How do pencils make marks?
For grown-ups: the science
A pencil rubs tiny pieces of graphite onto the paper, making a mark.
Pencil cores are typically a mixture of graphite, clay, and binders, not pure graphite. Abrasion transfers graphite-rich particles to the rough fiber surface of paper; greater pressure generally increases deposition and darkens the line.
What about...?
Ask your child's own question
Transcript
Look at a pencil sliding across white paper. How does it leave a gray line behind?
Inside the pencil is a dark stick made mostly of graphite, a soft kind of carbon. It rubs off when the tip moves on paper.
Paper has lots of tiny bumps and spaces. Those bumps scrape off teeny pieces of graphite and hold them.
More rubbing leaves more graphite on the paper. That is why pressing harder can make a darker mark.
So, a pencil makes marks by leaving graphite on paper. Erasers can lift much of that graphite away!