Brief Overview. Teaching Goals. Agenda. Lesson Introduction. The Soda-Mentos Reaction

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Alison Ramsey
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1 The Sda-Ments Reactin Lessn Type: Mdule Target Grade: Elementary Authr: Siddarth Krishna Semester: Spring 2013 Brief Overview In this lessn, students will learn abut the prperties f sda and will use scientific investigatin t figure ut what causes sda t react with ments candy. Teaching Gals Scientific methd plan, experiment, analyze results, experiment again, and draw cnclusins T determine the basic prperties f sda, ments, and the gas in the sda which cause the ments-sda reactin t happen. T have fun playing with sda and ments Agenda Intrductin: What is sda? Investigating the Gas: Ments-Sda Dem Investigating the Sda: What wrks and why Investigating the Ments: Surface prperties Lessn Intrductin Intrduce what sda is t the students: water, sugar, and fizz. Alng the way we ll ask what they think is in sda, etc. Then we ll talk abut what the students think fizz is (we ll tell them at the end it s disslved CO2 gas). Then we will dem the ments and cke reactin ut f a 710 ml bttle. We will capture the CO2 released in a balln, allwing kids t see that the captured gas is nt regular air. We will tell the students that the lessn will be fcused n ding an investigatin, using scientific skills t figure ut what is ging n in the ments sda reactin and what causes it t happen. We will then split the students int grups and have them investigate the different prperties f the sda, lking at the prperties f bth the ments and the sda.

2 Mdule 1: Gas Investigatin Intrductin Fr the students t determine what kind f gas is released in the reactin. A demnstratin f the sda-ments reactin will be dne, inflating a balln which the students can play with t determine that a gas is released in the reactin which is heavier than air. 4 uninflated ballns Tw 710 ml sda bttle (2x, in case the first ne desn t wrk) One ments per sda bttle Material t Teach We wuld like t first give the kids an intrductin t the exciting reactin that ccurs between ments and sda. The first thing they shuld see is that sme kind f gas is released in the reactin which we can capture in a balln t study. Mst imprtantly, the kids shuld see that it s different frm air. Prcedure fr Mdule 1 After the intrductin, gather all f the students in a circle, preferably utside s it desn t make a mess. Put ONE ments inside f a deflated balln, and place the balln ver the neck f a 710 ml sda bttle. Make sure t ask the kids what they think will happen. Then, carefully verturn the balln until the ments falls in, taking care t keep the sda bttle upright and the balln vertical. Als, prepare a regular muth-blwn air balln, which will be fr cmparisn with the CO2 balln. Make it the same size as the CO2 balln. Observe the balln inflating and ask the kids what they think is ging n. It shuld be bvius that sme gas is being released by the reactin. The questin is, what gas? Tie ff the balln carefully. Allw the kids t pass the balln t each ther, hlding it and testing it relative t the air balln. They shuld see that the CO2 balln drps mre rapidly in air (due t its higher density) than a regular air balln des. Ntes fr Mentrs When the reactin happens the balln will inflate t abut half f its full inflatable size. Liquid will fire int the balln just hld it vertical and the liquid will drain back dwn (if yu dn t, the weight may make the balln break ff frm the sda neck). CO2 has a mlecular weight f 44 g/ml, cmpared t 29 g/ml fr air. Our breath has CO2 in it, but nly abut 5%, s it will nt be as heavy as the CO2 balln. The CO2 balln als has sme air in it (which was initially in the sda bttle). Overall, the CO2 balln will fall abut 20% faster than the air balln (it wrks!)

