Students repeatedly reduce the size of a clay ball while placing it in water to investigate the question: Does changing the amount of material in an object change the object’s density?
Objective
Students will be able to explain that the density of a substance has to do with how heavy it is compared to the size of the object. Students will also be able to explain that density is a characteristic property of a substance.
Key Concepts
- Density is a measure of how heavy something is compared to its size.
- If an object is more dense than water it will sink when placed in water, and if it is less dense than water it will float.
- Density is a characteristic property of a substance and doesn’t depend on the amount of substance.
Note: We are purposely using the terms “size” and “amount” instead of “volume” in discussions of density. We are also using “heavy”, “light”, and “weight” instead of “mass”. If your students have already learned the meaning of volume and mass, you can easily use those terms to define density as Density = mass/volume and then use those terms in the lesson.
NGSS Alignment
- NGSS 5-PS1-3: Make observations and measurements to identify materials based on their properties.
Note: The NGSS Structure and Properties of Matter for 5th grade, Performance Expectation 5-PS1-3 states “density is not intended as an identifiable property. Assessment does not include density or distinguishing mass and weight.”
Although the standard does not call for density to be used as a characteristic property to identify a substance, a basic introduction to density is included here as an optional element of a learning progression leading up to a middle school understanding of density.
Summary
- Students are introduced to the concept of density and that density has to do with how heavy something is relative to its size.
- Students are also introduced to the idea that whether a substance sinks or floats in water is a characteristic property of that substance and does not depend on the amount of the substance.
- Students also learn that if an object is more dense than water it will sink when placed in water, and if it is less dense than water it will float.
Evaluation
Download the student activity sheet and distribute one per student when specified in the activity. The activity sheet will serve as the Evaluate component of the 5-E lesson plan.
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