The Two Gray Bars
Ana finds two gray bars in her uncle's workshop, the same size and just as shiny. One is aluminum and one is steel.
How can Ana tell which is which?
Page 1
Science · Grade 5 Science
Chapter 1: Matter and Its Properties
What it is made of, not what it looks like.
Ana finds two gray bars in her uncle's workshop, the same size and just as shiny. One is aluminum and one is steel.
How can Ana tell which is which?
Make your guess to turn the page.
Still to come: 9 pages · Words to Know · What We Learned · 4 questions · Explain It in Writing · Ask and Wonder
The idea this lesson is working on — Children judge a material by its look: gray and shiny means "metal", and the darker one must be the heavier kind. The story has two bars that look alike, and Sam's guess from looking happens to be right, which makes the point sharper: a right answer from a bad reason is still a guess. Ask: which tests told the bars apart, and which did not? A property is something anyone can test and get the same answer.
Use more than one property — Several materials share any one property. The mystery block shows the narrowing: four possible, then three, two, one. A test only narrows the list when the materials left on it answer that test differently, which is why the order of tests matters less than their number.
A note on steel and shine — Ordinary steel is magnetic; some stainless steels are not, so "steel sticks to a magnet" is a rule for the common kind. Shine (reflectivity) is itself a property scientists use, but it cannot separate aluminum from steel, which is why the book treats "shiny and gray" as only how these two bars look.