======Optical Activity of Sugar======


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**Alternative titles:** Rotation of Polarized Light by Sugar Solution
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====Summary====                   
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====Procedure====  
  - Cut two square holes in each cardboard sheet, spaced evenly apart.  
  - Tape polaroid films over the holes, ensuring one sheet has the polarizing direction at 90° to the other.  
  - Dissolve as much sugar as possible in 200 mL water in one beaker, heating to make a concentrated syrup. Leave the other beaker with plain water.  
  - Place one polaroid sheet on the overhead projector and set the beakers on top, each over one of the polarized light squares.  
  - Observe both solutions as light passes through.  
  - Place the second polaroid sheet above the beakers aligned with the first sheet at 90°.  
  - Observe that light only passes through the sugar solution, showing optical rotation.



====Links==== 
Optical Rotation Demonstration Polaroid and Glucose - Farnborough Chemistry: 
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📄 Optical activity of sugar (Demonstration 17, page 36) - Dr Magdalena Wajrak and Mr Tim Harrison: [[https://www.ecu.edu.au/__data/assets/pdf_file/0003/910443/Chemical_Demonstration_Booklet_Interactive_Final_14.2.21.pdf]]\\


====Variations====
  * Use glucose or fructose instead of sucrose and compare the degree of rotation.  
  * Try different concentrations of sugar to see how the brightness changes.  
  * Replace the overhead projector with a laser pointer and polarizing lenses for a smaller-scale version.



====Safety Precautions====
  * Handle the hot plate carefully to avoid burns.  
  * Prevent sugar solution from boiling over onto the hot plate.  
  * Allow hot sugar solution to cool before disposal.  
  * Wear safety glasses to protect against splashes.




====Questions to Consider====
  * Why does light pass through the sugar solution but not through plain water? (Because sugar is optically active and rotates polarized light, while water is not optically active.)  
  * What property of sugar molecules makes them optically active? (Their chirality – sugar molecules lack symmetry and exist in enantiomeric forms.)  
  * How would the demonstration change if a racemic mixture of sugar is used? (There would be no net rotation of polarized light, so no light would pass through.)  
  * What happens if you increase the concentration of the sugar solution? (The rotation of light increases, making the transmitted light brighter or more visible.)