Nov. 2, 2005

Puffed Rice Fleas

Static electricity brings your flea circus springing to life; explore the chemistry of electron interaction and like and unlike charges.

Description:

Kernels of puffed rice cereal behave like fleas when charged with static electricity.

You Will Need:

1. glass or porcelain dinner plate
2. puffed rice cereal
3. balloons
4. plastic comb
5. charging cloths (wool, plastic wrap, etc.)

Instructions:

This activity works best in low-humidity conditions.

Sprinkle several kernels of puffed rice cereal on the dinner plate. Use a charging cloth, which will create static electricity, to stroke an inflated balloon in one direction.

Bring the charged balloon near to the puffed rice. The kernels of cereal will jump off the plate and adhere to the surface of the balloon.

Hold the balloon motionless. Some of the kernels of puffed rice will jump from the balloon.

With practice, the balloon can be rotated immediately after collecting several kernels of rice, positioning the rice on the upper surface of the balloon. This should dispel the notion the rice is merely falling off the balloon rather than being repelled from it.

Content:

Puffed rice is a poor conductor. Similar to a charged balloon, an excess of electrons will collect on the surface of the kernel when it is charged with static electricity.

When a charged balloon is initially brought near to the kernels of puffed rice, the "unlike charge attracts" rule is demonstrated. The balloon is negatively charged with an excess of electrons. The rice has no charge. However, compared to the balloon, the rice has a relative positive charge. There exists a sufficient difference in charge to cause the rice to be attracted to the balloon.

Eventually some of the excess static charge on the surface of the balloon migrates to the rice, causing the rice to become negatively charged. The "like charges repel" rule is then demonstrated. Kernels of rice jump from the balloon.

Teacher's Notes

Activity excerpted by permission of the Chemical Educational Foundation (www.chemed.org) from You Be The Chemist. For additional information about these activities and lesson plans, see www.chemed.org/Kit.html.

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