INTRODUCTION Besides being a complex science, chemistry can be also fun and interesting. This is most clearly illustrated through the chemical experiment. The experiment is the side of chemistry that attracts the attention of students of different ages to this difficult and simultaneously interesting science. The use of the experiment in education increases the interest and motivation, provokes the learners, excites them and provokes expectations and impatience. It is necessary to use the scientific experiment as a method of illustration in teaching. Each subject in chemistry can be presented or touched with the experiment. This in turn contributes to the easier learning of the study material. We are also able to demonstrate the relationship between the attractiveness and the scientific side of the chemical experiment. The point of this communication is to apply the relationship between science and attractiveness particularly in studying the periodic system. HOT ICE Sodium acetate, NaCh3COO, also abbreviated NaOAc, is the sodium salt of acetic acid. This colorless deliquescent salt has a wide range of uses. This sodium acetate is also used in heating pads, had warmers and hot ice. It trihydrates crystals met at 58’C dissolving in their water of crystallization. When they are heated past the melting point and subsequently allowed to cool, the aqueous solution becomes superstated. This solution is capable of cooling to room temperature without forming crystals. Sodium acetate or hot ice is an amazing chemical you can prepare yourself from baking soda and vinegar. You can cool a solution of sodium acetate below its melting point and then cause the liquid to crystallize. The crystallization is an exothermic process, so the resulting ice is hot. Solidification occurs so quickly you can form sculptures as you pour the hot ice. Health and Safety: This experiment involves boiling solutions. Please take care when doing so and ensure you have adult supervision. You will Need: 4 tablespoons of baking soda 1 litre clear vinegar The concepts it illustrates are: Supercooling, Crystallisation, Exothermic, Chemical Reactions What to Do: In a saucepan, add baking soda to the vinegar, a little at a time and stirring between additions. The baking soda and vinegar react to form sodium acetate and carbon dioxide gas. If you don’t add the baking soda slowly, you’ll essentially get a baking soda and vinegar volcano, which would overflow your container. You’ve made the sodium acetate, but it is too dilute to be very useful, so you need to remove most of the water. Here is the reaction between the baking soda and vinegar to produce the sodium acetate: Na+[HCO3]– + CH3–COOH → CH3–COO– Na+ + H2O + CO2 Boil the solution to concentrate the sodium acetate. You could just remove the solution from heat once you have 100-150 ml of solution remaining, but the easiest way to get good results is to simply boil the solution until a crystal skin or film starts to form on the surface. This should take about an hour on the stove over medium heat. If you use lower heat you are less likely to get yellow or brown liquid, but it will take longer. Some discolouration is normal. Once you remove the sodium acetate solution from heat, immediately cover it to prevent any further evaporation. Pour the solution into a separate container and cover with plastic wrap. You should not have any crystals in your solution. If you do have crystals, stir a very small amount of water or vinegar into the solution, just sufficient to dissolve the crystals. Place the covered container of sodium acetate solution in the refrigerator to chill and await the amazing results! The Science Behind Hot Ice The sodium acetate solution in the refrigerator is what is called a supercooled liquid. That means the sodium acetate is in liquid form below its usual melting point. Once you touch, bump, or add a small crystal that is not liquid, crystallization will begin and the liquid will change to a solid. When the molecules in the solute (sodium acetate) are in a solution, they normally are surrounded by a solvent (in this case water molecules). Occasionally, a few solute molecules will bump into each other and stick together for a little while but they will eventually break apart. If enough solute molecules stick together, they can overcome the forces in the solvent that would normally break the solute molecules apart. When that happens, the clump of solute molecules serves as a seed (or nucleation site) for other solute molecules to cling to so the crystallization process can take off again. The sodium acetate powder we placed on the plate acted as a nucleation site for the dissolved sodium acetate in the solutions. The crystallizing sodium acetate releases energy in the form of heat and is an example of an exothermic process. Sodium acetate is often used in hand warmers as it release heat when crystallizing. FIRE CARBON SNAKE Carbon is one of the basic elements of matter (Bush 1230-1231). The name carbon comes from the Latin word "carbo" meaning charcoal.Carbon is the sixth most abundant element (Gangson). More than 1,000,000 compounds are made from carbon(Carbon (C)). "The Element Carbon is defined as a naturally abundant non-metallic element that occurs in many inorganic and in all organic compounds, exists freely as graphite and diamond and as a constituent