Video starts at 1:40 (the coolest part of the video)
How to microwave a grape and create plasma you ask?
Take a seedless grape and slice it mostly in half, not all the way through. You have to leave a small amount of skin connecting the halves. Put it wet side up in your microwave with a glass over it. Turn it on for 10 seconds, and voila! A flaming light show with loud buzzing sounds!
Warning: This is supposed to be bad for your microwave’s magnetron so maybe you shouldn’t do it if you don’t want to ruin your microwave. Also it will generate ozone gas which is not healthy to breathe in so when you’re done with the show, open the door and walk way until it is diffused.
Why does this happen?
The brilliant light display is powered by the electricity the microwave is putting into it. The microwave provides a strong electric field channeled by the grapes. The skin of the grape acts as a good dielectric so when you cut one in half they channel a lot of power into the gap between them, strong enough to ionize the air. Once the air is ionized it becomes plasma. The grape is merely an antenna concentrating the energy into a light display.
A lit match does it, too, but even better.
What is plasma?
Plasma is a state of matter where atoms are ionized – i.e, have lost some electrons. When a strong electric field goes through a gas (such as air in the microwave) you can ionize the gas. The bright ball of light you see are from the electrons recombining with the atoms as the gas becomes electrically neutral again.
If you want to learn more of the science behind this phenomena, you can check out this link.
Hope you found that interesting!