Sugar is an interesting ingredient. It behaves in different ways depending on how hot you cook it to begin with. Cook it too a low temperature (say below 240F), and it will stay liquid when cooled. Cooking it to between 240-270 or so will yield various states of chewy sugar--thicker and stickier the higher you cook it. Once you reach the 270s to about 305F, it will cool to varying degrees of "hard," from chewy hard to lollipop hard. For more information about the stages of sugar, see my Stages of Sugar chart.