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Name____________________________ Conservation of Mass Reading Guide Page 78: During the 1780s the French chemist Antoine _________________________ showed that _________________________ can never be __________________________ or ________________________. Page 79: What does the Law of Conservation of Mass state? Page 80: Chemical ____________________________ can be described by chemical ______________________. Chemical _________________________ represent how ____________ are rearranged in a chemical reaction. When you write a chemical equation, the ________________________ go on the left of the arrow and the ___________________________ go on the right. CH4 + 2O2 CO2 + 2H2O Remember from a previous lesson that this is an example of a combustion reaction. CH4 is methane; O2 is oxygen gas; CO2 is carbon dioxide; H2O is water) List the 2 reactants in this reaction: ________________________________ List the 2 products in this reaction: ________________________________ The coefficients (big numbers in front of chemical formulas) show how many molecules are present in a reaction and the subscripts (small numbers after element symbols) show how many atoms of that element are present in each molecule (but only for the element directly in front of the subscript). If there is no number present, it is understood to be one. Examples: 2H2O CH4 -This shows 2 molecules of water. Each one has 2 atoms of hydrogen and one atom of oxygen -This shows 1 molecule of methane. The molecule has 1 atom of carbon and 4 atoms of hydrogen The get the total number of atoms of a specific element present on one side of the reaction, multiply the coefficient by the subscript and then if the element is listed more than once, add those numbers together. In this example ONE molecule of methane (CH4) and TWO molecules of oxygen gas (O2) react to form ONE molecule of carbon dioxide (CO2) and TWO molecules of water (H2O). One the reactants side (left) we have 1 atom of carbon, 4 atoms of hydrogen and 4 atoms of oxygen (2 molecules that each have 2 atoms of oxygen: 2x2=4). On the products side we have 1 atom of carbon, 4 atoms of hydrogen (2 molecules of water that each have 2 atoms of hydrogen: 2x2=4), and 4 atoms of oxygen (2 atoms in the carbon dioxide plus 1 atom in each of the 2 molecules of water). This shows that mass has been conserved. We have the same amount of each type of atom on each side of the chemical reaction. Every chemical equation should reflect this same thing. How many molecules of H2 are there?_______ How many molecules of O2 are there?________ How many molecules of H2O are there?________ In one molecule of H2O, how many hydrogen atoms are there? ________ In one molecule of H2O, how many oxygen atoms are there? _____ Element Total number of atoms present on reactant side Total number of atoms present on product side Oxygen (O) Hydrogen (H) Does this equation show that mass has been conserved (do you have the same total number of each atom in the reactants and in the products)? ___________________________________________________________ 6CO2 + 6H2O C6H12O6 + 6O2 This is the chemical equation for photosynthesis. CO2 is carbon dioxide; H2O is water; C6H12O6 is glucose; O2 is oxygen gas) How many molecules of carbon dioxide are present?______ How many molecules of water are present? ______ How many molecules of glucose are present? ______ How many molecules of oxygen gas are present? ______ Element Total number of atoms present on reactant side Total number of atoms present on product side Carbon (C) Oxygen (O) Hydrogen (H) Does this equation show that mass has been conserved (do you have the same total number of each atom in the reactants and in the products)? ___________________________________________________________ 3Fe + 4H2O 4H2 + Fe3O4 Element Total number of atoms present on reactant side Total number of atoms present on product side Fe H O Does this equation show a conservation of mass (same number of atoms) on both sides? _____ 4Al + 3O2 2Al2O3 Element Total number of atoms present on reactant side Total number of atoms present on product side Al O Does this equation show a conservation of mass (same number of atoms) on both sides? _____