Final answer:
The statement about Brownian motion being the random motion of particles in fluids observable under a microscope is true. It was first described by Robert Brown and provides nearly direct evidence of the existence of atoms and molecules.
Step-by-step explanation:
The statement that Brownian motion is the random motion of particles suspended in gases and liquids that can be observed under a microscope is true. Brownian motion was first observed by Scottish botanist Robert Brown in 1827 when he saw pollen grains moving in complex paths suspended in water. This random motion is caused by the collisions of fluid molecules with the suspended particles, leading to their erratic path.
Through observing Brownian motion, one can infer the existence of molecules since the movement of the visible particles is the result of statistical fluctuations in the number of molecules striking the particle from different directions. Under a microscope, this random to and fro movement, which can also be described as diffusion of many particles, serves as nearly direct evidence for the existence of atoms and molecules, a foundational concept in physics and chemistry.
Brownian motion is not only a fascinating topic to explore under a microscope but also provides important insights into the nature of matter at the microscopic level.