District of Columbia Grade 2 Science

Match a material’s properties to the job it must do

Use invented material-test observations to choose a model cover, explain tradeoffs, and follow a selected DC Grade 2 NGSS reference.

The DC science standards directory identifies NGSS adoption in December 2013 and links the standards publisher. Use the Publisher NGSS document for the selected performance expectations and their examples and boundaries. This activity selects a Grade 2 expectation. It is one part of a science course, not a complete curriculum.

Choose a cover for a small classroom model

A model shelter needs a cover that keeps the space below it dry and survives being bent around its frame. The table gives invented observations from equal-sized samples tested with the same water application and bending routine. Choose a material for this particular job and explain which observations support the choice.

Explain the evidence or model

The plastic sample kept the area below it dry and did not tear during the bending routine. It meets both stated needs in this model. The foil sample also kept the area dry, but it tore when bent. The paper sample became wet underneath and tore. A response should connect the observations to the two criteria, rather than choose plastic because of its color or because someone always uses it. These are results for the described samples, not measurements of every plastic, foil, or paper product.

What to check in the explanation

Keeping water out is only one of the two requirements. Choosing foil without mentioning its tear overlooks the bending constraint. Calling paper “bad” also goes too far: absorbent paper might be useful for wiping a spill. A material’s suitability depends on the task. The table does not give price, environmental impact, or strength under a heavy load, so those cannot be added as findings from this comparison.

Plan the next activity

1. Name the two needs before reading the observations.
2. Compare each sample with each need, including any tradeoff.
3. Explain the choice with the observations and identify something the comparison did not test.

With adult guidance, compare suitable classroom samples on a tray using one consistent routine. Record qualitative observations such as wet or dry and torn or intact. Keep sample size, water application, and bending consistent; a larger sample or a gentler bend would make the comparison less useful. Let the actual observations replace the invented table. Then change the purpose to absorbing a spill and reconsider which evidence matters. Do not use this small model as a recommendation for a real building roof.