of coal, limestone, and petroleum, and is capable of chemical self-bonding to form an enormous number of chemically, biologically, and commercially important molecules." Carbon is used in diamonds, petroleum oil, radiocarbon dating, smoke detectors, kerosine, gasoline, carbon fiber. (Alcin). Carbon is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent-making four electrons available to form covalent chemical bonds. It belongs to Group 14 of the periodic table. LANGKAH BERHATI-HATI CARBON SNAKE Make a fiery black snake rise from the ground with this exciting experiment! Using simple household ingredients, learn how a burning mixture of baking soda and sugar can create a stunning carbon snake. Always be careful when conducting experiments involving fire. Be sure to only light the sand on a safe fireproof base in a well ventilated area. Keep water nearby as a precaution. Remember to tie back long hair and never leave flames unattended or unsupervised by an adult. Prep Work This experiment requires dry sand. Your sand might be damp if you get it from somewhere that is in contact with the ground, like a sandbox. If needed, spread your sand out on a baking tray and place it in direct sunlight or in the oven until it is completely dry. Only do this experiment with adult supervision, in a location where it is safe to have a small fire. Have a fire extinguisher accessible for emergencies. STEPS CARBON SNAKE Sand Baking soda Sugar Small ceramic plate or bowl Small cup Measuring spoons Lighter fluid Long lighter or matches 1. In a bowl, combine 4 tsp of powdered sugar with 1 tsp of baking soda 2. Fill the pie tin with sand and create a small mound in the middle. Use your knuckle to make an indent in the middle of the mound. 3. Pour lighter fluid on the mound and in the indentation. Make sure that the sand is well soaked. 4. Spoon your sugar and baking soda mix into the center of the mound. 5. Carefully light the sand near the sugar mixture. (An adult should perform or carefully supervise this step, if needed.) The sugar and baking soda mix will begin to bubble and turn black. As this mixture burns, watch as your snake begins to grow and take shape. It is a slow process so be patient! A snake will begin to form after a couple minutes and can continue to burn for over 20 min! EXPLANATION CARBON SNAKE Your carbon sugar snake is the product of three chemical reactions that are all dependent on heat. The first of these reactions occurs when sugar combusts (burns) in the presence of oxygen. This produces carbon dioxide gas and water vapor (also a gas), which pushes more of the sugar/baking soda mixture upwards. Some of this additional sugar heats up but doesn’t have access to any oxygen, so instead of burning, it undergoes thermal decomposition, producing solid carbon and more water vapor. This solid carbon now gives the snake some shape, and also gives the snake its black color. Lastly, the baking soda also decomposes in the heat, producing solid sodium carbonate, and carbon dioxide gas and water vapor. Altogether, these three reactions produce both the solid components of the snake (carbon and sodium carbonate) and hot gases (CO2 and water vapor) that expand and inflate the snake up and out of the sand bowl. The sand in this experiment doesn’t chemically react with anything in the growing snake. Instead, it evenly distributes the heat from the burning lighter fluid to the sugar and the baking soda, ensuring a slow, steady burn and the growth of a long carbon sugar snake. What Happened? When you set the lighter fluid on fire, the sugar and baking soda mixture also started to burn. As it burned, it created gas bubbles that got trapped, resulting in the black "snake" structure that rose out of the flames. The snake grows slowly, and may take 10–20 minutes to reach full size. It might be surprising that the snake is so big and seemingly comes out of nowhere, but if you wait until it cools and then poke it or pick it up, you will see that it is extremely lightweight, like foam. See the Digging Deeper section to learn more about the chemical reaction that creates the fire snake. Digging Deeper Table sugar, also called sucrose, is a chemical compound that contains lots of carbon. Its chemical formula is C12H22O11. Sugar can be oxidized, which means that it can react with oxygen to form other products. When you expose sugar to an open flame, it will burn quickly and react with the oxygen in the air. This is called a combustion reaction. The end products are carbon dioxide (CO2) and water (H2O). A different reaction happens if there is not enough oxygen present during the combustion to form CO2. In this case, the sugar decomposes, resulting in elemental black carbon (C), or charcoal. The baking soda (sodium bicarbonate, NaHCO3) decomposes at high temperatures and releases lots of CO2. The production of high amounts of CO2 causes a lack of oxygen. This means that there is not enough oxygen for all the sugar to be converted into CO2 and water via a combustion reaction. Instead, some of the sugar decomposes into elemental carbon and starts forming the solid black snake-like structure. The carbon dioxide gas and water vapor push the sugar and baking soda mixture upwards. At the same time, these gases get trapped in the solid carbon, creating the lightweight foam snake that you see emerging from the sand.
