Technology and the Diversity of Limits

In this Explore activity, Sails, Propellers, and Fuel, teams of students will test ways of moving boats through the water. After they conduct the tests, the class will decide on the “best” way of moving the boats.

Background Information

Students will be using sails, propellers, and “fuel” to move the boats through the water. The students who are working with the fuel may have their curiosity sparked by this phenomenon. Students will be using the interaction of fizzing antacid tablets with water to produce the gas carbon dioxide. The gas will then move the boat forward. This reaction is similar to the one between baking soda (sodium hydrogen carbonate or sodium bicarbonate) and vinegar (acetic acid). In this reaction, the hydrogen carbonate ion (HCO₃^–) reacts with the acid to make carbon dioxide and water.

Fizzing antacid tablets contain citric acid, sodium hydrogen carbonate, and aspirin. Citric acid is used instead of acetic acid because it is available as a powder and can be mixed with the baking soda to form tablets. When dissolved in water, the citric acid reacts with the hydrogen carbonate ion to release carbon dioxide gas. The aspirin is not part of this reaction. It is included to provide pain relief.

 

Materials

For each class of 30 students, 3 to 4 teams of 3 per protocol:

• a source of water
• 1–10 large tubs or sinks (see Advance Preparation)
• 10 2.5 × 10 × 20 cm wood blocks with a 0.75 mm hole drilled 2.5 cm from one 10 cm side
• 10 sticks of modeling clay
• 10 metric rulers (optional, depending on class decision about criterion)
• 10 stopwatches (optional, depending on class decision about criterion)
• 1 roll of masking tape
• pens or pencils of different colors
• mop and bucket or towels (optional)
• 10 pairs of scissors
• 12 sheets of 8½ × 11 in. white, unlined paper
• 4 craft sticks or new, sharpened pencils
• 7 rubber bands
• 8 paper clips
• 4 plastic beads
• 12 pushpins
• 4 copies of Master 3-4, Propellers (see Advance Preparation)
• 4 aluminum foil pie plates or baking pans
• strips of electrical tape (see Advance Preparation)
• 12 pairs of safety goggles
• 4 10 in. round balloons
• fizzing antacid tablets (see Advance Preparation)
• 4 flexible straws
• 4 250 mL squeeze bottles
• 12 copies of Master 3-1, Protocol for the Sail Test 
• 12 copies of Master 3-2, Protocol for the Propeller Test 
• 12 copies of Master 3-3, Protocol for the Fuel Test 

 

Advance Preparation

The materials list for this activity is long, so begin preparations well in advance. Fizzing antacid tablets are available in bulk at warehouse stores. These stores might be a good option for obtaining the tablets if you have several classes. You will also need fizzing antacid tablets for the Evaluate activity, so you may wish to purchase a large quantity.

Make copies of the four masters that are used in this activity. Four copies of Master 3-4, Propellers, should be sufficient. But, to prepare for 3 to 4 teams per protocol, you will need 12 copies of each of the protocol handouts: Master 3-1, Protocol for the Sail Test; Master 3-2, Protocol for the Propeller Test; and Master 3-3, Protocol for the Fuel Test.

Decide in advance how you will group students. Students will be working in teams of 3 to complete the tests. Each team will test only one way to move the boat forward, and the class will combine the data at the end. This means that for a class of 30, you will have 3 to 4 teams testing each way to move the boat.

Also decide where you will conduct the tests. Large tubs or sinks will work for testing the boats. Small classroom sinks are not sufficient, as they do not allow enough space for the boats to move. You can choose the number of tubs you will use based on what you have available. There are different options, including one tub for the whole class, one for each method of moving the boats (for a total of three), one for every 2 teams of students, or one for each team of students. Decide on the way that works best for you. One good option is to use children’s wading pools if you or other teachers have them available and you have enough space for them.

Stopwatches and metric rulers are listed as optional because, in Step 1, students will decide whether they want to measure the “best” boat based on speed or on distance. If they choose speed, a distance will need to be marked off, and then they will need stopwatches to determine how quickly each boat travels that distance. If they choose distance, then they will need metric rulers to measure how far each boat travels.

You may want to precut strips of electrical tape for students who carry out the propeller test. This will save time during the actual activity. You may also want to precut the paper propellers from Master 3-4, Propellers, to save time.

