How do we know atoms exist when we cannot see them with our eyes?

This free FranklyChemistry classroom poster introduces students to the evidence for the existence of atoms and encourages them to think about an important scientific question: how do we know?

The poster highlights several strands of evidence, including:

observations of the predictable behaviour of matter
simple whole-number ratios in chemical reactions
diffusion and Brownian motion as evidence for particles
the development of experimental evidence from Dalton to modern atomic science

It is designed as a visual aid/display resource for chemistry classrooms and as a starting point for discussion about how scientific models become supported by experimental evidence.

Watch the accompanying FranklyChemistry video

The poster accompanies my video:

How Do We Know Atoms Exist? | The Evidence for Atoms

Watch the video on YouTube

The video develops the ideas behind the poster and explores the evidence that allows us to say with confidence that atoms are not simply a useful idea — atoms exist.

Suitable for GCSE Chemistry, introductory A-Level Chemistry, revision, classroom display and independent study.

Keep asking why — because understanding is what chemistry is all about.