First, I had my students examine the conductivity of a puddle of water the size of a nickel. They checked for conductivity. Then they took a very small amount of sodium carbonate and a fresh puddle of water and pushed in a few crystals from the side. You can still see the crystals in the water but it tested positive for conductivity. They had to explain this. They did the same with a fresh puddle of water and a few crystals of copper (II) sulfate. Again, it tested positive for conductivity but they could still see the blue crystal. Finally, they started again with another fresh puddle of water, pushed a few crystals of sodium carbonate on one side and on the opposite side they pushed in a few crystals of copper (II) sulfate. After waiting five minutes, a solid dull blue precipitate formed in the middle. Also, the drop tested positive for conductivity.
An advantage to teaching on the trimester schedule allows me the opportunity to teach the same course again roughly twelve weeks later. So after grading my 2nd trimester students’ Chemistry B final exams, I was able to evaluate certain topics that caused my students problems, reflect on my teaching, and then determine how I was going to better prepare my students in the 3rd trimester chemistry B class.
1 class period
The juice from an orange peel causes a balloon to pop. When I first saw this effect I immediately thought to myself, “what is the chemistry involved in this experiment?” After quickly searching the web, I found several claims that a compound in orange peels called limonene (Figure 1) is responsible for this effect. Limonene is a hydrocarbon, which means that molecules of limonene are composed of only carbon and hydrogen atoms. Limonene is responsible for the wonderful smell of oranges, and it is a liquid at room temperature.
Last year I came across a link on Twitter regarding an art installation by Roger Hiorns in England titled “Seizure.” Some of you may have seen it too – a condemned flat in London was essentially sealed off and filled with more than 75,000 L of supersaturated copper sulfate solution.
A New Year with a New Volume of Resources The January 2015 issue marks the start of the 92nd volume of the Journal of Chemical Education and is now available online at http://pubs.acs.org/toc/jceda8/92/1. This issue features colorful chemistry; using stories and writing to learn; demystifying chemistry literature; cost-effective activities and materials; experimenting with chromatography and natural products.