Discrepant Event: Flaming Snowball Gabrielle Alberni Lynn Peters Description: We will be mixing a solution containing Calcium Acetate dissolved in water with a liquid solution of 95% Ethanol then observing what is produced. Curriculum: Senior 1: S1-2-11 S1-2-12 S1-2-13 S1-2-14 Properties of Substances Physical versus chemical changes Determine the indicators of chemical changes Combustion Senior 2: S2-2-05 S2-2-06 S2-2-07 Conservation of Mass Balancing equations Classify chemical reactions Senior 3: C11-3 C11-4 Chemical Reactions Solutions: Polar vs. Non-Polar Materials: 2 * 500 ml beaker 300 ml beaker Calcium Acetate 95% Ethanol Sink (nearby) Water Two metal bins (1 empty, 1 with water) Fire Extinguisher Paper Towel Matches Marshmallows and roasting sticks Procedure: First, we will prepare two solutions in separate beakers. Solution A will contain 50ml of water and 6g of Calcium Acetate. Mix the two until most of the Calcium Acetate is dissolved in the water and the solution looks clear. Solution B is 150ml of 95% Ethanol in a 500ml beaker. Now we will ask the class if they can predict what will happen when we mix the two solutions. Students can talk amongst each other and write down their prediction. Pour solution A into solution B and observe. Immediately, we will see that a gel has formed inside the beaker The next step should be performed near a sink. We will remove the material from the beaker then shape into a ball. This will be done over a sink to catch the excess ethanol. After handling the “snowball” wash hands well, then make sure they are dried as well. Student volunteers can touch the “snowball” to feel the texture and temperature of it. Place the ball in an empty metal bin, or something that is safe and not flammable, and then light it with a match. Having the classroom lights out will be the best way to see the flame. The first demonstration will be to pick up the flaming ball and explain how it feels. Make sure you dip your hands in the tub of water first so it doesn’t burn hands. Student volunteers will be asked to handle the burning ball and explain how it feels in terms of temperature. Ethanol burns at a lower temperature than other substances which allows for it to be held while burning. The second demonstration is to roast a marshmallow using the flaming ball. This will show the whole class that the “flaming snowball” is giving off heat. At the end of the presentation, the flame will be extinguished by covering it with a clean dry beaker. Principles: A physical change occurs when liquid ethanol is poured into the clear saturated calcium acetate solution. This forms a solid gel. This gel is similar to “Sterno”, a gel which is used as fuel in portable cooking stoves. The calcium acetate molecules are polar and readily dissolve in the polar water molecules. When the saturated calcium acetate (polar) is mixed with the ethanol (nonpolar), the acetate molecules precipitate and form a gel. This gel consists of a liquid (alcohol) dispersed throughout a solid (acetate). The “snowball” consists of calcium hydroxide (Ca(OH)2) with ethanol (CH3CH2OH) in it. Once ignited, the ethanol reacts with oxygen to create a flame. Note that the flame is fairly clear and thus to prove that there is indeed a flame you could for example roast a marshmallow. If the gel were placed into an empty tuna can, and ignited, it would produce enough heat to fry anything for a period of about 22 minutes. Gel formation: + Liquid (CH3COO)2Ca + Calcium Acetate Liquid 2 CH3CH2OH Ethanol Liquid (top layer) + Solid (bottom layer) 2 CH3COOCH2CH3 + Ca(OH)2 Ethyl Ethanoate Calcium Hydroxide Combustion Reaction: 2 CH3CH2OH + Ethanol (in the snowball) 6 O2 + 4 CO2 + 6 H2O This event is likely to create disequilibrium because the gel looks like a “snowball” that is lite on fire. This demonstration is also discrepent in the fact that when the saturated calcium acetate solution is mixed with the ethanol it forms a gel. (liquid + liquid solid) Safety Concerns: Ethanol is very flammable so make sure there isn’t anything that can catch on fire nearby. Do experiment with a partner so handling is easier, and one is always cleaning up to keep area safe. Don’t breathe in the Calcium Acetate directly. When removing jelly substance from the beaker, do it over a sink so the excess ethanol isn’t present in the experiment working area. Make sure the surface where the “snowball” will be lit is completely dry. Hold the flaming snowball with clean hands only and make sure there’s no ethanol on your skin from previous steps. Have a metal container with water nearby to wet hands before handling the flaming snowball. Be careful while handling the snowball because if dropped, it will break into many flaming pieces. Distinguish the flame before it gets very hot. References: http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA2/CCAMAIN.HTM http://www.wikihow.com/Make-a-Flaming-California-Snowball Experiment: Flaming Snowball Name: _____________________