Flame Test Lab
Summary
In this lab, students were given many different substances to hold over a flame and were asked to observe the colors of the flame produced. This helped demonstrate the relationships of the flame colors and the certain atoms contained in compounds.
Pre-lab Questions
1) What is the difference between ground state and an excited state?
Ground state is the most stable state where all the electrons are in the lowest energy levels. On the other hand, an excited state is where the electrons are in an unstable arrangement, and will go back to their normal positions of lower energy.
2) What does the word "emit" mean?
The word "emit" means to "produce and discharge", especially in gas or radiation.
3) In this experiment, where are the atoms getting their excess energy from?
In this experiment, the atoms are getting their excess energy from the heat of the bunson burner's flame, where the electrons can reach an excited state.
4) Why do different atoms emit different colors of light?
Different atoms emit different colors of light because when an electron is in an excited state, it will fall back to their normal positions of lower energy, and then releases its previously absorbed energy. This causes different colors of light because the color depends on the differences of the higher energy and the lower energy.
Analysis Questions
2) What patterns do you notice in the groupings?
The substances that had a blue/green flame--CuCL2, Cu2SO4, and Cu(NO3)2-- all contained Cu, or copper. Also, NaCL and Na2CO3 both had an orange flame color and they both contain Na, or sodium.
3) Predict the flame color for a substance called strotium sulfate. Explain your reasoning.
I predict the flame color for a substance called strotium sulfate will be red. This is because one of the substances we tested for in the lab, SrCl2, also contained strotium, and it had a red flame color.
4) What evidence do you have that atoms of certain elements produce a flame of a specific color?
From the data table, you can see that CuCL2, Cu2SO4, and Cu(NO3)2 all had a blue/green colored flame. All the substances that had blue/green flames contained Cu, or copper. Also, two out of the three compounds that produced orange flames had Na, or sodium. In addition, metals in the compounds never produced more than one color, regardless of whether there are nonmetal ions.
5) Can a flame test be used to identify a metal atom in a compound? Why or why not? What about a nonmetal atom?
A flame test can be used to identify a metal atom in a compound because throughout the experiment, the color and metal were consistent. For example, compounds with copper in them only produced a blue/green flame and compounds with sodium in them only produced orange flames. Nonmetal atoms, however, cannot be identified by using a flame test. For example, chlorine was present in many different colored flames.
6) Identify the two unknowns. What are they and how do you know?
Unknown 1 is LiCl, or lithium chloride. We know this because the flame colors are the exact same; a dark magenta, and red with a little pink.
Unknown 2 is KCl, or potassium chloride. We know this because the flame colors are the exact same; lavender/light purple.
7) Copper oxide, CuO, is a black solid. It doesn't look at all like the element copper. What color flame would it produce?
Since CuO contains copper, we can infer that the color of the flame will be blue/green. From the data in our lab, the substances that contained copper all emmitted a blue/green flame, despite if the color of the substance itself was off.
In this lab, students were given many different substances to hold over a flame and were asked to observe the colors of the flame produced. This helped demonstrate the relationships of the flame colors and the certain atoms contained in compounds.
Pre-lab Questions
1) What is the difference between ground state and an excited state?
Ground state is the most stable state where all the electrons are in the lowest energy levels. On the other hand, an excited state is where the electrons are in an unstable arrangement, and will go back to their normal positions of lower energy.
2) What does the word "emit" mean?
The word "emit" means to "produce and discharge", especially in gas or radiation.
3) In this experiment, where are the atoms getting their excess energy from?
In this experiment, the atoms are getting their excess energy from the heat of the bunson burner's flame, where the electrons can reach an excited state.
4) Why do different atoms emit different colors of light?
Different atoms emit different colors of light because when an electron is in an excited state, it will fall back to their normal positions of lower energy, and then releases its previously absorbed energy. This causes different colors of light because the color depends on the differences of the higher energy and the lower energy.
Analysis Questions
2) What patterns do you notice in the groupings?
The substances that had a blue/green flame--CuCL2, Cu2SO4, and Cu(NO3)2-- all contained Cu, or copper. Also, NaCL and Na2CO3 both had an orange flame color and they both contain Na, or sodium.
3) Predict the flame color for a substance called strotium sulfate. Explain your reasoning.
I predict the flame color for a substance called strotium sulfate will be red. This is because one of the substances we tested for in the lab, SrCl2, also contained strotium, and it had a red flame color.
4) What evidence do you have that atoms of certain elements produce a flame of a specific color?
From the data table, you can see that CuCL2, Cu2SO4, and Cu(NO3)2 all had a blue/green colored flame. All the substances that had blue/green flames contained Cu, or copper. Also, two out of the three compounds that produced orange flames had Na, or sodium. In addition, metals in the compounds never produced more than one color, regardless of whether there are nonmetal ions.
5) Can a flame test be used to identify a metal atom in a compound? Why or why not? What about a nonmetal atom?
A flame test can be used to identify a metal atom in a compound because throughout the experiment, the color and metal were consistent. For example, compounds with copper in them only produced a blue/green flame and compounds with sodium in them only produced orange flames. Nonmetal atoms, however, cannot be identified by using a flame test. For example, chlorine was present in many different colored flames.
6) Identify the two unknowns. What are they and how do you know?
Unknown 1 is LiCl, or lithium chloride. We know this because the flame colors are the exact same; a dark magenta, and red with a little pink.
Unknown 2 is KCl, or potassium chloride. We know this because the flame colors are the exact same; lavender/light purple.
7) Copper oxide, CuO, is a black solid. It doesn't look at all like the element copper. What color flame would it produce?
Since CuO contains copper, we can infer that the color of the flame will be blue/green. From the data in our lab, the substances that contained copper all emmitted a blue/green flame, despite if the color of the substance itself was off.
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| Flame of CuCl2 |
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