The Boat and the Beetle

Build Materials (For each team)

Required Materials

• Modeling clay/plasticine
• Scale to break modeling clay into pieces
• Toy boats/ships
• Crayons and coloring sheets with boat theme

Testing Materials

• Inflatable play pool/tank or large bowl of water
• Plastic table covering

Materials

• Inflatable play pool/tank or large bowl of water
• Plastic table covering 

Process

As students are sculpting their boats, allow them to test how well their design floats. They can then change (redesign) their boat and test again until they have a design that floats.

Design Challenge

You are an engineer given the task of building a boat out of modeling clay. Draw a picture of your planned design, sculpt your boat, test it by floating it on the water. If it sinks, change (redesign) your boat and test it again until your boat floats. 

Criteria 

• Draw a picture of the design
• Sculpt the boat from modeling clay

Constraints

• You can only use the modeling clay to build your boat

Review and share the topics on the Teacher Resource sheet. Review the topics in the Background Concepts Section. The following short story can be used as a starter to engage students in the hands-on activity.

Once upon a time there was a beetle who loved to tell everyone how fast he could run. “I am the fastest insect in the park,” he would say. His slow and steady friend the snail, tired of hearing him brag, challenged him to a race. “Ha,” the beetle thought to himself, “there is no way a snail could ever win against me.”

On the day of the race, all of the insects in the park gathered to watch. The centipede waved a checkered flag to start the race. The beetle zoomed past the starting line as fast as he could, while the snail carefully inched herself forward bit by bit. The beetle cried out “You will never win this race at that slow, slow pace.”

Out of breath from running, the beetle eventually reached a small pond of water. He thought, “I have plenty of time. I just will go around the pond.” The beetle sped off on his way.

Inch by inch the snail crawled along the path. As she reached the pond, she thought, “It would be much shorter if I could somehow float across the water.” Perhaps I could build a boat. 

The snail gathered up some leaves, twigs and vine. She fashioned a small boat that helped her glide smoothly across the water of the pond. When she got to the other side, she hopped off the boat and could see all of her friends waiting for her at the finish line.

Little by little the snail crept along the path until she crossed the finish line at long last. All of her friends cheered. “Hooray for snail!” they cried. A moment later the beetle came running across the finish line. “I can’t believe you beat me!” he said. “You know,” the snail replied with a smile, “being the fastest isn’t always everything”. “Sometimes if you just slow down for a moment and think about your challenge, you can come up with great solutions.”

1. Break the class into 2-3 smaller groups. 
2. Set up your classroom so that Group 1 has access to the water and modeling clay. Group 2 will draw and color their planned designs.You can choose to have a 3rd Group that can engage in play activities with toy boats/ships or color on sheets with a water theme (color the sail on a sailboat).
3. Next, set up the work space with a pool or tank of water and a plastic table covering to protect surfaces from spills.
4. Prepare several even lumps of the modeling clay at the same size and weight but leave some unprepared clay.Explain to the students why the lumps of clay are the same so it is a ‘fair test’ for all students.
5. Give each student a piece of modeling clay to sculpt their boats. You may want to keep the students in 2-3 small groups as they sculpt to allow for better supervision.
6. Ask the students to first think about what their boat will look like. They should draw a picture of their planned design.
7. After they have drawn their planned design, students should sculpt their boat. As they create their boats, give them access to the water pool to test how well their boat is floating. Each time they test, they can make changes (redesign) to their boat to help it float better.
8. As the students are planning and sculpting their boats, use vocabulary words as you interact with them:
   Float – to rest on top of a water (or a liquid)
   Sink – to go down below the surface of water
   Hull – the main part of a ship or boat: the deck, sides, and bottom of a ship or boat
   Displace – when a floating object physically pushes water out of the way
   Displacement – the volume or weight of water displaced by a floating body (as a ship) of equal weight
   Buoyancy – the ability of an object to float on water
9. Once the students have successfully sculpted a boat which floats, have a class discussion and talk about the reflection questions below.

