In the beginning of the unit, students will take stock of what they know about sugar. Usually we employ a graphic organizer called a KWL (what I know; what I want to know; and what I learned) chart. Here the teacher would solicit from students what they know. This would include whatever perceptions they have whether correct or incorrect. Then the class would suggest questions they have about sugar. The questions suggested here would likely include scientific questions about sugar; practical questions about where and how sugar is grown and could also extend to the nutritional value of sugar.
Doing this process with my students elicited some basic knowledge that one would expect: that sugar is something sweet; has a pleasant taste and is added to other foods. They were aware of the fact that there was white and brown sugar and that it grew as a plant. It was mentioned that sugar was in candy and it caused cavities. An argument almost ensued as one student said that sugar was "bad" because people got fat eating foods with a lot of sugar. Another student countered that sugar wasn't bad and that it wasn't sugar that caused a problem. We tabled the discussion for our research.
When we turned to what they wanted to know the questions ran the gamut from how sugar got its name to how it was made. Students wanted to know what "ingredients were in sugar." They also wanted to know about where it came from and what was it that made sugar sweet. Still others questioned how salt was like sugar and why it was white.
Their questions offered a suggestion as to how this unit could proceed. I would suggest that each question would be given to a student or pair of students so they could do some preliminary research. Children would do research about sugar to answer and verify what they think they know and want to know. If they find information that contradicts what they offered the KWL chart would be corrected. As they begin to build background knowledge the unit would then start considering the science of sugar. The last column on the chart of what I learned can be filled in as the unit progresses or if preferred after the unit is completed. I think that given this topic and the breath of information that I would like students to build the information on charts that would be hanging in class so they could readily see the growth of information and have it for easy reference.