Summer Research Program for Science Teachers


Carla Brathwaite

Midwood High School

Brooklyn, NY

August 2004


What Floats Your Boat?



Unit – Measurement


Objectives:  Students will be able to calculate the density of an irregular solid and a rectangular solid.


Materials:  Wood blocks, scales, 12 inch rulers (with cm), overflow cups, basins for water, 50 ml graduated cylinders, marbles, clay blocks, paper towel, a medium size rock (not brick)


Do now:  What is density?  How do we find the density of an object?


Motivation:  You go to the doctor and they take 2-3 tubes of blood.  What do they do with these tubes of blood?  (eventually get to centrifuge), What does this do?  (denser particles settle first), What do they do next? 



1.       – Go over the class’ definition of density as well as the different methods the class brings up about finding the density of the object.

2.      Distribute wood blocks and allow class to find the density (prompt if necessary)

3.      Create a chart on the board and calculate the class average (go over how this is done)

4.      Hold up a rock – ask the class how you’d find the density of the rock

5.      Have 2 -3 pairs of students find the density of their marble, compare densities

6.      Ask the class if we were to cut the marble or the blocks in ½ would the density change?  Why or why not

7.      Distribute a clay block to each pair of students, have them use both methods to find the density of the block.

8.      Get a class average for each method

9.      Discuss why we used cm instead of inches, which method is more accurate and why, as well as introduce the concept of sig. figures

10.  May have 5-10 min left – extra credit to the first 3 pairs of students to build a boat (only using their clay) that floats in their pitcher of water.  Remind them to think of the different types/shapes of boats.

11.  End with the concept that an object will sink until it displaces an amount of water equal to its own weight


Summary:  Have students explain the three things they learned about density today (maybe 1 or 2 students out loud).



Homework – Bring in a picture of 3 different types of boats.  Explain how their shape can indicate the type of load/function they were created for.  (internet activity)


Standards Addressed:

S4b – Demonstrates an understanding of the designed world

S4c – Demonstrates an understanding of health

S4e – Demonstrates an understanding of the impact of science

S5e – Works individually and in teams to collect and share information and ideas




Idea for this lesson came from a CPO workshop with the same title as the aim.  The entire workshop presentation is available:


Return to General Science Lesson Plan Menu