REACTING to Density GO TO YOUR NEXT OPEN PAGE AND PUT THE TITLE AND DATE ON IT. Slide 1

MATERIALS Empty plastic water bottle 1 antacid tablet – each table has a packet of 2 tablets 25 mL water Bottle cap OR balloon Scale Graduated cylinder Pipette Slide 2

Overview of Lab  Students used a plastic bottle, water, an antacid tablet to see what happens during a chemical reaction between antacid tablets and water.  The reaction is a closed system, meaning that once the cap or balloon goes on nothing can get in or get out.  You need to create before sketches (based on the next slide) and after sketches (based on the information provided).  You need a data table for 3 sets of masses for both set-ups: before the reaction; after the reaction and final mass (after the removal of the cap / balloon. Slide 3

Procedure 1.Measure 25mL of water, use the pipette to add or remove the last milliliter or so 2.Pour the water into the bottle 3.All of the following items go on the scale at the same time to be massed: ◦bottle with 25mL of water ◦1 antacid tablet ◦Bottle cap OR balloon (depending on which you are doing) 4.Record the mass of the set up before the reaction 5.Sketch the before set up of each (cap and balloon) see next slide Slide 4

4. Before Reaction Sketches BEFORE REACTION SKETCH—BOTTLE CAPBEFORE REACTION SKETCH--BALLOON Label all parts of the set-up: bottle, water, cap, etc. antacid Slide 5

Procedure, continued 6.Drop the antacid tablet into the water and put the cap or balloon on it very quickly. 7.Ensure the reaction is complete by shaking the bottle gently a couple of times. The reaction has stopped when all fizzing and bubbling is done. 8.Take the mass for after the reaction and record. Get the mass from the other pair too and record. 9.Sketch the after reaction set up of each (cap and balloon). 10.Take the cap or balloon off. Record any sounds you hear. 11.Take the final mass and record. Get the mass from the other pair too. ◦Should have 3 masses for the cap and 3 masses for the balloon. Slide 6

Reaction—this is what students who did the lab recorded. Use this information to complete your sketches and data table BOTTLE CAP—BEFORE MASS 40.4 g Student narrative (as if you were the student) I dropped the antacid tablet into the bottle and my partner quickly put the lid on it tightly. I saw bubbling and foaming as the tablet dissolved into the water. The bottle got firmer as the reaction continued. I had to shake the bottle a couple of times to be sure the reaction was still going on. Once the reaction was complete we took the mass again. AFTER MASS 40.4g I drew a picture of the after reaction identifying all parts of the set-up and noting the firmness of the bottle. BALLOON—BEFORE MASS 39.6g Student narrative (as if you were the student) I had the balloon stretched and ready to put on the bottle. My partner was holding the bottle and dropped the antacid tablet in. I immediately put the balloon onto the bottle. I saw bubbling and foaming in the bottom of the bottle. I also saw the balloon begin to inflate on the top of the bottle. My partner shook the bottle a couple of times to be sure that the reaction had stopped. The balloon inflated a bunch—it looked like a little balloon on the top of the bottle. The bottle wasn’t as firm as the bottle-capped bottle. AFTER MASS 39.3g I drew a picture of the after reaction identifying all parts of the set-up and noting the firmness of the bottle. Slide 7

Reaction—this is what students who did the lab recorded. Use this information to complete your sketches and data OBSERVATIONS—TAKING THE CAP OFF o What did you see or hear as the cap came off? I didn’t see anything—but I hear a hiss like when you open a bottle of soda. o Final Mass: 39.6g OBSERVATIONS—TAKING THE BALLOON OFF  What did you see or hear as the balloon came off? I didn’t hear much of anything, just the sound of the balloon coming off, maybe a tiny hiss of air. o Final Mass: 39.6g Slide 8

Displaying data  Create a data table to show the 3 masses for both the bottle-cap and balloon portions of the lab.  Be sure to have column headings and row headings.  Remember that your numbers must have units Slide 9

Change in Mass o This was a closed system—so there shouldn’t be a change in mass between before reaction and after reaction. If there is a difference and it is less than 0.5g treat the masses as nearly the same. o The loss of mass occurred because the cap or the balloon wasn’t put on quickly enough or tight enough. o Calculate the change in mass by subtracting the final mass from the after reaction mass. o change in mass = final mass – after reaction mass Slide 10

Post Lab Questions copy and answer OR restate the question in the answer 1.Compare your before and after reaction masses, are they the same or nearly the same? As long as they are within 0.5g of each other they are nearly the same. 2.What was the difference in mass from after reaction to final mass? 3.Did you see or hear anything escape from the bottle? 4.What phase of matter was whatever that escaped? 5.Is the substance that escaped matter? How do you know? 6.What do you think the substance that escaped was? Slide 11