Wednesday, February 12, 2014

Vanishing Valentine Chemistry Demonstration

Here's a fun chemistry demonstration that's perfect for Valentine's Day or to illustrate an oxidation-reduction reaction. The Vanishing Valentine involves shaking a solution, causing it to turn pink. If the pink Valentine solution is left undisturbed, it will become colorless. The color change cycle can be repeated several times. It is caused by the oxidation and reduction of resazurin. an indicator that is pink or colorless depending on its oxidation state.

Vanishing Valentine Materials

  • 100 ml of a 0.133 M dextrose solution (C6H12O6)
  • 100 ml of a 1.0 M sodium hydroxide solution (NaOH)
  • 1 ml of a 0.1% resazurin solution
  • a 250-ml or 500 ml Erlenmeyer flask or separatory funnel (resembles a heart)
  • stopper for the flask
  • dropper or pipette

Prepare the Solutions

Dextrose Solution: Dissolve 2.4 g of dextrose in distilled or deionized water to make 100 ml of solution. Sodium Hydroxide Solution: Prepare the 1.0 M sodium hydroxide solution by dissolving 4.0 g of sodium hydroxide in enough distilled or deionized water to make 100 ml of solution. Add the sodium hydroxide a little at time, stirring constantly. Heat is evolved from this reaction.
Resazurin Solution: Dissolve 0.1 g of resazurin in distilled or deionized water to make 100 ml of solution. The shelf life of resazurin solution is 6-12 months. This solution should be a deep blue color.

This Day in Science History - February 13 - Étienne Geoffroy

February 13th is Étienne François Geoffroy's birthday. Geoffroy was a French physician and chemist who was the first to arrange the known elements into a table based on their chemical affinity to each other.

Anyone who has ever mixed two items together knows some things combine better than others. In chemistry, two different chemical species' affinity is a property that shows how likely a chemical reaction will occur when mixed. Reagents with strong affinity are more likely to react with each other than reagents with little affinity to each other. Geoffroy's table had a series of reagents across the top with other reagents with high affinity with these elements listed below. This table became a standard table for 18th Century chemists until the end of the century when it was shown the amount of a reagent drove the reaction.

How Febreze Works

The other day I got frozen tiny shrimp to feed the jellyfish and pipefish in my aquarium. I used my fingers to drop a pinchful of shrimp into the water, which worked great except I smelled like I just got off a shrimp boat. Soap didn't touch the stink. Neither did stainless steel. So, I decided to Febreze myself. It worked great. Initially I smelled like flowers instead of shrimp, but the floral smell washed off, leaving my hands unscented.
Have you wondered whether Febreze actually removes odors or whether it just covers them with a perfume? Have you wondered how it works? Here's the lowdown on Febreze. It's a product that was invented by Procter & Gamble and introduced in 1996. The active ingredient in Febreze is beta-cyclodextrin, a carbohydrate. Beta-cyclodextrin is an 8-sugar ringed molecule that is formed via an enzymatic conversion of starch. The cyclodextrin molecule sort of resembles a donut. When you spray Febreze, the water in the product partially dissolves the odor, allowing it to form a complex inside the 'hole' of the cyclodextrin donut shape. The stink molecule is still there, but it can't bind to your odor receptors, so you can't smell it. Depending on the type of Febreze you're using, the odor might simply be deactivated or it might be replaced with something nice-smelling, like a fruity or floral fragrance. As Febreze dries, more and more of the odor molecules bind to the cyclodextrin, lowering the concentration of the molecules in air and eliminating the odor. If water is added once again, the odor molecules are released, allowing them to be washed away and truly removed.

Valentine's Day Chemistry

Romance is all about chemistry, right? Valentine's Day is February 14th, so you've still got time to find a great gift for your sweetie and impress him or her with your holiday knowledge. Here's some Valentine's Day chemistry content to help you out:
  • Vanishing Valentine Demo - Make a chemical solution go from blue to pink to clear.
  • Hot and Cold Valentine - A chemical solution goes from colorless to hot pink!
  • Crystal Heart - Grow a crystal heart as a decoration or gift.