ACS: The Secret Science of Stuff - The Secret Science of Pencils & Erasers

What does the number on the pencil mean?

The pencil “lead” is actually a mixture of graphite and clay. More clay in the mixture makes the lead harder. A harder lead has a higher number. Pencils are numbered from 1-3 but most people use a number 2. Harder lead makes a lighter mark and softer lead makes a darker mark.

How long does a pencil last?

It’s been estimated that the average pencil has enough graphite to write about 45,000 words!

What if you made a mistake before they invented erasers?

Before using rubber for erasing, people used to use bread!


Science Topics
Kindergarten, 1st Grade, 2nd Grade, 3rd Grade, 4th Grade, 5th Grade
Descriptions of PDFs

Print this page

What are you looking for?


ACS (American Chemical Society)

Website URL

Type of Resource

Online Interactive Activity
PDF File

Assigned Categories