Flame Test Technicolor Atoms

Flame Test According to Bohr theory of the atom, electrons may occupy only specific energy levels. Electrons in atoms jump from their ground state to excited states by absorbing energy. Eventually these electrons fall back to their ground state, reemitting the absorbed energy in the form of light. Because each atom has a unique structure and arrangement of electrons, each atom emits a unique spectrum of light. This characteristic light is the basis for the chemical test known as a flame test. In this test, being placed within a flame excites the atoms. As they reemit the absorbed energy in the form of light, the color of the flame changes. For most metals, these changes are easily visible. However, even the presence of a tiny speck of another substance can interfere with the identification of the true color of a particular type of atom.

“Excited” Electrons

Procedures Put on safety goggles and a lab apron. Points will be deducted if at anytime during the lab your goggles are not on you face. Dip one side of a Q-tip into water, and then dip it into the first crystal sample. Place the coated Q-tip into the flame and observe any color changes in the flame. MAKE SURE NOT TO LEAVE THE Q-TIP IN FOR TOO LONG BECAUSE IT WILL START TO BURN. Write you observations in your data table under “color of flame.” Repeat steps 1-4 with all the 11 samples. Always be sure to use a clean Q-tip with each new sample and when the Q-tip starts to burn. Clean up by placing all used Q-tips into the trash and cleaning your lab table. Wash your hands before leaving class.

Analysis Questions Group the substance based on the flame color produced. What patterns do you notice in the grouping? Predict the flame color for a substance called strontium sulfate. Explain your reasoning. What evidence do you have the atoms of certain elements produce a flame of a specific color? Copper oxide, CuO, is a black solid. It does not look at all like the elemental copper. What color flame would it produce?

Purpose Flame tests provide evidence of the presence of certain atoms in compounds. Different metal atoms produce different-color flames when heated. Flame tests give some evidence that atoms are not destroyed when they combine to form compounds. Purpose of yesterday lab: To provide evidence for the presence of certain atoms within compounds.

Results

Conclusion Restate the purpose of the lab (1 sentence) The purpose of this laboratory was … Describe the use of the flame test and how it can help identify the presence of certain metal ions. (2 sentences) The flame test lab is a test which… State your results (2 sentences) In this lab it was determined that a _______ light showed _____… Concluding sentence It was concluded that the flame test…