If rhubarb stem is placed in a solution of permanganate, the purple permanganate ion is reduced to the colorless Mn2+ ion. It is thought that the oxalic acid present in rhubarb causes this reduction. The investigations presented in this post provide evidence that this may not be the whole story...
I found a version of this demonstration online a couple of years ago. I admit, when I first tried it with my class it was mostly for a crowd pleaser to demonstrate the activity series of metals, but I then became very intrigued by the processes occurring. The original source only referenced the “single replacement reaction” between Mg(s) and AgNO3(aq). Therefore, when I saw a grayish product (silver) I was not surprised. However, I was surprised by the white flash and the production of a white product, which were reminiscent of the classic combustion of magnesium demonstration. This led to some research and my conclusions that follow. Read through to the end and you will find a video of the demo.
The chemistry of the Berry dye found in McCormick's Color From Nature food colors is explored. This is part two of a three-part series in which the chemistry of McCormick's Color From Nature food colors is presented.
The lab was a success as I watched startled students produce the so-called barking dog sound as they combusted the hydrogen gas in their inverted test tubes.
I have used several different versions of the Silver Mirror or Tollen's Test lab. I am sharing the method that has proven to be the most reliable for me. The solutions should be made fresh, the directions must be followed closely and timing is very important. I like the fact that relatively small amounts of the chemicals are required, but as always you must be vigilant with safety precautions.
My IB seniors are just wrapping up our unit on electrochemistry and redox. This has always been a challenging topic within the IB curriculum. Admittedly, electrochemistry has not ever been my strong suit either, so this year I aimed to strengthen the unit with two additional demonstrations.
The chemistry of silver and the process in which silver becomes tarnished is explored. Take a new look at an old JCE Classroom Activity.
You can perform an orange to black chemistry demonstration using materials commonly found in stores. The reaction appears to be similar to the Old Nassau reaction, but uses greener reagents. This is a great demonstration to do around Halloween time.
In this Activity, students investigate the process of rusting by studying the oxidation of steel nails in a gel using supermarket chemicals. An indicator makes the presence of Fe3+ produced by the oxidation visible. Factors that accelerate or retard the rate of iron oxidation are studied.
In this Activity, students compare the combustion of different substances such as a glowing wooden toothpick and lit birthday candle in air, oxygen, exhaled breath, and carbon dioxide environments. The oxygen and carbon dioxide are generated from supermarket chemicals. This Activity can be used to explore the chemistry of oxygen and combustion.