A great experiment to demonstrate the existence of atoms is Brownian motion, originally observed by Robert Brown in 1827.
Here’s how the curious chemist in you can try it:
Brownian Motion Experiment
Materials Needed:
A microscope
A glass slide
Water
Pollen grains or dust or soot particles
Procedure:
Place a small drop of water on a glass slide.
Sprinkle a few pollen grains or fine dust or soot particles into the water.
Observe under the microscope at high magnification.
Observation: The tiny particles will not remain still; instead, it is seen to follow a constant, unpredictable zigzag pattern, as if they were colliding with unseen forces, abruptly changing direction upon impact.
Why It Works: Albert Einstein used Brownian motion as evidence for the existence of atoms and molecules. He explained that the jittery movement of pollen grains was caused by random collisions with invisible atoms of water molecules, causing them to "dance." He mathematically explained this motion in 1905, confirming the atomic theory. Atomic theory states that all matter is made up of tiny, invisible, indivisible particles called atoms.
Related Content – What is a Brownian Motion?