56 Chemical Reactions and EquationsLesson 1Scan Lesson 1. Read the lesson titles and bold words. Look at the pictures. Identify three facts youdiscovered about chemical reactions. Record your facts in your Science Journal.Understanding Chemical ReactionsCopyright © McGraw-Hill Education.Differentiate a physical change from a chemical change.Physical Change Chemical ChangeIdentify signs of a chemical reaction.••••••One way to becertain:Four changesin propertiesTwo changesin energySigns ofChemicalReactionSequence changes in atoms during a chemical reaction.Bonds betweenatoms break.Changes in MatterI found this on page.Signs of a ChemicalReactionI found this on page.What happens during achemical reaction?I found this on page.Recall that matter can undergo two typesof changes-chemical or physical. A physicalchange does not produce new substances. Thesubstances that exist before and after thechange are the same, although they mighthave different physical properties. This iswhat happens when liquid water freezes. Itsphysical properties change from a liquid to asolid, but the water, H,O, does not changeinto a different substance. Water moleculesare always made up of two hydrogen atomsbonded to one oxygen atom regardless ofwhether they are solid, liquid, or gas.Recall that during a chemical change, oneor more substances change into new sub-stances. The starting substances and the sub-stances produced have different physical andchemical properties. For example, whenbrownie batter bakes, a chemical changeOCcurs. Many of the substances in the bakedbrownies are different from the substances inthe batter. As a result, baked brownies havephysical and chemical properties that are dif-ferent from those of brownie batter.alan is called a cheminalChange of colorOdorFormation ofbubblesFormation ofprecipitationWarming orcoolingRelease oflightBonds form betweenhydrogen atomsBonds form betweenoxygen atoms Chemical Reactions and Equations 57Lesson 1 | Understanding Chemical Reactions (continued)Copyright © McGraw-Hill Education.Distinguish the parts of a chemical equation.Chemical Equationdescription ofto represent to representsubscripts describe theusingDetail information regarding the writing of chemical equations.Define reactant.Define product.Write the generalstructure for a chemicalequation.How is the arrow signread?Write the equation for“carbon plus oxygenproduces carbon dioxide.”Restate the law of conservation of mass.Conservation of MassI found this on page.I found this on page.Chemical EquationsI found this on page.z zA reactionElement symbols Chemical formulasElements CompoundsNumber of atoms of each elementThe starting substances in a chemical reactionThe substances produced by a chemical reactionReactant + reactant ——> product + productAs “produces” or “yields”C + O ———-> COThe total miss before a chemical reaction is the same as the total mass after a chemical reaction. 58 Chemical Reactions and EquationsLesson 1 | Understanding Chemical Reactions (continued)Copyright © McGraw-Hill Education.Relate atoms to mass in a chemical reaction.Mass before a chemicalreaction is equaltoNumber of atoms in thereactantsParaphrase what it means when you say a chemical equation isbalanced.Explain the meaning of chemical formulas. Circle the coefficient.H20 2H20means meansOrder the steps in balancing a chemical equation.1.2.3.4.Balance the chemical equation for carbon monoxide.C + O2 COLook back at the picture of the firefly on the first page of Lesson 1. How couldyou conclude that the firefly’s blinking is a chemical rather than a physical change simply byviewing the picture and without reading the text on the page?I found this on page.I found this on page.I found this on page.I found this on page.I found this on page.Number of atoms in the productsThe specific numbers of types of atoms are the same on both sides of the equationOne water molecule Two water moleculesWrite the unbalanced equationCount atoms of each element in the reactions and product’sAdd coefficient to balance the atomsWrite the balanced chemical equationThe firefly's blink gives