Lab

Summary

In this lab, students create a silver-plated test tube as a holiday ornament.

Grade Level

High school

Objectives

By the end of this lesson, students should be able to

• produce a silver-plated test tube using proper lab techniques.
• explain the process of reduction of silver nitrate.

Chemistry Topics

This lesson supports students’ understanding of

• Reduction

Time

Teacher Preparation: 45 minutes
Lesson: 50 minutes

Materials

• 50-mL beaker
• 0.1-M silver nitrate (AgNO₃)
• 15-M ammonium hydroxide (NH₄OH)
• 0.8-M potassium hydroxide (KOH)
• Test tube
• 0.5-M dextrose (C₆H₁₂O₆)
  
• Graduated cylinder
• Test tube stopper
• Safety goggles

Safety

• Always wear safety goggles when working with chemicals in a laboratory setting.
• When working with bases, if any solution gets on your skin, alert your teacher and thoroughly flush your skin with water immediately.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

• Encourage students to read through all procedures before beginning the lab. Timing is a big part of getting favorable results. 
• Cleanliness is essential to experiment success.  Rinse everything with tap water and then distilled water.

Downloads

• Teacher Guide.doc
• Teacher Guide.pdf
• Student Activity.doc 
• Student Activity.pdf

Submitted by
Andrew Ryan
Freedom High School
Freedom, Wisconsin

Thanks to
Flinn Scientific

For the Student

Lesson

Background

In this lab, a mirror will form on the inside of a test tube when a thin film of metallic silver deposits on the inner surface of the tube.  The silver metal is formed by the reduction of silver nitrate by an aldehyde (dextrose).  When the surface of the glass is clean and wet the silver will adhere to the glass, forming a mirror.

Purpose

To make a silver-plated test tube as a holiday ornament.

Materials

• 50-mL beaker
• 0.1-M silver nitrate (AgNO₃)
• 15-M ammonium hydroxide (NH₄OH)
• 0.8-M potassium hydroxide (KOH)
• Test tube
• 0.5-M dextrose (C₆H₁₂O₆)
  
• Graduated cylinder
• Test tube stopper
• Safety goggles

Procedure

Read all steps carefully before completing them.

Part 1

1. Obtain a 50-mL beaker an add 6 mL of silver nitrate (AgNO₃).
2. Add drops of concentrated ammonium hydroxide (NH₄OH) until a cloudy precipitate appears. Continue adding drops of the ammonium hydroxide until the precipitate disappears.
3. Add 3 mL of potassium hydroxide (KOH). A brown precipitate may form.
4. If a brown precipitate forms, add more drops of ammonium hydroxide until the brown precipitate disappears.

At this point you should have about 10 mL of clear liquid in a 50-mL beaker. (This contains your silver in the form of [Ag(NH₃)₂]⁺.) Set this aside and move onto part two.

Part 2

Obtain a clean test tube for silver plating.

Read this section completely before starting.  Quickness and accuracy is crucial for success.

1. Obtain 2 mL of dextrose in a graduated cylinder
2. Fill test tube for plating three-quarters full with hot water.
3. The next two steps need to be done in quick succession. Pour the hot water out of the test tube and pour 2 mL of dextrose into the hot test tube; swirl to coat evenly.
4. While the test tube is hot and the dextrose is covering the inside of the test tube, quickly pour the contents from pat 1 (the silver mixture) into the hot dextrose test tube. Stopper and immediately agitate the test tube. Use a gentle rolling/shaking motion.
5. A silver mirror should coat the inside of the test tube. Pour the contents of the test tube down the drain.
6. Gently rinse your test tube with 3 mL of distilled water.
7. Decorate with ribbons and give it to a loved one.

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