They were given limited supplies of chemicals and very basic instructions that described how to produce the colour change used to time the reaction. During the reaction, the iodine produced reacts with thiosulfate ions, delaying the colour change. Once the thiosulfate ions are used up, the iodine reacts with starch in the solution to produce a distinctive blue-black colour very quickly.
The students needed to time 20 seconds, which they attempted to do by varying the mass of sodium thiosulfate. After a series of trials, they were ready to compete. To accurately measure their clocks, SeoYoung used a mass balance and light sensor connected to a data logger to record the entries. Tension grew as students mixed their solutions together, hoping their colour change would coincide with the final notes of the countdown music. Abhishek, in Year 12, enjoyed the competitive nature of the activity: “It was fun, and the fact we had to use the reaction as a timer made it more competitive. I had to concentrate when I was measuring the chemicals to make sure everything was perfect.” Head of Hue House Ms Gallagher struggled to contain her excitement as Hue participants and members of her form, 10V, competed.
The winners of the competition will be announced during assembly later in the term. For Chemistry Ambassador Tom Lee and Seo Young Jung, preparation for the Chemistry competition began weeks earlier, with careful trialing of the methodology and equipment.
Jodie Westwood, Head of Chemistry