By Jennifer Mulson jen.mulson@gazette.com -10 a.m.-3 p.m. Saturday, Barnes Science Center, Palmer Hall and Olin Hall of Science, 1040 N. Nevada Ave., Colorado College, free; info@coolscience.org, coolscience.org. Stop and have a marshmallow at the Palmer High School Chemistry Club's table at the Big Cool Science Festival. Yes, it might be rock hard - it's been immersed in liquid nitrogen, after all.