sodium Metal Cl Na Cl Sodium Chloride (NaCl) Chlorine Gas Sodium is a soft metal NaCl = regular ordinary, This that when placed in everyday……. water will actually…… EXPLODE! is a Poisonous gas. TYPES of Chemical Changes Double Replacement is a type of chemical change in which the positive ion from one compound switches places with the positive ion from another compound to form TWO new substances NaCl + KBr NaBr + KCl Chemical Changes Celebrity Double Replacements happen all the time Double (Even when there is no “CHEMISTRY”) Replacement Chemical Equations The way that scientist represent and explain a chemical reaction using the elements’ symbols Think of chemical equations like simple math addition problems! In math, you learned that both sides of the equation have to be equal. 5 = 10 + 5 10 = 10 H H H Hydrogen Gas H H O O Hydrogen Gas Oxygen Gas Chemical Equation: 2H2 + O2 2H2O H O H H O Water (H2O) Chemical Equations EXAMPLE Chemical Equation: 2H2 + O2 How many H’s are on the LEFT side? 4 How many O’s are on the LEFT side? 2 = 2H2O How many H’s are on the RIGHT side? 4 How many O’s are on the RIGHT side? 2 Balancing Chemical Equations By making both sides of a chemical equation equal, it tells scientist what amount of REACTANTS are necessary to make a certain amount of the PRODUCTS. Balancing chemical equations requires you to follow rules and understand how to write an atom’s symbol Every atom symbol is like your name… It begins with a capital letter C Carbon or Cl Chlorine Balancing Chemical Equations Follow these rules (1) After looking at the equation, Write down the number of atoms of each element on each side of the equation. EXAMPLE Chemical Equation: C3H8 + O2 C=3 H=8 O=2 H2O + CO2 C=1 H=2 O=3 Balancing Chemical Equations (2) Choose an Atom to Balance • Always leave H and O for Last • Start with an atom that appears as a single on either side (Products or Reactants) EXAMPLE Chemical Equation: C3H8 + O2 C=3 H=8 O=2 H2O + CO2 C=1 H=2 O=3 Balancing Chemical Equations (3) Add a Coefficient Number to the single atom to equal the amount of that atom on the other side. Don’t forget to adjust your numbers before continuing. EXAMPLE Chemical Equation: C 3H 8 + O 2 H2O + 3 CO2 C=3 H=8 O=2 C=1 =3 H=2 O=3 =7 Balancing Chemical Equations (4) Once you get to H and O, normally you will want to balance the Hydrogens before the Oxygens. Remember to adjust your numbers again before continuing. EXAMPLE Chemical Equation: C 3H 8 + O 2 C=3 H=8 O=2 4H2O + 3CO2 C=3 H=2=8 O = 7 = 10 Balancing Chemical Equations (5) Lastly balance the Oxygens. Remember to adjust your numbers again before continuing. EXAMPLE Chemical Equation: C3H8 + 5 O2 C=3 H=8 O = 2 = 10 4H2O + 3CO2 C=3 H=8 O = 10 Balancing Chemical Equations (6) Some equations will only balance by using ½ coefficients. But ½ atoms DO NOT exist. To Fix this problem simply DOUBLE ALL coefficients after you have the equation balanced. EXAMPLE Chemical Equation: 2FeS + 3½O2 S=2 Fe = 2 O=2=7 Fe2O3 + 2SO2 S=2 Fe = 2 O=7 Balancing Chemical Equations Notice that ALL products and reactants are still equal, but now there are no ½ atoms. EXAMPLE Chemical Equation: 4FeS + 7O2 S=4 Fe = 4 O = 14 2Fe2O3 + 4SO2 S=4 Fe = 4 O = 14 Balancing Chemical Equations By making both sides of a chemical equation equal, it tells scientist what amount of REACTANTS are necessary to make a certain amount of the PRODUCTS. Let’s see if you can Balance this Equation: Identify any coefficient number for each item. _Zn + _2 HCl Zinc Hydrochloric Acid _ZnCl2 + _H2 Zinc Chloride Hydrogen Gas Balancing Chemical Equations A Chemical Reaction occurs when you combine Potassium Chlorate (KClO3) with a Gummy Candy (C6H12O6). What Products do you think will be made? KCl CO2 H2O Potassium Chloride Carbon Dioxide Water (Steam) Light Heat Balancing Chemical Equations Let’s see if you can Balance this Equation: Identify any coefficient number for each item. _4KClO3 + _C6H12O6 Potassium chlorate Glucose (sugar) _KCl + _6CO2 + 6_H2O 4 potassium chloride Carbon dioxide Water