Basically Acidic Ink
Students hypothesize whether vinegar and ammonia-based glass cleaner are acids or bases. They create designs on index cards using these substances as invisible inks. After the index cards have dried, they apply red cabbage juice as an indicator to reveal the designs.
Students make invisible ink as they learn about acids and bases.Copyright 2010 Rachel Howser, GK-12 Program, University of Houston
Acid/base chemistry includes concepts applied across many engineering disciplines. Engineers use their knowledge of acids and bases to complete tasks such as designing non-corrosive infrastructure, batteries, chemical fertilizers and food preservation methods. Writing in an invisible ink that can be read using an acid/base indicator was commonly used by engineers, inventors and military leaders during the American Revolutionary War to communicate secret messages. Acid rain is a worldwide environmental problem that has been addressed by environmental engineers. Acid rain can alter the pH of water and soil and have negative effects on plants and animals. Environmental engineers conduct studies to evaluate the significance of environmental hazards, advise on treatment and containment, and help to develop regulations to improve or prevent polluting conditions.
After this activity, students should be able to:
- Hypothesize whether a liquid is an acid or base.
- Identify whether a liquid is an acid or base based on its color interaction with cabbage juice.
- Explain how acids and bases were used during the American Revolution to send spy letters.
- Describe how engineers use acids and bases.