Category Archives: Awesome science videos

Alone in the night

Here’s a little something that I came across this evening – a time-lapse video of the Earth at night from the International Space Station (ISS). Enjoy!

Awesome science videos – Diet Coke and Mentos

An oldie but a goodie – I’m sure almost everybody has seen some version of this video, but I liked their theatricality. Enjoy!

Awesome science video of the week – Grape Plasma

This video is one that is incredibly interesting, but also quite difficult to explain simply. My warning – unless you’re prepared to risk your microwave being damaged beyond repair, don’t try this at home! Please also be warned that there is some coarse language in the video below.

Here is an attempt at an explanation; but just remember, I’m not a physics expert so this is just my best guess.  Firstly, the way that microwave ovens work is that a magnetron inside the microwave produces a large quantity of electromagnetic radiation in the microwave region of the spectrum (where the wavelength is about 12.5 cm in air).  These microwaves waves have less energy than visible light (so the idea that microwaves are hazardous is nonsense) but they just so happen to be at the right frequency to make water molecules vibrate more vigorously inside an object (such as food).  These vibrations cause heat to be released, heating up whatever object is inside the microwave – such as a grape, or last night’s leftovers!

The shape of the grape, especially when cut almost completely in half, means that the microwaves are amplified inside the grape, making it act like an antenna.  All this extra energy inside the grape means that the water inside the grape becomes superheated (i.e. to a temperature above 100 degrees) and escapes violently.  As best as I can tell, the reason that a plasma is created is because the water inside the grape is acidic and not pure, which means that it contains ions that conduct electricity.  When it escapes as superheated steam, the ions that are dissolved in the water allow an arc to be created between the water droplets, turning the steam into a plasma (which is essentially a gas with an electric charge) which emits a large amount of light. Phew!

Because the steam is what is causing the arcing effect, it needs to be contained under the glass, otherwise it will just dissipate and the arc will fizzle out.  I can’t completely explain why there appear to be flames when he first microwaves the grape; perhaps the sugars in the grape combust because of the heat?

I would appreciate comment from those who are more familiar with the physics, or if you just think I’ve got it all backwards!  For more information, you can check out other explanations here and here.

Awesome science video of the week – Elephant Toothpaste

As a part of providing something a little more interesting, I’ve decided to share an awesome science video with you each week – something creative, interesting or just downright bizarre.  Chemistry doesn’t need to be boring equations and lame test tube reactions that don’t work.  Sometimes a little bit of science is an awesome thing!

This week I’ve been teaching the chemistry bridging course at UTS, which is partly why it’s been a week since my last post.  As part of one of my lectures on the first day, we were looking at comparing the behaviour of water (H2O) and hydrogen peroxide (H2O2) – seeing how one tiny difference in the molecular formula has a profound effect on how a substance behaves.  So we watched a video on YouTube of the decomposition of hydrogen peroxide.  Now this reaction is normally very slow, but if we add a catalyst, the reaction becomes violently fast! Bubbles of oxygen gas are produced really, really quickly, which would normally just make it fizz a little, so nothing fun there.  But if we add a little detergent and food colouring to the mix, we make the magical Elephant Toothpaste! Enjoy!