• transparent block with silver rectangular weights inside submerged under water
  • transparent block with silver rectangular weights floating on the surface of the water in a shoe box sized container
  • transparent block with silver rectangular weights inside partially submerged under the water

Whatever Floats Your Boat


The context of a boat floating is used to launch the investigation into why objects sink and float. Archimedes Blocks are used to investigate the relationship between density and floating and sinking. As the students change the mass of the Archimedes Blocks, they use their knowledge of fractions to calculate the density and make connections to their observations of how far the block is submerged.

Example Handout

  • Grades 4-8
  • In person only.
  • Requires basic skill with division and simple fractions.
  • Access to a water supply is required.


  • Archimedes Blocks and weights

  • Container to hold water (preferably shoe box size) 

Follow Up and Resources

This can be an effective launch point to dig deeper into density. Check out the following: 


Number and Operations - Fractions

  • MAFS.3.NF.1.3: Explain equivalence of fractions in special cases, and compare fractions by reasoning about their size.
  • MAFS.4.NF.1.1: Explain why a fraction a/b is equivalent to a fraction (n x a)/(n x b) by using visual fraction models, with attention to how the number and size of the parts differ even though the two fractions themselves are the same size. Use this principle to recognize and generate equivalent fractions.
  • MAFS.4.NF.1.2: Compare two fractions with different numerators and different denominators, e.g., by creating common denominators or numerators, or by comparing to a benchmark fraction such as 1/2. Recognize that comparisons are valid only when the two fractions refer to the same whole. Record the results of comparisons with symbols >, =, or <, and justify the conclusions, e.g., by using a visual fraction model.
  • MAFS.6.RP.1.1: Understand the concept of a ratio and use ratio language to describe a ratio relationship between two quantities.
  • MAFS.6.RP.1.3: Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations.

Properties of Matter

  • SC.3.P.8.2: Measure and compare the mass and volume of solids and liquids. 
  • SC.4.P.8.1: Measure and compare objects and materials based on their physical properties including: mass, shape, volume, color, hardness, texture, odor, taste, attraction to magnets. 
  • SC.5.P.8.1: Compare and contrast the basic properties of solids, liquids, and gases, such as mass, volume, color, texture, and temperature. 
  • SC.8.P.8.3: Explore and describe the densities of various materials through measurement of their masses and volumes. 
  • SC.8.P.8.4: Classify and compare substances on the basis of characteristic physical properties that can be demonstrated or measured; for example, density, thermal or electrical conductivity, solubility, magnetic properties, melting and boiling points, and know that these properties are independent of the amount of the sample. 

The Practice of Science 

  • SC.3.N.1.3: Keep records as appropriate, such as pictorial, written, or simple charts and graphs, of investigations conducted.
  • SC.6.N.1.1/SC.7.N.1.1/SC.8.N.1.1: Define a problem from the sixth/seventh/eighth grade curriculum, use appropriate reference materials to support scientific understanding, plan and carry out scientific investigation of various types, such as systematic observations or experiments, identify variables, collect and organize data, interpret data in charts, tables, and graphics, analyze information, make predictions, and defend conclusions.