Optional Extension Activity

Have the students add weight to their boat (small toys, coins, items that weigh about the same amount) to pretend there is a snail in their boat. Again, have the students test and make changes (redesign) their boats based on the results.

Student Reflection

1. Did your boat sink or float? If it did not float, how did you change it so it displaced more water?
2. How many times did you have to test and sculpt your boat again before it would float?
3. Did you have to change the shape of your boat’s hull?
4. What did you like about other students’ boats?
5. Have you learned with buoyancy means?

The lesson can be done in as little as 1 class period for older students. However, to help students from feeling rushed and to ensure student success (especially for younger students), split the lesson into two periods giving students more time to brainstorm, test ideas and finalize their design. Conduct the testing and debrief in the next class period.

Common Misconceptions

Surface tension – some children will be familiar with bugs which can ‘skate’ across the surface of water, using its surface tension and will give this explanation for why a boat can float. They may have seen a paper clip ‘floating’ (actually it is balancing, not floating) on the meniscus of water. Again, this is surface tension. 

No object with holes in it can float – some children will think that because the hull of their boats cannot remain floating with gaps in them, then this will always be the case.

Light things float, heavy things sink -If you have allowed the children to play in water before, (I hope so!!!) they will already be familiar with the principles of floating and sinking and will have some prior knowledge. This means that they will have some ideas which they might over generalize  and you need to gently correct them.

Metal is too heavy to float – because we often allow children to experiment with materials in a small way (before asking them to generalize their ideas, they may present misconceptions such as these). This is linked with the above misconception.

Surface tension is a really special scientific principle – well done for knowing about this, it is very interesting! However, in the case of this activity,  we break the links between the water molecules with the hull of the boat. So the tension is lost and the boat would sink suddenly…like the paper clip or bug would, if the tension were broken by a drop of soap or a big wave.

Correcting explanations 

No object with holes in it can float – in the case of a boat, like you have made, this is true. We saw that this is because of displacement. In a boat with a hole in it the water isn’t being moved out of the way, it leaks back in and fills up the hull and the boat sinks. (Show them this with your own model boat. Punch a reasonable hole in it so that it works quickly.) 

BUT, some objects do have holes in them and they still float. Objects like pumice stone, sponges, and wood. This is because they have pockets of trapped air inside them. This makes the object much lighter than the water and so they still float at the top (because of buoyancy). Some things (e.g. a sponge) will fill those air pockets with water and will gradually sink, but others, like wood will not. This is why lots of people make rowboats and canoes out of wood, it is very buoyant. 

Light things float, heavy things sink – This is a really good observation, because it is generally true.  Ask the children to think of some examples where this is right – e.g. corks, rubber duck, toy boats vs. rocks, solid objects like a fork or key.  But, because of buoyancy and displacement, we can make heavy things float, if we design and shape them in the way you did in this activity. Can children talk about a ferry boat or other large heavy object they have seen or experienced riding on? If not you may tell them a story from your own experience of a cruise ship or other boat ride. 

Metal is too heavy to float – use the above explanation, you may want to supplement this with pictures of large metal ships at sea, such as tankers, aircraft carriers, etc.

• Hull: the main part of a ship or boat: the deck, sides, and bottom of a ship or boat
• Buoyancy: the ability of an object to float on water
• Constraints: Limitations with material, time, size of team, etc.
• Criteria: Conditions that the design must satisfy like its overall size, etc.
• Displace – when a floating object physically pushes water out of the way
• Displacement – the volume or weight of water displaced by a floating body (as a ship) of equal weight
• Float: to rest on top of a water (or a liquid)
• Engineers: Inventors and problem-solvers of the world. Twenty-five major specialties are recognized in engineering (see infographic).
• Engineering Design Process: Process engineers use to solve problems. 
• Engineering Habits of Mind (EHM): Six unique ways that engineers think.
• Iteration: Test & redesign is one iteration. Repeat (multiple iterations).
• Prototype: A working model of the solution to be tested.
• Sink: to go down below the surface of water
• Surface tension: An effect where the surface of a liquid is strong.
  

Writing Activity