The video above shows our group’s attempt to make hard candy using the principles of colligative properties.
The dominating concept in this experiment is boiling point elevation. The excessive amounts of glucose added to the mixture (in the form of table sugar and corn syrup) raised the boiling point of the mixture and made the melting of the candy-making process possible. If you want to learn more about the boiling point elevation involved in this experiment, check out the sample calculations in the boiling point elevation tutorial.
Though our group did not have access to a candy thermometer, we tested the temperature of the candy using the Cold Water Candy Test. We wanted our candy at soft crack stage, so we knew it had reached 270-290F, the stage in which candy threads dropped in water are slightly brittle. Calculations for this experiment can be found here (scroll down to the sample problem).