Grades K–2 · Materials & Matter
What happens to these samples after release?
A rubber band grows longer when it is pulled. Let go after a gentle stretch and it springs back. A bent strip of foil often keeps its bend. Both changed shape, but they do different things when the force stops.
In the diagramRubber-band sampleBeforeWhile changedAfter releasePictures show recorded observations.This band returns near its first shape.An adult can read the labels aloud.
While the rubber band is stretched, it pulls back. When the hands stop pulling, that pull brings it near its earlier shape. Springing back is called elastic behavior.
The foil does not spring all the way back. Bending it has made a change that stays. This is why foil can fit around the top of a bowl and keep that shape after a hand lets go.
These different responses make materials useful for different jobs. A rubber band can stretch around a bundle and keep pulling it together. Foil can keep the folds that wrap something up. What happens after a force stops matters as much as what happens while it acts.
About this explanation
The observations describe these samples. Material, size, amount of stretching and earlier damage can change the result.
Starting knowledge: Recognize the same pictured object across before, changed and after views.
Sources
- American Chemical Society — Testing Materials to Learn About Their Properties
- American Chemical Society — The Secret Science of Bounce