Investigation I - Defining Matter Lesson I -A Penny For Your Thoughts

Do you think the alchemistswere successful?Explainwhy or why not. (Ifthis were possible, there wouldbe a lot of gold around -many peoplewould be rich, or gold wouldnot be worth verymuch!)

Do you think it is possiblenow to turn other metals into gold? (Yes,scientistscan do it, but it requires nuclear fission or fusion, which is verydifficult and expensive.)

The goal of this discussion is to find out what students know coming into your class. Theymay already be aware that ordinary things cannot be changed into gold without a great deal ofeffort and money, but they may not fully understand why. At this stage just accept their ideasmmujudgment. There will be plenty of opportunity for the students to gather their ownevidence and refine their ideas during this course.Be aware that student discussions are often more limited on the first few days of class,especially if the students feel they are being judged. Let your students know that you want toknow what they think so that you can better assist them in exploring their ideas.

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3. Explain the purpose of today's activity.If youwish you can write the main questionon the board.Points to cover:Tell students that youwill guide them in doing an experiment that is similar toone done by alchemists hundredsof years ago in their search for the key tomaking gold.While doing the experiment, students shouldgather evidence toaddress the question, "Can we turn a penny into gold?" Warn students thatpart of the reason you are guiding them through this lab is because it involvesdangerouschemicals, so they should pay close attention to your instructions. ~

Activity -A PennyforYourThoughts (15 min)This experimentcan be done in teams of two to four, depending on theamount of space and equipment you have. There are two parts: 1) reactingpennies in a hot mixtureof zinc and sodiumhydroxide (to turn them silver),and 2) heating the pennies in the flame of a Bunsen burner (to turn themgold).This lesson is designed to enable the teacher to direct the lab in a step-by-stepfashion, introducing equipment,experimentalprocedures, safetyconsiderations,and substances,as needed.Alternatively,all or part of thisexperimentcan be done as a demonstration. (Note: Don't give away theresults. Students get reallyexcited when they observe the copper penny turninto a gold penny.)

4. Introduce the class to their equipment. (Worksheet)Have a set of the appropriatelab equipment for today's class at the front of theroom so that you can demonstrate its use as you proceed through theexperiment. Pass out student worksheets - students can follow along as yougo over the procedurewith the class. (Note: You will need the "goldenpennies" for Lesson 1-4,so be sure to collect them.)

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Investigation 1- Defining Matter Lesson I-A Penny For YourThoughts

' /Equipment per team of 4 students:Safety gogglesPennyPaper towels2 tongs2 1O0-mLbeakers1 250-mL beaker half-filled with waterZinc filings Gust enough to cover the bottom of the 1O0-mLbeaker, -10 g»25-mL 3M sodium hydroxideHot plateBunsen burner (plus matches or strikers)Cold water (tap water is fine)

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5. Share safety tips with students.Hold up the pieces of equipment as you introduce them and explain theirappropriate use.Points to cover:Show students the safety goggles. Instruct them on where they are stored inthe class, and how to adjust them. Tell students they MUST WEAR SAFETYGOGGLES AT ALL TIMES when working in a chemistry laboratory. Todayit is especially important to do so, because they will be working with sodiumhydroxide, which is caustic and WILL BURN SKIN, EYES, OR CLOTHINGif it comes in contact with them. Advise students to rinse any spills withsignificant amounts of water and to notify you immediately. Tell students theywill be working with an open flame today. Let students know the dangers ofworking with an open flame (keep hair tied back and loose clothing awayfrom flame).Students will probably be excited and a bit nervous about the prospect of doing chemistry onthe first day of class. This is good. They will probably be more attentive about how they usethe laboratory equipment. If you choose to demonstrate the experiment, you should stillintroduce the equipment that will be used.

6. Complete the rIrst part of the experiment - "silver" the penny.Again, stress safety in this part of the experiment. Share any pertinentinformationabout the use of hot plates.Demonstratehow to use the tongs tohold the beaker. If youwish you can prepare beakers containing zinc filingsand sodiumhydroxide, before class. You can use these samebeakers for allyour classes.Points to cover:1. Tell students to placeenough zinc filings in a 100mL beaker to cover thebottom.

2. Ask them to carefullyadd 20 mL of 3M sodium hydroxide to the samebeaker.

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Investigation 1- Defining Matter Lesson I-A PennyFor YourThoughts

3. Instruct students to place the beaker on a hot plate which has been set to"4". If the liquidbegins to boil they should turn down the hot plate a little.

4. Tell students to use their tongs to pick up the penny and place it in thebeaker.

5. Once the penny is coated, tell studentsthat one teammember shouldholdthe hot beaker with tongs,while another removes the penny with a secondpair of tongs.

6. Tell students to put the hot penny in the 250 mL beaker, which is half-filledwith cold tap water.This serves to cool and rinse the penny.

