I used this lesson as part as a middle school physical science class. The curriculum STC/MS Properties of Matter provided the main structure for the class. This particular lesson is not part of the curriculum; it’s an addition that I wrote because I felt that the density unit would benefit from the presence of a capstone activity. I particularly like this lesson because it is rigorous (students need to calculate the densities of several complex objects) while being tremendously fun. It is also a good interim assessment which allowed me to identify any students who needed extra help understanding density well before they were tested on it.
Many teachers would need to teach this over several class periods, but because this class met for unusually long sessions, we were able to do the entire lesson in one day.
•Check homework – randomly call on students to answer the questions from “Air Heads” in the Properties of Matter student guide.
• Do Now: Why does a boat made of steel float?
Boat Building Challenge
• Define challenge:
a. Build a boat that will hold the heaviest load possible;
b. Predict what the density of the boat will be when empty and with the load that sinks it;
c. Measure and calculate the density of the boat both empty and with load that sinks it.
• Distribute supplies- one 20cm x 20cm square of aluminum foil, two drinking straws, one piece of computer paper, 40cm of tape, stapler (shared), scissors (shared).
• Allow time to build boats, make density predictions, and measure/calculate the density of the empty boat.
• As a class, float boats in water-filled tub and add coins until each boat sinks. Find mass of the coins that sunk the boat. Calculate the density of the boat as it sank.
• Class discussion: How did you predict the density of your boat before and after sinking? Were your predictions accurate? If not, what could you have considered to improve them? If you were going to make a second boat with the same materials, what would you do differently?
Demonstration: Introduction to Temperature and Density
• Show ball and ring set up. (When cool, the ball just passes through the metal ring. When heated, the ball is unable to do so.)
• Give students time to make a chart to record predictions and observations. Have a confident student share his/her chart with the class and discuss it to make sure that the charts include all the necessary parts. Record predictions.
• Heat ball and ring. Record observations.
• Class discussion: What happened to the volume of the apparatus? The density? What is your evidence?
• Write a procedure for a thought experiment: How could you measure the density of your own body using materials that you actually have access to?
Properties of Matter: Student Guide and Source Book. Burlington, NC: Carolina Biological Supply, 2000. Print.