Create the class chart that you will use in Step 6. You may do this on chart paper, the chalkboard, or an interactive whiteboard. The specifics of the chart will depend on what criterion students choose as their measure of the best boat. If they choose to measure the distance the boat travels, the chart should have a place for them to record the method of moving the boat, the distance traveled, and the “conditions” they used. If they choose to measure the speed of the boat, the chart should have a place for them to record the method of moving the boat, the amount of time it took for the boat to travel the intended distance, and the “conditions” they used. The conditions may include the size and shape of the sail, the number of rubber band twists, or the number of antacid tablets, depending on which method is being used to move the boat.

Finally, make sure you build at least one boat yourself for each of the 3 protocols so that you know how the tests should be set up and can anticipate where your students might have difficulties.

 

Cautions

This investigation involves large amounts of water that could spill and result in a dangerously slippery floor. Ask the students to be careful not to spill the water and to wipe up any spills immediately. You may want to have a mop or towels available.

In the propeller test, students drive pushpins into a block of wood. They then stretch a rubber band from one pushpin to the opposite side of the board. If the pushpins are not driven completely into the board, they could “pop” out and become dangerous projectiles. For this reason, be sure that the students performing the test wear safety goggles.

Caution the students against playing with the paper clips and rubber bands. These items can cause injury.

The blades of the aluminum foil propellers have sharp edges. Tell students to handle the aluminum foil propellers carefully.

Fizzing antacid tablets contain aspirin. Students should not ingest them.

Outcomes and Indicators of Success

By the end of this activity, students will

1. explore methods of boat propulsion.

   They will explore methods of propulsion by

   • building a model of a boat with one type of propulsion
   • listening to and participating in discussions about other teams’ methods of propulsion
   • propelling a boat model through the water using their method of propulsion.

2. expand their ideas about testing.

   They will show their understanding by

   • carrying out a test according to a protocol
   • recording the results of the test
   • comparing the test to building a real boat
   • considering how to improve the test.

3. use evidence to make decisions.

   They will show their understanding by

   • contributing data to a class set
   • coming to a consensus with the rest of the class on the best way to move the boats.

Getting Started

Remind students to read the key idea and linking question in the chapter organizer before starting this activity. Remember that the linking question leading to this activity should be answered by this activity, rather than by students before they have begun the activity. Have students examine the boats in figure 3-3 and describe how each boat moves through the water.

1. Hold a class discussion to decide on the criterion that describes the purpose of the boat. In other words, will the class evaluate the “best” boat based on how far it travels or how fast it travels? The hint may help students understand what they are supposed to do in this step. Have students think about how they will measure the boats to determine the best according to the criterion. If they decide to test how fast the boats move, you will need to set a particular distance for the boats to travel. They will then need to use stopwatches to determine how long it takes the boats to travel that distance. If they determine that the best boat is the one that travels the farthest, then they will need to use a metric ruler to determine the distance the boats traveled. Everyone in the class must agree on the one criterion of whether the best boat moves the farthest or the fastest before moving on to the next step.

2. In Step 2, students decide which method for moving the boats their teams will test. Each team will test either sails, propellers, or fuel. You can allow students to choose, have them draw numbers, or assign them a method.

3. Students should receive the master for the test they will be doing (Master 3-1, Protocol for the Sail Test; Master 3-2, Protocol for the Propeller Test; or Master 3-3, Protocol for the Fuel Test). Give them time to read the protocol. Have them discuss any questions with their teammates. The handouts are the protocols for each method. You will be provided with additional information about the steps of each protocol after Step 7 of this section.

4. Students should send one team member to collect the materials for the team’s test. Make sure students understand that even though there are a lot of materials, not every team will use all of them. Students should be familiar with the materials they will need before they retrieve them.

5. Give students enough time to complete the protocol. You may want to impose a time limit before starting so that they will have an idea about how to use their time. In this activity, students should simply focus on running tests. They will learn more about fair tests in the Explain activity. For this reason, do not bring up fair tests at this point or instruct students to run a fair test. They will have an opportunity during the Explain activity to explain what they would have changed about the tests to make them fair. Have students read the information in the How to Construct a Data Table which is found in the Hint for Step 5. The teacher version of How to Construct a Data Table can be found at this link.

