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Homeschool Chemistry 101 — Day 4

March 28, 2014

Introduction to Chemistry

By Daniel H. Vestal, AmeriCorps Museum Investigate Lab Educator

March 26, 2014 marked the grand finale to our Introduction to Chemistry series, “Whiz, Bang and Ewww!”, with a rousing request for an encore. Before I go any further in this final posting of the series, I want to thank the homeschool students and parents who attended. I am very appreciative to witness the beginnings of future lab researchers and chemists. I hope you enjoyed the series as much as I did.

For our final session, both our chemists, Dr. Holly and Dr. Katey, as well as Mr. Bob, discussed polymers, both natural and synthetic, as well as titrations and the interaction of acids and bases. The young scientists were split into three groups. Dr. Katey’s group learned about pH; each student tested various household materials to determine acidity or alkalinity. A second group was lead by Mr. Bob, who discussed the nitrogen cycle in aquatic environments, with students testing water samples for ammonia. Dr. Holly taught the very important skill of titration. An important concept learned in the class was pH.

pH stands for “power of hydrogen” in a liquid concentration. The pH scale ranges from 0, which is strongly acidic, to 14, which is strongly basic. By measuring the amount of hydrogen ions, chemists can determine the acidity of a liquid. It was surprising to think of everyday things as being an acid or a base. Take, for instance, soda drinks. When you take a sip of soda, keep in mind that it is an acid and is capable of breaking down the enamel of your teeth! An example of a base is ordinary baking soda at pH level 9.5. Pure water sits right in the middle with a pH of 7, which is neutral.

The young scientists in Dr. Katey’s group used a universal indicator fluid to determine the pH levels of baking soda, bleach, borax, dish soap, lemon juice, saltwater, sprite, and vinegar. By squeezing a few drops of the liquid into a sample, it causes an immediate color change. After comparing this to a colored pH scale, the homeschoolers were able to define each substance as an acid or base and the level of pH.

In Mr. Bob’s group, they tested for high and low concentrations of ammonia in water samples taken from the fish aquarium, the mosquito-rearing tank, and the duckweed pond. Even moderate concentrations of ammonia is toxic to fish and amphibians. Aquatic plants need nitrogen and ammonia is a source of this. However, too much can quickly lead to algae blooms. Those blooms can restrict oxygen in the water, particularly at night, or when they die and decompose, leading to fish kills.

To test the level of ammonia the homeschoolers used a two part chemical test that led to a color change indicating the level of ammonia. Their investigations revealed the level of ammonia in the aquarium water was neutral, the mosquito water was low in ammonia, and the duckweed had the highest concentration of ammonia. Bob explained that the high level of ammonia in the duckweed was probably from the fertilizer he added to the duckweed pond two days prior.

Dr. Holly’s group learned how to do titration. Titration is a laboratory method used to determine an unknown concentration of a known component, like an acid. You may know it’s an acid but don’t know the concentration. Titration is the process that reveals the answer.

The first step was filling a tall, glass burette up to the 0mL mark with sodium hydroxide. 10mLs of an unknown concentration of vinegar solution was poured into an Erlenmeyer flask. With a few drops of phenolphthalein, added to the vinegar as a color indicator, the titration was ready to begin. Slowly, carefully, and drop by drop, students added minute amounts of sodium hydroxide into the vinegar solution. Suddenly the color fuchsia magically appeared. With Dr. Holly translating the results, the unknown concentration of acid was determined!

Young chemist concentrating on his titration experiment.

Determined titration chemist. Photo by Karen Swain.

Finally the moment that all of them were waiting for —polymers! Dr. Katey discussed how in nature and in the world of chemistry there are natural polymers such as wool or DNA and synthetic polymers such as nylon and silicone. To demonstrate a natural polymer, chemists took cornstarch and water to create a simple polymer also known as “oobleck” after the Dr. Seuss’s children’s book entitled Bartholomew and the Oobleck. This non-Newtonian fluid resembles a liquid, but it is also a solid. If you scraped your finger across the top of the oobleck it felt dry, but if you let your finger sit on top it sank like quicksand.

For the next experiment the young scientists needed to put on their goggles and gloves. Under close supervision, they took both part A and part B of a polyurethane compound and mixed it to create polyfoam “ice cream” (non-edible of course). In its liquid form it could be mildly harmful if it touched the skin, but after it dries into a solid it is harmless. I still would not recommend trying to lick or eat the “ice cream” though.

For the final experiment with polymers, students created their own homemade green Silly Putty! Yay! Just by mixing three household items (white Elmer’s glue, water, and household detergent), a Silly Putty-like polymer was fabricated. I even made some for myself and couldn’t stop playing with it!

A young chemist astonished by her homemade Silly Putty.

Young chemist astonished by homemade Silly Putty. Photo by Karen Swain.

Again, I just want to thank all of the people who attended the four part series and those that have already requested more. It is in the works! If you would like to try out one of our homeschool programs or other classes, head to the Museum’s website, click, register, and come!

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2 Comments leave one →
  1. December 22, 2015 2:42 pm

    I will right away seize your rss fee as I cann not
    to find your email subscription hyperlink or newsletter service.
    Do you’ve any? Kindly permit me recognize so that
    I could subscribe. Thanks.

    • February 3, 2016 8:09 am

      Sorry that it took over a month to respond. I regret to inform you, I am no longer with the North Carolina Museum of Natural Sciences.

      The best person to reach out to is the Natural World iLab coordinator, Bob Alderink. His contact information is available on http://naturalsciences.org/staff/bob-alderink.

      Again, I apologize for any inconvenience this may have caused. Take care.

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