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## Activity: Flame Test

Days Needed 1.5 Days

### Objective

Students will discover first hand how different elements emit different specific wavelengths of light energy when burned, and that these can be identified when the light is separated with a prism.

### Science and Math Standards

 NCTM NSES Content Standard 2: - Mathematics as Communication Content Standard B: - Abilities necessary to do scientific inquiry - Understandings about scientific inquiry Content Standard 4: - Mathematics as Connections Content Standard C: - Structure of Atoms - Interactions of energy and matter Content Standard 8: Geometry from an algebraic perspective Content Standard G: - Nature of Scientific Knowledge - Historical Perspectives

### Prequisites

Math Students should have had some Pre-Algebra, especially in the areas of manipulation of formulas and pattern recognition.
Science Students should have had an introduction to the electromagnetic spectrum, the concept of a spectrum and how atoms emit light energy.

### Introduction

Recalling the characteristics of both atoms and light, the flame test is a great way to physically demonstrate some of the more abstract ideas discussed in the background sections on Atoms and Light Energy and Spectroscopy.

### Exploration

The students will work in lab groups of three to four students to construct meaning on the causes of various light emissions from the following 0.5M chemical solutions: LiCl, NaCl, CuCl, BaCl, CsCl, and CaCl. To prepare for the Flame Test, each 0.5M solution should be placed in a test tube by itself. Each of the six test tubes should then be placed at the various laboratory stations 1 through 6. The students will rotate to each station to test the solution.

Materials

• 7 test tubes
• test tube rack
• platinum wire or wood splints
• laboratory burner
• goggles
• apron
• 0.5M solutions of LiCl, NaCl, CuCl, BaCl, CsCl and CaCl, and 1M of HCl.

Hand out the student worksheet. Have the students answer the thought questions at the end of Part I in groups, but on paper. They should be utilized to facilitate a meaningful discussion on light emission. Afterwards, the students should complete the questions in Part II individually. They may be assigned for homework if there is not enough class time.

• Student Worksheet

### Evaluation

Formative assessment and observation should be evident throughout the lesson. The worksheet, final questions during closure or a future quiz may serve as summative assessment.

### Closure

Have students take three minutes to write in their own words why different elements produce flames of different colors when burned. How is this quality useful in astronomy?

### Reference URL

Flame Test
http://www.creative-chemistry.org.uk/activities/flametests.htm

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