2Section 11.1 Describing Chemical Reactions Objective 1: You will learn to identify when a chemical reaction takes place.Objective 2: You will know what the “Law of Conservation of Mass” means.Objective 3: You will be able to write both word and formula equations.Objective 4: You will know what all the different symbols used in writing chemical equations mean.
3How Do You Know A Rxn Has Occurred??? Heat and/or light is produced light and heat rxnProduction of gasFormation of a precipitateColor change precipitate and color change
4Law of Conservation of Mass Atoms are neither created or destroyedAntoine Lavoisier ( )
5Communicating a chemical reaction In a sentence every item is a word … Copper reacts with chlorine to form copper (II) chloride.In a word equation some symbols used …copper + chlorine ® copper (II) chlorideIn a formula all symbols used …Cu(s) + Cl2(g) ® CuCl2(s)
6All chemical reactions… have two parts:Reactants = the substances you start withProducts = the substances you end up withThe reactants will turn into the products.Reactants ® Products
7Symbols in equations? – Text page 323 the arrow separates the reactants from the products (arrow points to products)Read as: “reacts to form” or yieldsThe plus sign means “and”(s) after the formula = solid: Fe(s)(g) after the formula = gas: CO2(g)(l) after the formula = liquid: H2O(l)
8Symbols used in equations (aq) after the formula = dissolved in water, an aqueous solution: NaCl(aq) is a salt water solution used after a product indicates a gas has been produced: H2 ¯ used after a product indicates a solid has been produced: PbI2 ¯
9Symbols used in equations double arrow indicates a reversible reaction (more later)shows that heat is supplied to the reactionis used to indicate a catalyst is supplied (in this case, platinum is the catalyst)
10Enzymes are biological or protein catalysts in your body. What is a catalyst?A substance that speeds up a reaction, without being changed or used up by the reaction.Enzymes are biological or protein catalysts in your body.
11Write a skeleton equation for: Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form iron (III) chloride and hydrogen sulfide gas.Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate dissolved in water.