Plasma Grape

CAUTION!! Be careful with this!! This experiment uses a knife AND a microwave, so you’re playing with things that slice and gets things hot. If you’re not careful you could cut yourself or burn yourself. Please use care!

We’re going to create the fourth state of matter in your microwave using food.  Note – this is NOT the kind of plasma doctors talk about that’s associated with blood.  These are two entirely different things that just happen to have the same name.  It’s like the word ‘trunk’, which could be either the storage compartment of a car or an elephant’s nose.  Make sense?

Plasma is what happens when you add enough energy (often in the form of raising the temperature) to a gas so that the electrons break free and start zinging around on their own.  Since electrons have a negative charge, having a bunch of free-riding electrons causes the gas to become electrically charged.  This gives some cool properties to the gas.  Anytime you have charged particles (like naked electrons) off on their own, they are referred to by scientists as ions.  Hopefully this makes the dry textbook definition make more sense now (“Plasma is an ionized gas.”)

So here’s what you need:

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• microwave (not a new or expensive one)
• a grape
• a knife with adult help

 
Download Student Worksheet & Exercises

1. Carefully cut the grape almost in half. You want to leave a bit of skin connecting the two halves.

2. Open the grape like a book. In other words, so that the two halves are next to one another still attached by the skin.

3. Put the grape into the microwave with the outside part of the grape facing down and the inside part facing up.

4. Close the door and set the microwave for ten seconds. You may want to dim the lights in the room.

You should see a bluish or yellowish light coming from the middle section of the grape. This is plasma! Be careful not to overcook the grape. It will smoke and stink if you let it overcook. Also, make sure the grape has time to cool before taking it out of the microwave.

Other places you can find plasma include neon signs, fluorescent lights, plasma globes, and small traces of it are found in a flame.

Note: This experiment creates a momentary, high-amp short-circuit in the oven, a lot like shorting your stereo with low-resistance speakers. It’s not good to operate a microwave for long periods with little to nothing in them.  This is why we only do it for a few seconds. While this normally isn’t a problem in most microwaves, don’t do this experiment with an expensive microwave or one that’s had consistent problems, as this might push it over the edge.

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