![]() ![]() ![]() Sometimes pushes from all directions would be equal and you would not move. You would find people bumping into you from all sides. Imagine yourself caught in the middle of a large crowd of people who are undecided as to which way they should go. When that happens, the particle will respond to the unbalanced force and move accordingly. ![]() However, since molecular motion is random, there will be moments when the particle is struck by more molecules moving in one direction than in any other. Since particles such as pollen are thousands of times larger than water molecules, we would expect that on the average the particle would be hit as many times by water molecules on one side as it would be by molecules striking it from the opposite direction. According to this theory, Brownian motion is the result of collisions between the small microscopic particles and the invisible but constantly moving water or air molecules surrounding them. Others found the same strange motion when they observed tiny inanimate particles of dye, dust, smoke, or soot.īrown could offer no explanation for his observation, which became known as Brownian motion nor could anyone else, until James Clerk Maxwell (1831 –1879) and others developed the kinetic molecular theory a generation later. He thought that the motion might be related to life processes within the pollen, but later he observed the same kind of zigzag motion with pollen from plants that had been dead for many years. As he watched the tiny particles of pollen under his microscope, Brown noticed that they were constantly jiggling about. In 1827, Robert Brown (1773 –1858), a Scottish botanist, prepared a slide by adding a drop of water to pollen grains. Brownian motion is the constant, but irregular, zigzag motion of small colloidal particles such as smoke, soot, dust, or pollen that can be seen quite clearly through a microscope. ![]()
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