Grades 3–5 · Materials & Matter
Which tested pieces can a magnet separate?
A magnet lifts some pieces from a mixture while others stay behind because the materials respond differently to its pull. This selective magnetic force can separate them. A shiny surface or the name metal alone cannot tell which pieces will move.
The supplied observations say that the iron and specified steel samples are attracted strongly enough to be lifted. The aluminum, copper and plastic samples are not observably attracted by this magnet. Steel is a family of alloys, or metal mixtures, so a result for this steel sample does not describe every possible steel.
The pictured mixture contains two iron pieces and three aluminum pieces. Magnetic force moves the two iron pieces toward the magnet and lifts them away from the others. The aluminum pieces remain below. Because the force acts selectively, the mixed group becomes two groups with different locations.
The tested iron squares move toward the magnet, while three aluminum circles remain below. The labels 2 attracted and 3 remain account for every piece in the given five-piece mixture.
In the diagramTested pair: iron + aluminumGiven mixtureAfter magnetNS2 attracted3 remainSquares: tested iron • circles: aluminumAll 5 pieces remain; no new substance.
All five pictured pieces remain after separation, with no new substance made and no iron dissolved into the magnet. Like a sieve using particle size, this process uses a difference in properties. Here magnetic response can separate suitable pieces even when their sizes are similar.
About this explanation
Starting knowledge: Recognize a magnet and count groups while distinguishing a material's name from an observed property.
Sources
- American Chemical Society — Metals and Magnetism