Skip to content
KinPilot™Learn & Explore
Menu
← TopicsReading path →

Grades K–2 · Everyday Life

How does a pencil leave a dark line?

A pencil has a dark tip inside its wooden cover. The dark material is called graphite. In an ordinary pencil, graphite is mixed with clay. The wood holds the tip so it can make a small, neat mark.

J68 visual explanation6 graphite symbols are on paper and 6 remain in the tip, totaling twelve. These supplied symbols illustrate material transfer, not a measured wear rate.A pencil leaves some of its dark tip behindEnlarged contact · little dark marks stand for graphitePencil + paperA solid tip wears downClose viewGraphite stays on paperPaper rubs the tip; the dark material moves onto the page.

In the diagramA pencil leaves some of its dark tip behindEnlarged contact · little dark marks stand for graphitePencil + paperA solid tip wears downClose viewGraphite stays on paperPaper rubs the tip; the dark material moves onto the page.

The close view follows graphite from the pencil tip onto the bumpy paper surface.

Paper feels smooth to a finger, but up close its surface has tiny bumps and fibers. As a pencil moves across it, the paper rubs the tip. Little pieces of graphite come off and stay on the page.

Those dark pieces make the line we see. The pencil has given some of its tip to the paper. Many marks slowly wear the tip down. The line is solid material left behind, so the pencil can write without liquid ink.

About this explanation

Starting knowledge: Recognize a pencil, its tip and a sheet of paper.

Sources

  • American Chemical Society — The Secret Science of Pencils & Erasers
  • ACS Omega · Kim and colleagues — Graphite pencil electrodes formed on paper by frictional sliding
← Grades K–2 topics