1. Lesson 4 Activity 3 Using Molecular Models for Ethanol 1

2. ZOOMING INTO A 2

3. 3 Oxygen Carbon Dioxide Water Ethanol What’s the hidden chemical change when ethanol burns? ?

4. The bottom of flame at atomic-molecular scale 4

5. The top of flame at atomic-molecular scale 5

6. Reactants Products Chemical change What happens to atoms and energy when ethanol burns? Ethanol Oxygen Water Heat and light energy Carbon Dioxide

7. How Atoms Bond Together in Molecules Atoms in stable molecules always have a certain number of bonds to other atoms: Oxygen atoms do NOT bond to other oxygen atoms if they can bond to carbon or hydrogen instead. Chemical energy is stored in bonds between atoms 7

8. Making the Reactant Molecules: Ethanol and Oxygen The flame of burning ethanol comes when ethanol (C 2 H 5 OH) reacts with oxygen (O 2 ). Make a molecules of ethanol and oxygen on the reactant side of your Molecular Models poster. Follow along with your worksheet… 8

9. 9 Photo of reactant molecules: C 2 H 5 OH (ethanol) and O 2 (oxygen) Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away) ReactantsProducts Chemical change Ethanol with chemical energy Oxygen

10. Rearranging the Atoms to Make Product Molecules: Carbon Dioxide and Water The flame of burning ethanol comes when ethanol (C 2 H 5 OH) reacts with oxygen (O 2 ) to produce carbon dioxide (CO 2 ) and water (H 2 O). Show how this can happen: Follow along on your worksheet… 10

11. 11 Photo of product molecules: CO 2 (carbon dioxide) and H 2 O (water) Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away) Reactants Products Chemical change Heat Light Water Carbon dioxide

12. 12 Comparing photos of reactant and product molecules Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away) Reactants Products Chemical change Ethanol with chemical energy Oxygen Heat Light Water Carbon dioxide

13. Reactants Products Chemical change Ethanol Oxygen Water Heat and light energy Carbon Dioxide What happens to carbon atoms when ethanol burns? Carbon atoms in ethanol become part of carbon dioxide molecules.

14. Reactants Products Chemical change Ethanol Oxygen Water Heat and light energy Carbon Dioxide What happens to oxygen atoms when ethanol burns? Oxygen atoms become part of carbon dioxide and water molecules.

15. Reactants Products Chemical change Ethanol Oxygen Water Heat and light energy Carbon Dioxide What happens to hydrogen atoms when ethanol burns? Hydrogen atoms become part of water molecules.

16. Reactants Products Chemical change Ethanol Oxygen Water Heat and light energy Carbon Dioxide What happens to chemical energy when ethanol burns? Chemical energy is transformed into heat and light energy.

17. Reactants Products Chemical change What happens to atoms and energy when ethanol burns? Ethanol Oxygen Water Heat and light energy Carbon Dioxide Atoms last forever! Energy lasts forever!

18. Writing a Chemical Equation Chemists use chemical equations to show how atoms of reactant molecules are rearranged to make product molecules. Writing the equation in symbols: Chemists use an arrow to show how reactants change into products. Equations must be balanced: Atoms last forever. Try it: Can you write a balanced chemical equation to show the chemical change when ethanol burns? 18

19. 19 Chemical equation for ethanol burning C 2 H 5 OH + 3O 2  2 CO 2 + 3 H 2 O (in words: ethanol reacts with oxygen to yield carbon dioxide and water)

20. Can you answer the Three Questions for ethanol burning now? What are your ideas? The Location/Movement Question: Where atoms moving? The Carbon Question: What is happening to carbon atoms? The Energy Question: What is happening to chemical energy? 20

21. 21 What happens when ethanol burns? Remember: Atoms last forever and Energy lasts forever What forms of energy are in the reactants? What molecules are carbon atoms in before the change? What other molecules are involved? Where are atoms moving from? What forms of energy are in the products? What molecules are carbon atoms in after the change? What other molecules are produced? Where are atoms moving to? Chemical change