Measuring the Density of Solids
Name of Corresponding Unit Plan: Archaeological Documentation
Grade Level: 5-8
Common Core Standards:
RS9-10. 3. Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text.
Math G-MG.2. Apply concepts of density based on area and volume in modeling situations (e.g., persons per square mile, BTUs per cubic foot).
Content Areas: Math, Science
Recommended Length/Duration: 45-60 minute period
Learning Goals: Students will understand the meaning of density and how to calculate its value.
- Discuss how different materials have different qualities. They may be solid, liquid, or gaseous. They may be compact and heavy or expansive and light. One of the measurable characteristics of a material is its density.
- Define density as the relationship between a material’s volume and its mass. A material that is very massive but small, has a high density (e.g. iron, rock, mercury). A material that is less massive for its size would have a low density (e.g. wood, Styrofoam). The standard for density is water because standard metric units derive from water. 1 ml of water = 1 gram, 1l of water = 1 kilogram. Therefore, the density of water is 1/1 g/ml or 1/1 kg/l. We say the density of water = 1. Materials more dense than water will have a value greater than 1. Materials less dense than water will have a fractional value less than 1.
- Describe that to find the density of a material you need to measure its volume and mass. The volume of a regular object can be determined by measuring its dimensions and using the appropriate formula. However, most objects do not have regular shapes, so their volume must be determined by displacement.
- To measure volume by displacement, an object can be submerged in water and measure the amount of water it displaces. Demonstrate how an object submerged will raise the level of the water in a graduated cylinder or measuring cup.
- The mass of an object can be determined by weighing it on a scale.
- Density is calculated by dividing the mass by the volume. Work an example together.
- Organize students into small work groups to find the density of the various objects provided.
- After students have completed their measurements and calculations, compare findings and clarify any disagreements or questions.
Assessments: Check worksheets for accuracy.
Materials/Resources: Density of Solids Worksheets (pdf), Scales, Calculators, Collection of various liquids and granular samples
Special Considerations: Weaker math students might be grouped with stronger students.
Scientific measurements are generally easier to take and calculate in metric than in English units. Additional work may be needed if students are not familiar with metric measurements, or if the teacher chooses to use English units.
Extensions: Students might want to find the density of additional materials at home.
Students might want to find the average density of their body.