CHEMICAL EQUATIONS A chemical equation can be used to model a chemical reaction. Parts of a chemical equation: reactants products 2Na + Cl2 2NaCl arrow means “yields” or produces Law of Conservation of (Matter)Mass Matter cannot be created or destroyed in an ordinary chemical reaction. This means the mass of the reactants must be equal to the mass of the products during a chemical change. Coefficients are used to balance chemical equations. Never change the subscripts to balance a chemical equation. Count atoms to determine if a chemical equation is balanced: H2O = 1 molecule of water, 2 hydrogen atoms, 1 oxygen atom 3H2O = 3 molecules of water, 6 hydrogen atoms, 3 oxygen atoms Examples Reactants Products Balanced (Yes or No) 1. CuS +Ca CaS + Cu yes 2. CO C + O no 3. S8 + O2 SO3 no 4. FeCl3 + 3NaF FeF3 + 3NaCl yes Independent Work Directions: Determine the reactants and products in each chemical equation and tell if it is balanced or not. The first one has been done for you. Chemical Equation Reactants Products Balanced? (Yes or No) 1. Na + Cl2 NaCl Na + Cl2 NaCl No____ 2. C + O2 CO2 ___________________ ________________ ____________ 3. C + O2 CO ___________________ ________________ ____________ 4. C + H2 CH4 ___________________ ________________ ____________ 5. H2O H2 + O2 ___________________ ________________ ____________ Chemical Equation Reactants Products Balanced? (Yes or No) 6. Mg + 2O2 2MgO2_________________ ________________ ____________ 7. H202 H2 O + O2 __________________ ________________ ____________ 8. 2NaCl 2Na + Cl2 __________________ ______________ ___________ 9. Fe + O2 Fe2O3 __________________ ________________ ____________ 10. Ca + Cl2 CaCl2 __________________ ________________ ____________ Bell Ringer A day 11/, B day 11/ Question: What is the difference between a compound and a mixture? Answer: Compounds are made up of elements chemically combined. Mixtures are made up of substances not chemically combined. Warm-up #11, A day 11/, Bday 11/ Question: How many atoms of each element are present in this compound? H2SO4 Answer: hydrogen: 2 sulfur: 1 oxygen: 4 Get out a Blank Sheet of Paper Place a heading in the TOP RIGHT CORNER Title: Counting Atoms, Item # 16. Number your paper 1-5 and skip two lines between each. Determine the number of atoms in each compound Example: 5H2O hydrogen = 10; oxygen = 5 1. CaCO3 calcium = 1, carbon = 1, oxygen = 3 carbon=27, hydrogen=24, oxygen =12 2. 3C9H8O4 3. 5MgSO4 magnesium =5, sulfur = 5, oxygen=20 4. 8CH 4 carbon = 8, hydrogen=32 5. 3NaOCl sodium = 3, oxygen =3, chlorine =3 Examples Reactants Products Balanced (Yes or No) 1. CuS +Ca CaS + Cu yes 2. CO C + O yes 3. S8 + O2 SO3 no 4. FeCl3 + 3NaF FeF3 + 3NaCl yes Directions: Determine the reactants and products in each chemical equation and tell if it is balanced or not. The first one has been done for you. Chemical Equation Reactant Products Balanced? (Yes or No) 1. Na + Cl2 NaCl Na + Cl2 NaCl No 2. C + O2 CO2_________ _________ 3. C + O2 CO _____________________ 4. C + H2 CH4________________________ 5. H2O H2 + O2____________________ Chemical Equation Reactants Products Balanced? (Yes or No) 6. Mg + 2O2 2MgO2 __________ 7. H202 H2 O + O2 ____________ 8. 2NaCl 2Na + Cl2 ____________ 9. Fe + O2 Fe2O3 ____________ 10. Ca + Cl2 CaCl2 ____________ Chemical Reactions and Equations 1. Photosynthesis (plants making glucose) carbon dioxide + water glucose + oxygen 6CO2 + 6H2O C6H12O6 + 6O2 2. Respiration (breathing) glucose + oxygen carbon dioxide + water C6H12O6 + 6O2 6CO2 + 6H2O Heating sugar C12H22O11 + O2 CO2 + 11H2O + 11C Warm-up , A day 11/16, B day 11/17 • Is the following equation balanced? • S3 + O2 SO3 • Honors: If it is not balance, balance it. • Please take out your homework ws#11 Making Models of Molecules • Carbon – Black • Hydrogen – White • Sulfur - • Oxygen – 4 prongs » Blue .