Investigating & Explaining Ethanol Burning Carbon TIME Investigating & Explaining Ethanol Burning

Entry Task Have Out: Molecular Models, Evidence Based Arguments, Explanation Tool Read the “Three Questions” Tool We’ve been using these questions to guide our thinking Notice the Atom Facts related to each question Review how macroscopic evidence tells us about atoms

Burning Ethanol Experiment Similar Procedure as Soda Water Fizzing: Pour BTB into a control and experiment dish Weigh Ethanol dish before burning Light Ethanol IMMEDIATELY cover with hard plastic container LEAVE COVERED for at least 20 minutes

Evidence Based Argument Tool With a neighbor, For the Movement Question: “Where are atoms moving?” Compare the evidence you use and your conclusions What is the same? What is different?

Evidence Based Argument Tool With a neighbor, For the Carbon Question: “What is happening to carbon atoms?” Compare the evidence you use and your conclusions What is the same? What is different?

What unanswered questions do we have? Does mass data tell us about the movement of atoms? Does the BTB data tell us about the carbon atoms? while mass changes provide good evidence to answer the Movement Question, the BTB evidence provides only a partial answer to the Carbon Question The BTB results show that carbon ends up in CO2 in the air, but it does not explain where the carbon came from in the soda water the substance in soda water is that is the source of the carbon dioxide is carbonic acid.

Explanations Tool: Remember what we learned in the modeling activity about this chemical reaction!

What happens to atoms when soda water decomposes? Carbon Dioxide Products Chemical change Credit: Craig Douglas, Michigan State University Carbonic Acid Reactants Water

What happens to carbon atoms when soda water decomposes? Carbon Dioxide Products Chemical change Credit: Craig Douglas, Michigan State University Carbon atoms in soda water become part of carbon dioxide molecules. Carbonic Acid Reactants Water

What happens to oxygen atoms when soda water decomposes? Carbon Dioxide Products Chemical change Credit: Craig Douglas, Michigan State University Focus on oxygen atoms Oxygen atoms in soda water become part of water and carbon dioxide molecules. Carbonic Acid Reactants Water

What happens to hydrogen atoms when soda water decomposes? Carbon Dioxide Products Chemical change Credit: Craig Douglas, Michigan State University Focus on hydrogen atoms Hydrogen atoms in soda water become part of water molecules. Carbonic Acid Reactants Water

What happens to atoms when soda water decomposes? Carbon Dioxide Products Chemical change Credit: Craig Douglas, Michigan State University Focus on the Rule that “Atoms last forever” Atoms last forever! Carbonic Acid Reactants Water

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: [reactant molecule formulas] [product molecule formulas] Saying it in words: Chemists read the arrow as “yield” or “yields:” [reactant molecule names] yield [product molecule names] Equations must be balanced: Atoms last forever, so reactant and product molecules must have the same number of each kind of atom Try it: can you write a balanced chemical equation to show the chemical change when soda water loses its fizz?

Chemical equation for soda water losing its fizz H2CO3  H2O + CO2 (in words: carbonic acid yields water and carbon dioxide)

How have our ideas changed? What scales do you use to explain Soda Water Fizzing now? What scales did you use at first? How are your explanations of the movement of atoms different? How are your descriptions of the movement of carbon different? What do you know now that you didn’t know before the investigation?

Investigating & Explaining Ethanol Burning Review the ideas and questions we had at the beginning of this unit…

Two Questions about Chemical Change What is a chemical change? A change in matter where atoms are rearranged into new molecules. Questions scientists always try to answer about chemical changes involving carbon atoms: The Movement Question: Where are atoms moving? The Carbon Question: What is happening to carbon atoms? Notice that each question is accompanied with “rules to follow” as well as ways to “connect atoms to evidence.”

The Energy Question Two facts about energy: Energy lasts forever. Energy is never created or destroyed in chemical changes. Energy can be transformed from one form to another. What do you know about forms of energy? List some common forms of energy.

The Energy Question What is happening to chemical energy? What forms of energy are involved? How is energy changing from one form to another?

With a Neighbor Share your thoughts about Ethanol Burning Compare your predictions about the 3 questions

What Are Your Ideas about the Movement Question? Where are atoms moving from? Where are atoms going to?

What Are Your Ideas about the Carbon Question? What molecules are carbon atoms in before the change? What other molecules are involved? What molecules are carbon atoms in after the change? What other molecules are produced?

What Are Your Ideas about the Energy Question? What forms of energy are in the reactants? What forms of energy are in the products?

Record Data Observe Changes to Your Ethanol & BTB Record changes in mass and color Share your observation on the class data sheet

Possible BTB Colors Photo Credit: FableVision

Comparing Group Results Results for mass changes What patterns are there in measurements made by all the groups? Do the patterns match your predictions? Results for BTB changes What patterns are there in observations made by all the groups? Do the patterns match your predictions?

Ethanol Burning Video Conclusion

Results for Ms. Angle’s Class Trial # Initial mass of ethanol (g) Final mass of ethanol (g) Change in mass of ethanol (g) start BTB color end BTB color 1 67.80 66.8 -1.00 blue yellow 2 50.63 49.43 -1.20 3 63.22 62.54 -0.68 4 57.23 56.59 -0.64 5 62.01 61.21 -0.80 6 57.37 56.73 Photo Credit: Michigan State University How do your results compare with the results for Ms. Angle’s class?

Evidence of CO2 in Air from Burning 4 minutes 8 minutes 10 minutes, with control Photo Credits: Michigan State University

Results vs Predictions Look at your predictions tool: Which of your predictions were supported? Which predictions were not supported? What questions do we still need to answer?

With a Partner: Review the pattern we observed in the BTB color change Review the pattern we observed in the mass change for ethanol Use these patterns to explain what happened during the investigation: Where are atoms moving? Evidence? What is happening to carbon atoms? Evidence? What is happening to chemical energy? Evidence?

HINT: Use this discussion to help you complete the “Evidence Based Arguments Tool” As Homework

Homework: Complete “Evidence Based Arguments Tool: What happens to Ethanol when it burns?” Make flashcards for the 3 Atom Facts and the 2 Energy Facts Review those flashcards to help you learn the facts.