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Thursday
Jun182009

Video Demo: Grain Silo Explosion

BubbleShare: Share photos - Easy Photo Sharing This is a very popular demo in science classes around the country. You need a coffee can with lid, candle, and irrigation tubing (slide 1). You can use cake flour, corn starch, or lycopodium powder. Put some of the substance into a petri dish. Light a match and place the flame next to the substance. The substance will brown but it won’t ignite. Place the substance into the coffee can next to the tube (use a drill to make a hole near the bottom of the can so the tube can fit). Light a candle (the best kind are the flat votive kind) and place it opposite the hole (slide 2). Put the lid on the can and make sure it is snugly fit. Take in a deep breath, then place the tube into your mouth and exhale a big breath. An small explosion will happen causing the lid to fly off. This demo demonstrates that for a substance to ignite it needs oxygen. When the substance is packed together there isn’t enough oxygen that surrounds the particles and ignition can’t occur. By blowing into the can the substance spreads apart, increasing the surface area, causing the ignition and the reaction happens very quickly.

Precautions: Wear goggles. Try this demo ahead of time to make sure it works safely. Make sure students are at a safe distance.

 

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