What: Sixth-grade science students at a Roseville elementary school will have a bit of scientific sleuthing to do in Monday's class, but they'll have the crackerjack help of UC Davis chancellor and biologist Larry Vanderhoef. In town for a get-acquainted meeting with Roseville Mayor Mel Hamel -- who happens to be principal of Spanger Elementary School -- Vanderhoef will drop by sixth-grade science teacher Debbie Lopes' class to help students identify a "mystery" powder Lopes will say was discovered on the school's playground. The chancellor and the students will mix various powders into liquid to determine the mystery powder's identity, learning scientific methods in the process. When: Monday, Oct. 9, at 9:30 a.m. Where: Spanger Elementary School in Roseville, 669 Shasta St. Directions: From Sacramento, take I-80 east to the Atlantic/Eureka St. exit. Turn left on Atlantic and right on Yosemite at the light. At the second stop sign, go straight (Yosemite turns into Shasta). The school is a half block down, on the right.