Grades 5-9
32 activities – 192 pages

Density is one of the concepts not readily understood by students because it is usually introduced to them in the form of a mathematical formula: density = mass/volume. While this formula accurately describes how to calculate density, it doesn’t necessarily help students understand the concept of density. Students need to start at the concrete level in order to understand density at the abstract level.

Floaters and Sinkers builds the concepts of mass and volume first, and then has students look at the relationship between the two. They will compare the masses of different objects with equal volumes, and the volumes of different objects with equal masses. Density will then be explored. Students will find the density of water (which is one) and then the densities of different objects. They will discover that objects with densities greater than one will sink in water, while those with densities less than one will float.

Students will discover other applications of density. They will find the densities of different types of wood, and from their calculations, they will be able to determine the float lines of the pieces. They will find the level of the waterline on the hull of a loaded cargo ship, design boats from clay that will carry the most cargo, find the densities of different liquids and form a flotation column, and change the density of water by adding salt.

Teachers will also appreciate the integration of measurement skills utilized within activities, including a review of measuring mass and volume by formula and water displacement.

Floaters and Sinkers will make the concept of density more real to students and they should have fewer difficulties doing density problems and applying density formulas. Why do rocks sink and boats float? Your students will be able to tell you!