Now consider a smooth gray lump that Hollis has brought from home.

Here is a table of five known materials: steel, aluminum, oak wood, wax and stone.

The table of five known materials and three of their properties.

A magnet does not pull the lump. Steel is the only one a magnet pulls, so Hollis crosses steel out.

After the magnet test: steel is crossed out.

The lump sinks in water. Oak wood and wax float, so he crosses them out.

After the water test: oak wood and wax are crossed out too.

The lump is shiny like metal. Stone is not shiny like metal, so he crosses stone out.

After the third test: one material is left.

One material is left: aluminum. The lump is aluminum.