6. Have students record their results on a class chart. Directions for creating the class chart are in the Advance Preparation section for this activity. You might want to have students record their “best” result to save space, and then have them present their own data tables and describe their work in a brief presentation.

7. Conduct a class discussion about the results. Students should come to a consensus about which method is best for moving the boats. Students likely will need help to understand what it means to come to a consensus. The hint provides some support. Coming to a consensus is a teamwork skill. It is different from voting and involves people working through any differences. Some guidelines that may help are to have students listen to others, value different ideas, and ask questions about those ideas. They should gather information before taking a position and be willing to consider the information others present. In the end, not every student has to completely agree with the final decision, but everyone should be able to “live with” the decision. Note that there is no single, correct answer to the question of how best to move the boats. The point of this step is to have students understand the concept of using evidence to support their ideas and practice the teamwork skill of coming to a consensus. As long as their ideas make sense, accept them. The results for the “best” boat may differ from class to class, depending on how students conducted the tests.

 

Protocol for the Sail Test

1. Students who are completing the sail test should use a piece of paper and a craft stick or pencil to create a sail. They should then attach the sail to the boat using modeling clay. Students should use figures 3-1.1 and 3-1.2 as a guide.
   

3. Students should try to move the boats across the tub or sink. They will need to create a wind. The hint tells them to remember how they created the wind so they can do it the same way in each test. The hint is useful, but do not spend time talking about fair tests at this point. Students will learn about fair tests in the next activity and will then have an opportunity to describe how they would change these tests to make them fair.

4. Step 3 showed students what they would be doing in the tests. In Step 4, the teams should decide how to change the tests. It is easier for students to change the tests once they have seen how the boat works and moves. For this reason, be sure they complete Step 3 before you have them think about what to change in the tests. They may need to be reminded of the goal of having the boat go either the farthest or the fastest. Do not emphasize fair tests at this point, as they will learn more about fair tests in the next activity. They may have trouble deciding what to change in the tests. If they seem to be having difficulties, you can suggest changing the shape or the size of the sail. They should not conduct the tests at this point. They are directed to do so in Step 6.

5. Students should create a data table for the tests. Depending on their experience with data tables, they may need guidance about what information to include. For the sail test, they should record the size of the sail, the shape of the sail, and the distance or speed the boat traveled. You might want to approve their data tables before you allow them to continue.

6. Once students have a data table prepared, they should run the additional tests. Remind them frequently that they should record the data for each test.

7. Students should use a pen or pencil of a different color to draw a star next to the conditions that worked best for the boats. The starred items will be the results they share on the class data chart.

8. Have students clean up the materials before moving on to the class discussion. This will ensure that they do not continue to play with them as you discuss the results of the tests.

 

Protocol for the Propeller Test

1. Have students use figure 3-2.1 to guide them on the placement of the pushpins in the blocks of wood. Check that they follow the hint about making sure the pins are pushed down as far as they can go into the block so that they cannot “pop” out and hit someone.

2. Have students examine figure 3-2.2. The paper clips will serve as the base for the propeller. Have students bend one paper clip and insert the bead as shown in Steps a-d.

3. Students should attach a rubber band to a paper clip and squeeze the end of the paper clip so that the rubber band does not come off. You may want to remind them to not play with the rubber bands and paper clips, as they can be a safety hazard.

4. It is very important that students wear safety goggles before continuing the protocol. After this point, the rubber bands or pushpins could become projectiles, so eye protection is needed. Using figure 3-2.3 as a guide, have students continue building the boat.

5. Students should “wind up” the paper clip and hold it in place.

6. Once students release the paper clip, they should make sure that it spins easily. It should not make any contact with the wood. Students should continue adjusting the paper clip until it spins easily.

7. Students should unbend another paper clip, but they should follow only Step 2a in figure 3-2.2. They should not continue unbending it as directed in Steps 2b–d.

8. Using figure 3-2.4 as a guide, students should use a strip or two of electrical tape to hold the two paper clips together. As mentioned in the Advance Preparation section, you may want to have these strips precut to save time.

9. Students should choose one of the propellers from Master 3-4, Propellers. If you have not already cut out these propellers, students should cut out the one they like. Then they should trace the propeller onto an aluminum foil pie plate or baking pan, and cut out the aluminum foil propeller. Remind them that the edges of the foil can be sharp.

