Lishan High School (Lab Sessions and Presentations)

Lishan High School

Aim: To determine the time taken for solution to turn blue

We were given 10 test tubes: A1~A5 & B1~B5. By mixing A1 with B1, A2 with B2, and so on, we can determine if the concentration of tube A affects the speed of reaction. Test tube A contains potassium iodate [KIO3] and tube B contains Sodium Bisulfite[NaHSO3], Sulfuric acid[H2SO4] and starch. By mixing the two test tubes, the iodate ions and bisulfite ions will react. This is the formula:  

IO3- + 3HSO3-I-  + 3SO42- + H+

When the HSO3- has completely reacted, there will be excess IO3- ions in the solution, which will further react with the I- :  
IO3- + 5I- + 6H+ 3I2 + 3H2O

The product, I2 then further reacts with the starch to form I2-Starch coordination complex, which causes the colour of liquid to turn blue:

I2 + Starch I2-Starch coordination complex

We had 4 presentations afterwards, first by Mr Tan, followed by Kang Zhe and 2 teams from Lishan High School. Mr Tan talked about the ISS projects in SST and the STEM approach in doing so. Kang Zhe gave a talk about spectroscopy and blackbody radiation. The first team from Lishan High School talked about harvesting energy from the air. The second team talked about how silkworms with titanium dioxide rich diet affects the silk quality

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