So, you want to do a “Magic Show!” Student Presenter Packet for y-chem Outreach Program (10/11/2014)
Download 177.95 Kb.
|
- Navigate this page:
- □ Calcium carbonate reaction
- □ Sodium polyacrylate
- □ Memory Wire
- Potential Theme: “Chemistry is cool, and hot!”
- □ O 2 balloon cooled with liquid N 2
- □ Mg ribbon
□ Universal IndicatorDry ice is added to a purple solution. The solution proceeds through a sequence of color changes. Warning: Dry ice will freeze skin and cause “burns” Explanation/Teaching This solution is weakly basic and contains Universal Indicator, which changes color based on: [H+] or pH for older audiences “Chemical presence” for youngest audiences As we add dry ice, the CO2 dissolves in the water and reacts to form carbonic acid, which changes the pH of the system, changing the color Basic condition is blue, acidic condition is yellow/peach Presentation suggestions Add a small piece of dry ice first. If there is no color change within 5 seconds add a second piece, and so on. You can add additional NaOH (if provided) to change solution back to purple. □ Calcium carbonate reactionTwo clear colorless solution are mixed, generating a white precipitate. Explanation/Teaching Two colorless solutions create an insoluble compound. Presentation suggestions CaCO3 is a main component of chalk. Other ideas might be cave chemistry, and hard water stains on faucets. □ Sodium polyacrylateA powder is added to a small amount of water. The water quickly gels. Conversely, water can be added to a plastic cup containing the powder; the cup is inverted without the water pouring out. Explanation/Teaching This is the stuff found in diapers, it can absorb up to 200 times its weight in water Presentation suggestions Put a small amount of the powder in the bottom of a white Dixie cup, and have a second Dixie cup that is empty. Show the children that both cups are “empty” (the powder will blend in with the cups and they won’t see it). Pour a small amount of water into the truly empty cup, and then pour it from the empty cup into the cup with the powder. Attempt to pour the water back into the other cup, and ask “Where did the water go?” □ Memory WireA piece of wire in the shape of a block letter “U” is dropped into a bath of boiling water. The wire immediately changes shape to a block letter Y. The wire can be easily shaped and bent, but when returned to the boiling water, quickly forms the block letter “Y.” Warning: Care must be taken to with the hot plate needed to generate the boiling water to avoid burns and fires. Explanation Elementary School: Browse for the story of how it was discovered by William J. Buehler, a researcher at the Naval Ordnance Laboratory, and summarize your findings. High School: Explain that there are two solid phases, and when you heat it above a certain temperature, it changes to the second phase, which moves to a more energetically favorable orientation (the shape you have pre-set) Presentation suggestions Hold up the U again a contrasting background. Ask the students “What happens when you put the heat to the U?” Carefully drop the wire frame into the boiling water so that it lands flat (if you don’t it can violently jump out). Using tongs, pull out the wire, hold it against the high contrast background, and declare, “The Y comes out on top!” Potential Theme: “Chemistry is cool, and hot!”□ Gun cotton / Regular cottonCommercial cotton is ignited on a ceramic tile. The cotton slowly burns. Chemically modified cotton is also ignited on a ceramic tile, but erupts quickly in a bright, fiery flash. Warning: Some batches burn slower than others. Only ignite the cotton on the provided tile. Explanation Cotton is made of cellulose, which burns slowly. When cotton is soaked in fuming nitric acid, the hydroxyl groups are replaced by nitro groups, making it combust much quicker (the same step used to make the ‘N’ in ‘TNT’). Presentation suggestions The following is from the Wikipedia article on gun cotton: Christian Friedrich Schönbein, a German-Swiss chemist, discovered a more practical solution around 1846. As he was working in the kitchen of his home in Basle, he spilled a bottle of concentrated nitric acid on the kitchen table. He reached for the nearest cloth, a cotton apron, and wiped it up. He hung the apron on the stove door to dry, and, as soon as it was dry, there was a flash as the apron exploded. (http://en.wikipedia.org/wiki/Gun_cotton) Great with the lights out. □ O2 balloon cooled with liquid N2A balloon filled with oxygen is lowered into a dewar filled with liquid nitrogen. The balloon almost completely deflates. When the balloon is removed from the dewar, the balloon re-inflates. Warning: Liquid nitrogen is much colder than dry ice, and will quickly freeze and burn skin. Be aware where the liquid nitrogen drips. Explanation/Teaching Oxygen gas turns to a liquid at the temperature of the liquid nitrogen. There are no molecules pushing on the inside of the balloon to keep it inflated. Presentation suggestions If you can form the long balloon into a shape (like a dog or a sword – quite easy, ask Dr. Macedone to show you), the audience can be a little more involved as you deflate the structure in the liquid nitrogen. □ Mg ribbonWhen a strip of magnesium metal is ignited with a blow torch, the metal burns and intense and brilliant white. Students can see the spectrum using diffraction glasses. Explanation/Teaching The magnesium metal is hot and reacting with oxygen in the air. This is the bright white color in fireworks. Presentation suggestions The visual appeal of the burning magnesium wire is enhanced by viewing the event through the diffraction glasses, suggest looking slightly to the side of the ribbon. Great with the lights out. Directory: wp-content -> uploads -> 2014 2014 -> For want of a nail 2014 -> Stop Militarizing Law Enforcement Act of 2014 2014 -> Ihbb asian Championships 2014 middle school bowl Round 4 First Quarter 2014 -> Ihbb european Championships 2014 Bowl Round 4 First Quarter 2014 -> International History Bee and Bowl 2013-14 Asian Division Question Set Bowl Round Six 2014 -> United states patent and trademark office 2014 -> Coffs harbour eisteddfod vocal syllabus 2014 -> Listen News Programs Schedule pledge now 2014 -> Slow club announce third album complete surrender Download 177.95 Kb. Share with your friends:
|