The color of a thermochromic system depends on its temperature. The colors of leuco dye-based systems can also be influenced by adding acids or bases to the thermochromic reactions. These can be used to create colorful demonstrations of acid-base chemistry. Thermochromism found in color changing cups can also be used to visualize heat flow, and therefore thermodynamic principles, associated with stretching and contracting elastomers.
HS-PS3-2: Motion of Particles and Energy of Position
This lab guides students through taking data and constructing their own heating curve for water. It requires no special equipment, is low prep, is safe, and can even be done at home for homeschool or distance learning. Even though the lab activity itself is relatively simple and straightforward, the concepts still engage students in higher level thinking and gives them important practice with laboratory techniques and forming hypotheses.
In this lab, students connect the workings of an electrochemical cell in the lab with the symbolic equations used in electrochemistry and manipulate a model representing the particulate level of what is happening during the electrochemical process. Although this lab was previously highlighted on ChemEd X, there are now virtual options offered!
In an effort to better understand my high school students' knowledge of what is happening during phase changes, heating curve calculations, and the ever popular can crush demo, I run them through a series of activities. First, I ask my students "What Temperature Does Water Boil At?"
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.
Last year while attending the Biennial Conference on Chemical Education at GVSU I had the opportunity to hear a talk that showed a video of a chemical demonstration showing the burning of magnesium metal. We have all seen many of these videos (thank you YouTube) and probably have performed this demo for our own students many times. During the video it may have been represented with a chemical equation followed by the students being asked to balance the equation or maybe even predict the products. Although the use of video including the showing of the equation nicely represents the macroscopic and symbolic representation, what was so unique about this particular video is that it also included the particulate representation embedded on top of the video of the demo. This was the first time I had seen the particulate level representation done like that and so I was intrigued in wanting to find more of these representations.
This lab was written as part of the Target Inquiry program at Grand Valley State University in Michigan. Students build an electrochemical cell, learn about the symbolic equations used in electrochemistry and manipulate a model representing the particulate level of what is happening during the electrochemical process.