Activity

Invisible ink

Summary
Write a note in (nearly) invisible ink
Science content
Chemistry: States of Matter, Properties of Materials (K-7)
Chemistry: Chemical Changes (2, 7)
Science competencies (+ questioning + manipulation + others that are in every activity)
Planning/conducting: planning investigations (3 up)
Evaluating: inferring (3 up)
Lessons activity is in
Forensic science
Materials
  • saturated baking soda solution in a tub
  • Q-tips
  • card to write note on
  • grape juice/red cabbage juice in a tub
  • paintbrush
Procedure

Write your note in baking soda solution.
Allow to dry.
The note will be barely visible (though not invisible).

Paint grape juice over the note to make it visible.
(The grape juice turns a different colour when covering the basic baking soda solution).

Other idea for invisible ink:
lemon juice invisible until heated

Notes

As the juice is painted over it dissolves and smears the baking soda painting. Needs more troubleshooting.

Grades taught
Gr K
Gr 3
Gr 4