10. Using figure 3-4.5 as a guide, students should attach the aluminum foil propeller to the paper clip with a strip or two of electrical tape. They should bend the propeller so that it does not touch the wood block.

11. Students should test the boat in the water by winding up the propeller and releasing it.

12. Step 11 showed students what they would be doing in the tests. In Step 12, the teams should decide how to change the tests. It is easier for students to change the tests once they have seen how the boat works and moves. For this reason, be sure they complete Step 11 before you have them think about what to change in the tests. They may need to be reminded of the goal of having the boat go either the farthest or the fastest. Do not emphasize fair tests at this point, as they will learn more about fair tests in the next activity. They may have trouble deciding what to change in the tests. If they seem to be having difficulties, have them read the hint, which suggests aspects they might change. They should not conduct the tests at this point. They are directed to do so in Step 14.

13. Students should create a data table for the tests. Depending on their experience with data tables, they may need guidance about what information to include. For the propeller test, they should record the number of rubber band twists and the shape of the propeller. You might want to approve their data tables before you allow them to continue.

14. Once students have a data table prepared, they should run the additional tests. Remind them frequently that they should record the data for each test.

15. Students should use a pen or pencil of a different color to draw a star next to the conditions that worked best for the boats. The starred items will be the results they share on the class data chart.

16. Have students clean up the materials before moving on to the class discussion. This will ensure that they do not continue to play with them as you discuss the results of the tests.

 

Protocol for the Fuel Test

1. Students should blow up the balloon first. This helps loosen the balloon. Caution students against having more than one student put his or her mouth on a given balloon.

2. Students should break an antacid tablet into 4 pieces and put the pieces in the balloon. If the pieces do not fit into the neck of the balloon, they may be broken into smaller pieces. Make sure students do not spend too much time doing this.

3. Have students put the balloon over the end of the flexible straw nearest the joint. They should then carefully wrap tape around the balloon and straw 6 times. Instruct them to make the seal completely airtight, following the information in the hint.

5. One student from the team should inflate the balloon by blowing into the straw. If any air leaks out, the setup will need to be adjusted.

6. Once students have a tight seal on the balloon and straw, they should squeeze the balloon to remove all the air.

7. Students should follow the steps for setting up the boat. Have them refer to figure 3-3.1 to make sure they are setting up the boat in the right way.

8. Students should fill a squeeze bottle with water. They should start Step 9 with a full bottle so that they do not run out of water while filling the balloon. The reaction between the antacid tablet and the water will begin as soon as they start adding water, so it will affect the results if they have to stop halfway through the filling process to retrieve more water. They should not add water to the balloon during Step 8.

9. Once students have taken the boat to the tub of water, they should squeeze water through the straw into the balloon. Have them read the hint and examine the illustration in figure 3-3.2 before they begin. As soon as the balloon is filled with water without inflating it, one student should put a finger over the end of the straw. This will prevent the carbon dioxide gas from escaping.

10. Make sure students understand that they should keep a finger over the end of the straw even while the boat is in the water. Only when the balloon is inflated about halfway should the assigned student move his or finger away from the end of the straw.

11. Step 10 showed students what they would be doing in the tests. In Step 12, the teams should decide how to change the tests. It is easier for students to change the tests once they have seen how the boat works and moves. For this reason, be sure they complete Step 11 before you have them think about what to change in the tests. They may need to be reminded of the goal of having the boat go either the farthest or the fastest. Do not emphasize fair tests at this point, as they will learn more about fair tests in the next activity. They may have trouble deciding what to change in the tests. If they seem to be having difficulties, have them read the hint, which suggests aspects they might change. They should not conduct the tests at this point. They are directed to do so in Step 13.

12. Students should create a data table for the tests. Depending on their experience with data tables, they may need guidance about what information to include. For the fuel test, they should record the number of antacid tablets they used. You might want to approve their data tables before you allow them to continue.

13. Once students have a data table prepared, they should run the additional tests. Remind them frequently that they should record the data for each test.

14. Students should use a pen or pencil of a different color to draw a star next to the conditions that worked best for the boats. The starred items will be the results they share on the class data chart.

15. Have students clean up the materials before moving on to the class discussion. This will ensure that they do not continue to play with them as you discuss the results of the tests.