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Homeschool Chemistry 101 — Day 3

March 20, 2014

Introduction to Chemistry

By Daniel H. Vestal, AmeriCorps Museum Investigate Lab Educator

Wednesday, March 19 marked the third installment of the homeschool chemistry series in the Natural World iLab.  Dr. Holly reviewed a few things in Week #2. One of the topics was phase changes between solids, liquids, and gases. She reminded the chemists how evaporation creates a gas, condensation creates a liquid, and liquids cool to create a solid.

She led the class in an activity describing the different evaporative rates of water and rubbing alcohol. The students made a bulk flow initiator (paper fan) to stimulate the liquids to evaporate. With digital thermometers the students were able to calculate in Celsius the degree change from a liquid to a gas. Which brought us to a demonstration from Mr. Bob.

Mr. Bob used a boiling flask, fractionating column, and condenser to distill alcohol from a mixture of water and alcohol. This distillation process illustrated how heat is needed to move liquid into a gas phase. Since alcohol’s molecular bonds are weaker than the hydrogen bonds in water, alcohol boils out of the mixture first.  Another experiment that has been nicknamed the “warm pig” was produced by using a water cooler jug (dressed like a pig), ethanol, and a lighter. With a capful of ethanol and a flick of the lighter, a flaming vortex of blue fire blasted out of the jug. Afterwards the students took turns touching the jug, which felt very warm, hence the nickname.

After that Dr. Holly went into detail about homogeneous and heterogeneous mixtures and provided several examples. Saltwater, which is mixed thoroughly and evenly throughout is a homogeneous mixture. Beach sand is heterogeneous, meaning that it has an uneven mixture of shells, seaweed, and sand.

The young chemists made solutions by mixing three chemicals into water and measuring the heat produced. The first chemical dissolved was sodium chloride, followed by calcium chloride, and ending with ammonium nitrate. With sodium chloride there was little to no difference in temperature; with calcium chloride it was evident the water solution heated up quickly; and finally, with ammonium nitrate, the homeschoolers noticed that the solution was actually cooling down rapidly.

The last part dealt with boiling point elevation and freezing point depression. The chemists learned first-hand what happens when salt is added to ice water. It can be compared to what happens when the Department of Transportation salt and brine trucks spread the mixture on the roads: the salt decreases the temperature that it takes for water to freeze.  At first this may not make sense, but if the roads covered with salt create a layer requiring water to be colder than 32⁰ F to freeze, it prevents ice from forming.

After learning the effects salt has on reducing the freezing point, the young scientists got buckets of ice water, spread a pinch or so of salt over the ice and laid a piece of string on top. After a few minutes, the ice began to clump together around the string and held fast. Each person lifted their string out of the water. The idea was that the ice cubes would be stuck to the string; however, results for this particular experiment were mixed.

The favorite experiment of the day included pouring orange juice into a small Ziploc bag, which was placed inside a larger Ziploc bag containing ice and lots of table salt. They were instructed by Mr. Bob to shake the bags for five minutes, or until the OJ had turned into a slushy. With a lower freezing point the very cold water froze the orange juice quickly.  Once it had transformed, the homeschoolers were allowed to consume the product they created using the principles of chemistry. YUM!

Young chemists making delicious orange slushies.

Chemists making delicious orange slushies.

Our chemistry series will end next Wednesday, however, if you want to stay informed for future programs, head to the Museum’s website and sign up today!

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