Flame Tests for Metals

Flame Tests for Metals

17th October 2015

Lab Report 4: Flame tests for Metals

This experiment is about to observe the color different element produce when being heated.. The principle of this is when elements were heated to a high temperature, some of their electrons are excited to higher energy level. When these electrons fall back to lower energy levels, they release excess energy in package of light called photons, light quanta. Within the result of the experiment, we can identify metallic ions by using flame tests, because when elements get heated, they emits a characteristic pattern of light energies.

Procedure

In this experiment, we used the following materials:  8small test tubes, test-tube rack, paper towel, scoopulas, 50-mL beaker, platinum wire or nichrome wire loop, gas burner, cobalt-blue glass and as always, the goggles. We used these samples: KNO3, Ca(NO3)2, Sr(NO3)2, LiNO3, Cu(NO3)2, NaNO3, Ba(NO3)2, 6M HCl and an unknown salt. This experiment needed us to be very careful, because the materials were harmful to our body, so we must avoid skin contact. First, we used scoopulas to get a little of each samples and put each of them into a small test tube. Then I poured out 15 mL of 6m HCl into a 100 mL beaker, turned on the gas burner, then dipped the wire loop into the HCl and heated it with the hot flame. And kept doing it until their is no color produced when put the fire loop into the flame. And made that in mind, do not touch the end of the wired loop after heated , it was extremely hot , it could cause burned. When the wired loop were bented, I used my hand to bend the wire after it cooled down. After that, I used the heated wire loop to dip some salt from the test tube and burned it on the gas burner. A special color of flame would appear, then recorded that color. After that, I cleaned the wire loop by dipping HCl and burned it on the gas burner, then repeated this procedure for multiple times until there was no color comes from the wire. Then I tested another sample with the same procedure except sodium Na+ and potassium K+. For these two samples, after the normal procedure of recording their color, took a cobalt glass and put it in front of your eyes and observed them again, recorded the color I saw through the cobalt glass.  Cobalt glass was a special glass made of cobalt  which will filtrate the color of yellow. At the end, we tested an unknown salt. After these,  we carefully dumped the sample into the drains.

Observation

Watching The color different samples produce was such an enjoyable experience. The burning of the Sodium Na+ produce bright yellow flame; potassium K+ produced pink flame; calcium Ca2+ produced deep orange flame; barium Ba2+ produced bright green flame; strontium Sr2+ produced red flame; lithium Li+ produced rose red flame; copper Cu2+ produced fluorescent green flame. Though the cobalt glass, I saw sodium produced light white flame and potassium K+ produced purple flame.  It was just so beautiful!! Here is the picture of the flame.