Wednesday, March 25, 2009

[Chemistry Form 4] Particles In Motion

Do you know that it was the ancient Greeks who first suggested that everything is made up of particles? But when Democritus introduced the particulate nature of matter around 400BC, not many were convinced by his ideas.

In random
Centuries later, Brown, a Scottish scientist, observed that under the microscope, tiny particles of pollen floating on water move around in a haphazard fashion. When the pollen was examined on its own, no such movement was observed. This led to the idea that particles move randomly in a liquid or gas, and the movement is called Brownian motion.

Fusion of sorts
If a classmate has accidentally spilled an ammonia solution in the lab, you will soon know about it. Since particles of the ammonia gas move and mix with gas particles in the air, the sharp pungent smell of ammonia quickly spreads through the lab. When perticles mix like this, it is called diffusion.

Onion and tears
When you cut an onion, its cells are broken, and thus amino acid sulphoxides, which form suphenic acids, escape into the air. These acids release a volatile gas (propanethiol Soxide) which, upon exposure to moisture in your eyes or the air, changes into mild sulphuric acid. Diffusion of these compounds is responsible for the burning sensation in your eyes while cutting onions. Due to the eye irritation, your brain sends out impulses to your tear ducts, which respond to dilute the acid and protect your eyes.

detector : pengesan
diffusion : resapan
isotope : isotop
particulate : bersifat zarah
random : rawak
sterilise : membasmi kuman

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