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7. Complete the second part of the experiment - turn the penny "gold".Take some time to explain how to set up and light a Bunsen burner.Points to cover:1. Show students how to attach the rubber tubing to themethanegas outlet and the Bunsen burner.

2. Demonstratethe lightingof the Bunsen burner.3. Show students how to adjust the flame on the burnerusing the metal collar.A blue flame is hotter than ayellowor orange flame.

4. When teams are ready, ask them to light their burners.Walk around the room and check to see that all havecompleted this step successfully.

5. Tell the students to use their tongs to place the "silvered"penny into the flameof the Bunsen burner.

6. Tell students to hold the penny in the flame only until it changes color,and no longer. Pay attention, it happens quickly (within about tenseconds)!

7. Once the penny has changed color, ask students to place it in a beaker ofcold water to cool.

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8. Clean up.Instruct students to place their beakers of sodium hydroxide and zinc in thefume hood for the next class to use. Direct a general clean up of the lab area.

9. Complete the student worksheets.Once studentshave completed the experiment tell them they can work in theirteams to discuss the variousquestions and answer them. Every student shouldanswer the questions individually,even though they were discussed as a team.The following text is on the studentworksheets:Answer the following questions:1. Describewhat you observedduring the experiment.2. What do you think happenedto turn the penny silver?

Alchemy @DC Regents, LHS Living by Chemistry, 2003

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Investigation 1- Defining Matter Lesson l-A PennyFor YourThoughts

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3. What do you think happenedto turn the penny gold?Making SenseDo you think you madereal gold? How could you find out?

Making Sense Discussion (10 min)

Major goals: Open the discussionby asking studentswhat they observed. Focus onstudents' speculationsregardingwhether or not gold was really produced, and howwe could determinewhat happened.Some historicalbackground about alchemyshould also be introduced.

10. Discuss the findings.Discussiongoals:Focus the discussion on the students' observations about whathappened in the experiment.

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Samplequestions:Describewhat you observed during the experiment.What do you thinkhappened to turn the penny silver?What do you think happenedto turn the penny gold?Do you think youmade real gold?Why or why not?How could you find out?

Students may have a variety of explanations for what happened. Some may realize that thepenny is being coated with zinc during the first step of the experiment. Encourage students tothink about how to show that the golden substance formed (brass) and real gold are not thesame substances, even though they look similar.

11. Relate today's activity to the Alchemy Unit.Use this discussion to begin to flesh out the context that will drive theinvestigation into matter.Discussion goals:Explore the questionof whether or not gold was produced today.Samplequestions:Do we knowwhetheror not gold was produced in today's class? Explain.How do you think the alchemists decidedwhether or not somethingwasgold? (if it looked like gold and had gold's properties)What questions do you have about what happened to the penny?Points to cover:We did not determine if gold was made in today's activity.Nevertheless,wecan easily guess that we were unsuccessfulbecause it wasjust "too easy". Ifgold could be made in a high school chemistry class, then everyonewouldbevery wealthy.We need to explore further in order to find out if chemistscan

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Investigation 1- Defining Matter Lesson I-A Penny For Your Thoughts

make gold from other substances. The first step will be learning more aboutwhat all substances are made up of.

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12. Share information about alchemy. (Optional)Some information to share:The ancient art of alchemyhas been traced to China, the MiddleEast, Greece,and Egypt. A more contemporarypursuit of alchemy occurredduring theMiddleAges in Europe.Most of us are acquaintedwith images of wizards andsorcerers from this later time period. While alchemistsweremainly interestedin turninginexpensivemetals (like lead) into gold, they couldn't help butlearn a little bit about chemistry while they were in the laboratory.The earlyalchemists'pursuitswerenotsuccessful- they were never able to turnordinary substances into gold, although they tried for centuries. Even somefamous scientists, like Sir Isaac Newton, were involved with alchemy.Theirendeavorswere not entirely useless - manyexperimental techniques that arestill used in chemistry todaycame from the practice of alchemy.A lot of mysticism and spiritualitybecame associatedwith certain forms ofalchemy. Some alchemistswere searching for something called the Elixir ofLife, which they believedwould grant immortality and health.Otherssearchedfor the Philosopher's Stone,which was believed to be the object thatwould assist in transformingsubstances into gold. Chinese alchemy branchedinto two main disciplines."Waidan", or external alchemy, focused on themanipulationof natural substances. "Neidan", or internal alchemy, focusedonthe developmentof the individual into a more enlightenedbeing, and the questfor immortality.It must have been extremelydifficult for alchemists and early scientists tofigure out what was going on with chemicalchanges. Over the course of theyear we will be exploringin depth how to identify substances and understandchanges they undergo.

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Check-in13. No Check-in for this lesson.

14.No wrap-up

HomeworkNo homework on the first day of class.

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