# Density

Density is a property of materials included in the National Science Education Standards Physical Science Content Standard B. It is a property by which mixtures can be separated but has much more profound applications outside the classroom such as rock formation, severe weather and living systems. But none of these concepts are fully comprehensible without a fundamental conceptual understanding of density. This is an abstract concept combining the concepts of mass and volume. The resources here provide examples designed to help you facilitate student acquisition of a conceptual understanding of density.

Funny Water
This page from the National Science Education Standards starts the story of a middle school teacher’s inquiry lesson on density.

Density Balloon
What happens to the density of a balloon as it is heated and cooled? Here students use a hair dryer to heat a helium-filled Mylar balloon, causing it to rise, and let it cool, causing it to drop. The activity includes a description, a list of science process skills and complex reasoning strategies being used. Also provided are content topics, a list of necessary supplies, instructions, and presentation techniques. The content of the activity is explained, and assessment suggestions are provided.

Liquid Rainbow
In this density activity, students determine the relative densities of five liquids and layer them atop one another in a straw.

Atmospheric Properties: Convection

Potato Float
How can a potato wedge be made to hover in the center of a glass of liquid? Students investigate density using potato wedges and water and sugar water solutions.

# Waves

The National Science Education Standards (NSES) tell us that students in grades 5-8 should “begin to see the connections among . . . [energy forms] and to become familiar with the idea that energy is an important property of substances and that most change involves energy transfer.” Yet there is no explicit direction to introduce students to waves in the context of energy. But what better way to help students connect the mechanical energy of visible ocean waves to the “work” they can do in moving objects all the while transferring energy from kinetic to potential and back? Resources provided here will help you help your students begin to conceptualize waves and their relationship to energy.

Waves and Wave Motion: Describing Waves
This module introduces the history of wave theories, basic descriptions of waves and wave motion, and the concepts of wave speed and frequency.

Seismic Waves
How can P and S waves predict the inner structure of the Earth? Students activate four seismographs that send out P and S waves and watch as the waves are reflected and refracted while moving through the Earth and are asked a series of questions about the waves and interior of the Earth. From the results and provided information, students see how the movement of P and S waves predicts structure within the Earth.

Sound
This site, created by and for 5th grade science students and educators, explores, illustrates, and explains the science of sound and music, including compression waves.

Waves, Sound and Light
These online applets or “gizmos” cover prisms, refraction, and ray tracings with lenses and mirrors. Each gizmo allows users to manipulate variables such as wave length or angle of reflection and each is accompanied by an illustrated, printable guide. The Explore Learning site requires a subscription but does offer a 30-day free trial and five minutes of free access each month for each of the applets.

# Distance-Rate-Time

Measurement is one of the core NCTM Principals and Standards for School Mathematics content standards, and rate is central to its practical application. While most middle school students know the distance-rate-time formula, they may still benefit from a closer study of the relationship.

Understanding Distance, Speed, and Time Relationships
Students see two runners move along a track. As they change the speeds and starting points of the runners, they watch the race but also examine a graph of the time-versus-distance relationship. Excellent questions guide the class as they investigate the scenario from several angles.