Name: ______Date: ______Period: ______

Light Spectra and Flame Test

Background:

Electrons in an atom can jump up or down from one energy level to another by absorbing or releasing energy. This energy is often released in the form of light of a particular color. Most of the time the color that is observed is actually a blend of several colors. When viewed through a diffraction grating or a spectroscope, the separate colors can be observed as lines. These colors correspond to the energy released as electrons jump down to a lower energy level. Atoms that use more energy levels produce more lines of color.

The particular pattern of colored lines of light is unique for every element and is called a spectrum. In this way, elements in stars can be identified by looking at the lines of color in the star’s light.

Part 1: Line spectra of Some gas elements

The elements we will observe first will be gases. For each gas, use the spectroscope to observe the spectrum of colored lines. Draw the pattern of colored lines in the space as accurately as you can.

Element Name: ______

Violet Blue Green Yellow Orange Red

Element Name: ______

Violet Blue Green Yellow Orange Red

Element Name: ______

Violet Blue Green Yellow Orange Red

Element Name: ______

Violet Blue Green Yellow Orange Red

Element Name: ______

Violet Blue Green Yellow Orange Red

Element Name: ______

Violet Blue Green Yellow Orange Red

Part 2: Flame test of identification of metals

The color of light produced is a characteristic property of the element. Many metals can produce beautiful colors when energy is added in the form of heat. This property is useful in the creation of firework displays.

Materials:

Goggles & Apron Burner

200mL of distilled water Small Pan

7 Q-Tips Chemical Sample (Pea size amount)

Procedure:

***Goggles & apron on and light the burner only when you need it.***

1.  Retrieve a pea-size sample of the copper powder.

2.  Dip the q-tip in to the water then into the copper sample so that some of the copper crystals stick to the q-tip.

3.  Place the q-tip into the flame so that the crystals are fully in the flame (do not place to much of the q-tip in the flame or it will melt and ruin your experiment.)

4.  Record the observed color of the flame in the table below.

5.  Dispose of the extra chemical and cool q-tip in the trashcan.

6.  Clean the pan and repeat the steps for barium, strontium, calcium, sodium, potassium, and lithium.

Data Table:

Chemical / Color Observed
Copper
Barium
Strontium
Calcium
Sodium
Potassium
Lithium

7.  Obtain a sample of an unknown compound. It will contain one of the metals you observed.

a.  Record the number of the compound you chose here: ______

b.  Repeat the experiment with your unknown compound.

i. What color did you observe? ______

ii.  Which chemical is your unknown? ______