Alka-Seltzer Rockets

[Image one: A film canister with its lid on.]

[Image two: A picture of a film canister upside down about to launch.]

Objective:

1. Identify that an explosion is only as strong as the container it is in.

2. Compare 4 different combinations of Alka-Seltzer and water in a film canister in terms of their explosive force and time to explode.

3. Propose mechanism/mechanisms to explain the experimental data.

Prerequisite Knowledge:

Fractions [halves and quarters]

Pressure

Chemical reactions

NSTA Science Process Skills:

Observing students observe the different explosions.

Measuring students measure height of launch and time to explode.

Infer students use their data and observations to infer the pressure build up process within the film canister.

Predict students predict the outcome of the experiment given and their own experiment.

Experiment students conduct a 2 variable, controlled experiment and analyze its results.

Accessibility: [Specific changes to procedure in blue parentheses]To measure height:

Attach a fishing line to the rocket securely. Allow the spool to spin freely. As the rocket ascends the spool will measure its distance.

Attach a whistle to the film canister. It will produce sound on the way up and on the way down. This allows for a qualitative measurement of height.

Talking stopwatches to measure time.

What You Need:

Goggles 1 per

Alka-Seltzer, in individual packages 2 per + 4

Film canisters with lids 1 per 2 link

Stopwatches 1 per 2 (talking stopwatches)

Clipboards 1 per 2

Pencils 1 per 2

Tumbler, plastic 9 fl. Oz. 1

Ice cream buckets 2

AlkaSeltzerRocketHandout.docx (Braille, large print, and accessible copies) 1 per 2

Dowel, straw, or soft pen casing, notched with scissors at 1/3rd or 2/3rd height of film canister 1 per 2

Fishing line on spool 1 per 2 OR whistle 1 per 2

Document showing the possible water/Alka-Seltzer combinations, Braille, large print, and accessible copies 1 per 2

For differentiation option 3: Sensational Blackboard - 1

What You Do:

1. Tell students, We are going to use a chemical reaction to power a rocket. Open a package of Alka-Seltzer and place a tablet into water. Direct students to observe the reaction.

a. Ask, What did you observe? [fizzing, bubbles, hiss sound] Is this an explosion? [Students will have a variety of answers.] There is no buildup and release of pressure so there is no explosion. Technically each bubble is an explosion.

2. Hand out the stopwatches (talking stopwatches) and invite the students to practice using them for the next demonstration. Students should press start when they hear the lid close and press stop them when they hear the canister explode.

3. Place some warm water [about 2/5ths full] into a film canister. Explain, The trick is to put the tablet in and cover it as quickly as possible with the lid until it snaps shut. Demonstrate how to pinch the lid to the film canister between your thumb and forefinger and a tablet of Alka-Seltzer pressed against the palm of the hand with ring and pinky [emphasize this holding as it is one of the only ways to hold everything without a partner]. (Use hand under hand technique to demonstrate the holding technique.)

4. Direct students to put on their goggles. Drop the tablet in and cover it as quickly as possible. Place the sealed film canister lid down on the table. Explain, The tablet reacts with water and makes a gas. That gas cant get out of the canister so it builds up pressure. During this time the film canister will explode dramatically and hit the ceiling.

5. Ask, Where does the pressure release from? [the canister or the lid] Ask, How many seconds did it take?

6. Explain, The explosion is only as strong as the container it is in. Film canisters can hold a lot of pressure if their cap is snapped on.

7. Say, Although this explosion is cool, we will be analyzing it scientifically. There will be four experiments [draw them with their numbers on the board]:

Experiment Diagram: Image of a diagram of the four trials of the experiment.

1: 1/3 water + Alka-Seltzer

2: 1/3 water + Alka-Seltzer

3: 2/3 water + Alka-Seltzer

4: 2/3 water + Alka-Seltzer

For each experiment the students need to record two things, time to explode and height of the rocket. Time is to be recorded from the time the top of the film canister is sealed to when it explodes (talking stopwatches). Height is to be recorded as low [to knee], medium [doesnt hit ceiling], and high [hits ceiling]. (Direct students to attach a fishing line to the film canister with a knot, ring of tape, or both. Allow the spool to spin freely OR tape whistle to side of spool.)

