Objectives

To demonstrate how goldenrod paper can be used as an acid/base indicator

Materials

• Goldenrod paper (true golden rod paper can be purchased online or at a science supply store)
• Small unlit birthday candle
• Two small plastic cups
• Cotton swabs
• Two small plastic cups
• Windex- or any ammonia based product
• Lemon juice or vinegar

Procedure

Place a piece of goldenrod paper on a table. Use the wax candle (not the wick end) to write a secret message on the paper (naughty or nice). Pour some of the Windex (ammonia-based) in the cup. Dip a cotton swab in the Windex and wipe it across the secret message. What happens? For an extended activity, dip a second cotton swab in the cup of lemon juice and wipe it across the message. See what happens now!

Conclusion

The Windex (ammonia-based) on the cotton swab is a base and causes the dye in the special goldenrod paper to change to red. As a result, the message will appear. For an immediate change from red/orange back to yellow, the lemon juice or vinegar, an acid, is used.