Make smoke or fog using dry ice, nitrogen, water fog or a glycol. Any of these Halloween chem demos can be used to teach important chemistry concepts relating to phase changes and vapor.This Halloween color change demonstration is based on an acid-base reaction. This is a good opportunity to discuss how pH indicators work and to identify chemicals which can be used to elicit color changes.The Old Nassau or Halloween reaction is a clock reaction in which the color of a chemical solution changes from orange to black. You can discuss how an oscillating clock is made and what conditions might affect the rate of oscillation.This is a dry ice Halloween demonstration in which you make a sort of crystal ball using bubble solution filled with dry ice. What is neat about this demonstration is that the bubble will achieve a steady-state condition, so you can explain why the bubble reaches a size and maintains it rather than popping.Use an historically important chemical reaction to produce acetylene gas. Ignite the gas in a prepared pumpkin to cause the jack-o-lantern to carve itself!<p>Turn boring lifeless gummy worms into creepy zombie Frankenworms using a simple chemical reaction.</p>Here&#39;s a chemical reaction that appears to make blood (but really it&#39;s a colored iron complex). You treat a knife blade and another object (such as your skin) so that when the two chemicals come into contact &#34;blood&#34; will be produced.There&#39;s something eerie about green fire that just screams &#34;Halloween.&#34; Explain how flame tests work then illustrate how metal salts can affect a fire by using a boron compound to produce green flames. Perform the reaction inside a jack-o-lantern for added effect.The dye used to make goldenrod paper is a pH indicator that changes to red or magenta when exposed to a base. If the base is a liquid, it looks as though the paper is bleeding! Goldenrod paper is great anytime you need inexpensive pH paper and perfect for Halloween experiments.