Practical work is often considered to be a highlight of science classes for students. However, there are few opportunities for students to engage in an investigation which is situated in a real world problem and students are required to contribute their own ideas to the design and conduct of an experiment. This paper reports on a Scientists in Schools (SiS) partnership between teachers at Leeming Senior High School and scientists at Curtin University. A low cost experiment is described that can be adapted for many educational settings. Students' reports of the practical work have been used to illustrate the paper which documents both the teachers' and scientists' positive perceptions of the SiS experience. (Contains 1 table and 5 figures.)