Imploding tankers, or when chemistry finally got interesting

I knew the moment that my chemistry professor showed this video in lecture, I had to post it to the blog. From looking at the tanker, you’d expect it to be built well enough to handle some brutal conditions. Instead, the poor thing got crushed like a soda can under someone’s foot. So, what caused such a dramatic end to the tanker? The simple laws of pressure. Basically, as the tanker was drained of its contents the volume decreased which caused an increase in pressure, thereby crushing the tanker (Correction:As the tanker was drained of its contents, the pressure was decreased inside the tanker, while the pressure on the outside remained the same. With the decrease in pressure on the inside, the external pressure was able to crush the tanker. With that being said, they had to be using a pump to vacuum out the contents of the tanker without air being let in. Thanks Jamie!). On a molecular level, it’s a little more complex. The air we breath is made up of molecules of oxygen, nitrogen and very small amounts of other compounds. On their own, these molecules just bounce around and their impact creates pressure. This results in a relatively modest 14.7 pounds of pressure per square inch at the earth’s surface. This is commonly referred to as 1 bar of atmosphere, or atm. To put that into context, our sister planet Venus sits at around 93 bars.

These facts were originally postulated by Robert Boyle and can be summed up in Boyle’s Law: when volume decreases, pressure increases. When the same number of molecules are squished into an area much smaller than before, the excitation increases causing an equal increase in pressure (Further edit: in the case of the tanker, the exact opposite occurred). Had the tanker from the video been properly vented prior to draining, the pressure would have remained the same and the tanker could have been used for other things than scrap metal. But had they done that, we wouldn’t have such an awesome video to show off the power of pressure.