How do all the underwater vehicles in the graphic novel float, sink and resurface?
Lesson One Overview:
Students learn about the relationship between buoyancy, density, and mass through hands on experimentation. They measure various objects in calculating the density of each one. After measuring they record and graph the information. The goal is to have them understand how the mass, volume and density affect the buoyancy of an object. Through this activity, they learn how the undersea vehicles in the graphic novel are able to operate.
Classroom Lab :
In cooperative learning groups of 4, have students predict the mass of the 10 different objects. Have the group assign one person to record predictions. If Noteshare is available to the students, have them create a Notebook specifically for this Lab. If not, choose a program for recording results. They should also sketch the materials and procedure as they take lab notes.
1. Mass - Have the students determine the real mass by passing the object (s) around the group having each student measure the object. Students should then look at the data and discuss any discrepancies between predictions and actual data. Inevitably, they will discover that the size of an object does not determine the mass.
2. Volume - Students then predict the volume of 10 different objects. For this activity students observe 3 different methods to determine the volume. One is the formula method where they apply length x width x height (to be used with their regular shaped objects and the overflow method to be used with irregular shaped objects. The next method for calculating is capacity or how much the object will hold. Have them use the same procedure as determining mass, recording all results in the Notebook.
3. Density - Students use a triple beam balance and a metric ruler to determine the density of objects. The dishpan for overflow will also be used. The objects available should include those that will sink and those that will float. The discussion here should focus on how the density changes according to the volume or mass of each object. Using the mass per unit volume or one gram per cubic centimeter, students should see the relationship to density.
4. Floating objects and sinking objects from the previous activity now should be examined to find out exactly why. Looking at the data that they have collected on density, students should be able to see that the relationship of mass to volume determines the ability of these objects to float or to sink.
5. How do submarines such as the one designed by Capt'n Eli, dive into the water and resurface? Using this simple procedure, students answer this question.
- Begin by filling a glass with water and put a medicine dropper in it. With the dropper, suck enough water in so that it floats with just a little bit of the rubber part bobbing out of the water. This becomes the "diver" and the term for this is "neutral buoyancy" meaning that the water it displaces is the same as the diver. The diver stays in one spot because the displaced water pushes up on the diver with the same amount of force that the diver itself pushes down on the water thus the diver remains in one spot and does not float up or sink down (neutral).
- Now that the dropper is ready, fill a plastic quart soda bottle to the top leaving no space between water and cap. Lower medicine dropper into bottle and screw on the cap tightly.
- Squeeze the bottle thus increasing pressure and what do you observe? (They should see that as pressure is increased, the water in the dropper increases causing it to sink) Students should experiment applying varying amounts of pressure to make the dropper hover in the middle of the bottle.
- How does this experiment answer the question regarding submarines? Have students research how submarines operate in a similar fashion. They will discover that submersibles have ballast tanks that fill up with water to make them dive and when it is time to resurface, air is pumped into the tanks forcing water out and allowing it to float.
Capt'n Eli is operating his submarine in the ocean rather than in fresh water. How can you repeat the diver experiment to simulate these conditions. What do you predict will happen? Record your results.
(Students will find that salt water is denser than fresh water)