8. Record predictions of which experiment students think will go the highest and take the longest to explode on the board by show of hands. (Have students do a voice vote, say aye, in addition to raising their hands.)

9. Group students into pairs by some expedient means. Students should switch the person using the stopwatch and the person launching the rocket after each experiment.

10. Pass out the materials. Direct students to practice the Alka-Seltzer dropping technique without water in the film canister.

11. Line students up to take them outside [If conducting experiments indoors a kiddie pool can serve as a launch site to minimize the mess]. Take two ice cream buckets of water outside and some extra Alka-Seltzer tablets.

12. After the students have completed the four experiments, hand them a second full package of Alka-Seltzer and direct them to do any experiment they want to do as long as they write down what they do and the results.

13. As students finish their experiments, give the class a final launch signal and once the last rocket has fired, direct students to clean up the Alka-Seltzer wrappers and gather their materials to return inside.

14. After students return to the room, ask:

a. Which combination went the highest? Take votes then ask why that one could have gone the highest.

b. Which combination took the longest? Take votes then ask why that one took the longest.

The responses are typically: space to build up pressure, amount of Alka-Seltzer, and the Alka-Seltzer rockets mass [prompt if needed].

14. If time permits ask the students to report on the other experiments they did.

15. Direct students to rinse their film canister and lid, then return the other materials to you or some convenient location.

Data Table:

Experiment #

Time to pop (sec)

Rocket height (Low, Med, High)

1

2

3

4

Student Questions:

1. Write the experiment numbers in order from lowest height to highest height.

2. Why do you think some rockets went low and some rockets went high when they exploded?

3. Write the experiment numbers in order from shortest time to explode to longest time to explode.

4. Why do you think some rockets take a long time to explode and some rockets take a short time to explode?

5. Draw 2 pictures of what is happening inside the film canister after the Alka-Seltzer and water combine and the lid is snapped on; one where it exploded a little and one where it exploded a lot. Label the parts of your drawing.

Differentiations and Extensions:

1. Add free fall calculations. Students can calculate the height of the rockets flight by measuring the time it takes to descend from the top of its flight using the formula:

where d is the distance fallen, g = 9.8 m/s2, and t is the time to fall.

This value can be compared to the actual height of the flight if this is measured. (Whistle must be attached to rocket to time its fall)

2. Add quantitative analysis of the variables. Students can measure the mass of the Alka-Seltzer tablet and the volume of water with a graduated cylinder. Keeping the volume of water constant, these results can be graphed as mass of Alka-Seltzer vs. the time to explode or the time of flight to determine a quantitative correlation of these two variables. Alternatively, do all experiments with one tablet and vary the volume of water. Graph the results similarly. (Requires talking scale for mass and graduated dowel for volume measurement.)

3. Add rocket design elements. Rocket nosecone and fin design can be introduced using overhead sheets or other thin plastic for the material. Overheads can be colored. A basic design template is included, students can then trim this design and assess the results of changes. (Resize image to 1 page, and trace lines and make them tactile using the Sensational Blackboard. The shapes can also be precut and the fold lines made tactile if students do not yet have well-developed cutting skills.)

Image of a seltzer rocket pattern: the fins, nosecone, and body sized to fit around film canister. Cut on solid lines, fold on dotted lines.

Next Generation Science Standards Alignment:

3-PS2-1; 4-PS3-1; 5-PS1-1; 5-PS1-4; MS-PS1-2; MS-PS2-2; 3-5-ETS1-3

Common Core Standards Alignment:

W.3.7; MP.5; 3.MD.A.2; RI.4.3; W.4.7; W.5.7; RST.6-8.3; RST.6-8.7; WHST.6-8.7