Science Experiment

We all remember those teachers and professors who tried their best to make the class more interesting, using their interesting ideas and creativity. When learning is associated with something interesting, the things that we learn seem to stay in our heads forever, and that's what learning is about, right? Not to learn something and just to forget it after getting a good grade, but the knowledge to last longer, even forever.
Christine is a professor in one primary school. She teaches chemistry and she always likes to be well prepared for her classes, to keep the students' attention, and teach them many things. Today, Christine has a task to make a one really interesting experiment, together with her students.
However, before the class, she needs to prepare herself for that experiment. And even though Christine is a well-organized person, there is one big problem in front of her. Namely, the test tubes that should be given to the students are lost. Christine doesn't know where could they be and without them, she won't be able to complete the class successfully.