3 If the students are cnfused abut why ne balln flats and anther sinks, make an analgy with water things flat in water when they are lighter (less dense) than water, and sink when they are heavier (mre dense) Mdule 2: Sda Investigatin Nte: The fllwing tw mdules will be dne in 2-3 grups, indrs. Intrductin Fr the students t determine whether it is the fizz r the sugar in sda that causes the reactin. The students will experiment with the different ingredients f sda t discver what prperty f the sda causes the ments-sda reactin t ccur, and hw the effect can be lessened r strengthened. A few cups Regular sda, plain water, plain sugar, and sparkling water (sugarless) Mint Ments A few sheets f paper Material t Teach After we tld the kids that sda has three main ingredients: water, sugar, and fizz, we nw give the kids each f these ingredients separately, s they can play with each ne and see whether the ments reactin wrks with each ne. They shuld cnclude that sugar has little r n effect n the reactin, but rather, fizz is what matters t the reactin. Thrughut the lessn, the kids shuld use their varius senses (nt taste) t analyze what they are seeing. They shuld be able t see the gas bubbles leaving the ments surface, hear the fizz cming ut, etc. Prcedure fr Mdule 2 This ne is easy t prepare fr. Mentrs shuld fill up the red cups t their mid-lwer line (150 ml) based n what the students want t test. Mentrs need t be a supprting rle t the teams f students as they cnduct experiments, and as they try t analyze their results. Mentrs shuld encurage students t try different things with the tls in frnt f them (fr example, try diluting the sda with water and see if the reactin is as strng), etc, withut giving away the answers. The gal is t get kids t analyze a prblem they haven t seen befre, and use their bservatins and experiments t figure ut what is ging n. The mentrs shuld make sure t include all students in the grup activity. The students can write dwn their bservatins/cnclusins etc n a piece f paper as they g alng.

4 Ntes fr Mentrs The mentrs shuld understand that it s the fizz that causes the reactin t happen. One interesting thing is that if yu add plain sugar (n ments) t sugar water, the sugar itself causes a ments-like reactin when it is drpped in. The sugar crystals can act as nucleatin sites just as the rugh surface f the ments d. If the kids discver this, they will definitely find it hard t explain - s mentrs shuld encurage them t think abut it, but nt t just cnclude that it is sugar that causes the reactin (which wuldn t make sense, since the sda is already s sugary!) Mdule 3: Ments Investigatin Intrductin Fr the students t determine what prperties f the ments cause them t react the way they d. Students will experiment with regular ments versus special, smthed-ut ments which n lnger have a rugh surface. They will find that the smth ments dn t perfrm the reactin, and can bserve the surface rughness versus smthness with a magnifying glass. Students shuld cnclude that the rugh surface f the ments plays a part in the reactin. Ments Ments which have been put in water and micrwaved fr 1 min, then taken ut and left t cl vernight Sda Magnifying glass Material t Teach Here we investigate what in the ments causes it t react the way it des. We prvide students with regular ments, cmpared t ments that we have prepared which are melted (the surface is nw visibly smth).we als give kids a magnifying glass s they can examine the ments surfaces mre clsely. The kids shuld hpefully see that it is nt sme chemical in the ments interir that causes the reactin rather it has t d with the rugh surface. If yu bserve the ments while it is in the sda, yu can see CO2 bubbles frming n the surface and leaving hpefully this shuld tip the students ff that the surface facilitates the fizz leaving the sda. Prcedure fr Mdule 3 Fairly simple just lay ut the different materials, explain what they are, and let the kids experiment. Mentrs shuld facilitate their experimentatin and discussin f the results Ntes fr Mentrs

5 The science: the rugh surface f the ments prvides nucleatin sites areas where CO2 bubbles can frm easily (due t lwered surface tensin, etc), allwing them t be frmed rapidly. When they are frmed, they flat up and are released, allwing mre bubbles t be frmed cntinuusly. Remember that nce the sda bttle is pened, the system will tend twards releasing fizz frm the sda since it was previusly ver-pressurized with CO2. The ments surface (and many ther rugh surfaces) just acts as a physical catalyst, speeding up the release f CO2. Cnclusin: At the end, briefly discuss with the students what they learned during the lessn, and what they think is ging n in the ments-sda reactin. Tell them that it is the sda s fizz which is being released as a gas, and that the rugh surface f the ments that causes this release t happen. Hpefully they figured mst f that ut already! References

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