Ginny, Shenzhen College of International Education 深圳國際交流學院 Ginny Going back to school is one of the most unwilling events that take place all around the world after a pleasant winter holiday. However, I personally love the first day of school because I can meet my friends and attend all the intriguing curriculums again. A good example is chemistry practice class. Before we started the practice, all of us — including the teacher — grabbed a pair of goggles and put them on. Safety is always important in experiments, especially the ones that involve lighting a fire. (But you could juggle a few pairs of goggles like our teacher did, since they are not made of glass.) The first part of the experiment was a test for cations. We added a few drops of diluted sodium hydroxide or ammonia solution into different kinds of crystals, such as copper, zinc and aluminum, and observed. If precipitate is formed after the addition, then cations are presented. At the end of this experiment, we lit a fire to prepare for the heating of ammonium salt with sodium hydroxide. The teacher delivered two pieces of litmus paper to each group, and told us to put one at the opening of the test tube containing ammonium. I began to heat the test tube evenly above the fire. As the litmus paper turned red, an indescribable smell rushed out of the test tube — ammonia gas was given off. If you don’t know what kind of smell that is, well, we all have been to uncleaned public toilets, right? After the heating, we cleared our test tubes. The litmus paper shouldn’t be directly poured with other materials into the sink, or our teacher will “be arrested for throwing a student from the fifth floor.” The next part was flame tests. These are tests for metals that burn with unique-colored flames. I lit a fire again — but a much larger fire — to make the results more viewable. First our group tried some calcium solids. We put them on a wet twig and stuck it into the fire. A brick-red colored flame rose. Potassium produced a lilac flame that caused the members in my group a mild scream. But the most surprising color was the flame set by copper crystals. Blue copper crystals can create a blue-green flame! The small green flame ornamented the original red fire, making an obvious contrast. Going back to school is actually a quite happy time. | 