Science Buddies: "Ask an Expert"

I know that I have already asked this question but I didn't seem to get a reply to my previous one asked.

I'm currently planning my Rainbow Fire experiment (aka Flame Tests) and I am having trouble with coming up with a Problem. What is there to find out about when doing the flame tests?

I have been given some questions (from a previous Expert) to think about such as: "During a flame test, why do different metals emit different colors of light when burned?" or "During a flame test, what characteristics about the metal salts causes the color to change?" I agreed that these are good examples of what my Problem should be, but I am not sure how doing the experiment will answer these questions!

Please help me! I have read the background information of the Rainbow Fire experiment but I still can't seem to come up with a Problem and a Hypothesis for my project

I hope this explains my situation, and I hope someone will help me come up with an idea.

Thank you!

P.S. Isn't boric acid a non-metal? Can't only metals be used in flame tests???

Hi CheesyPandas15,

I'm sorry that you haven't been getting the answers you have been seeking. That sounds frustrating! I don't know that I have all of the answers, but I will do my best to help you.

If I understand you correctly, you are trying to figure out what your question and hypothesis should be for the Rainbow Fire project. If that isn't what you need help with, please let me know what other questions you have. Often times people use "problem" and "question" to refer to the same thing in a science fair project.

Flame tests reveal the energy associated with electronic transitions in certain atoms. You are going to burn different chemical compounds and observe their colors. You will be collecting data about the color of the flames, so your question and hypothesis need to somehow involve relate the colors of flames to the compounds you are testing. The question you are trying to answer is, "Do copper sulfate, sodium chloride, strontium chloride, and boric acid create different colors when burned?"

Your hypothesis could be as simple as a "yes" or "no". For example, "If I burn copper sulfate, sodium chloride, strontium chloride, and boric acid, then, yes, the flames of each compound will have different colors". Depending on how much chemistry you know, you could also predict what colors each compound would make. This would lead to a more sophisticated hypothesis, along the lines of "If I burn copper sulfate, then I will see a ____ colored flame. If I burn sodium chloride, then I will see a ____ colored flame. If I burn strontium chloride, then I will see a ___ colored flame. If I burn boric acid, then I will see a ___ colored flame." You would replace the ____ with the name of the color you expect to see.

The experiment itself doesn't tell you *why* the colors are different. It only shows you that the flames are, in fact, different colors for these different compounds. The questions the previous expert gave you are good questions to consider when you are writing up your analysis and conclusion, but they are not the question that you are testing during this experiment.

With regards to boric acid: All of the chemical you will be testing are compounds, not metals (copper sulfate, strontium chloride, sodium chloride, boric acid). The first three are salts; boric acid is a weak acid that you will use in crystalline form. In all of these cases, the flame test reveals electronic transitions associated with only one of the ions in the compound: copper ions, strontium ions, sodium ions, and boron ions. So, no, flame tests are not restricted to the atoms/ions of metallic elements.