Experiments with Secret Messages

• Critical thinking
• Problem-solving

Experiment 1: 

• Paper 
• Brush 
• Glass cleaner spray 
• Phenolphthalein alcoholic solution

Experiment 2: 

• Scissors 
• Pens/markers of various colours 
• Alcohol 
• Coffee filter paper 
• Glass (cup/glass to facilitate the monitoring of the experiment)

Experiment 1: Secret Message

• Write a message on a piece of paper using the brush and the phenolphthalein alcoholic solution 
• Let it dry for a few minutes 
• You can now reveal your message using the glass cleaner! 

Experiment 2: Colour Race

• Use scissors and cut strips of filter paper. For each pen used, a rectangle should be enough. 
• Now, at a distance of approximately 2 cm from the base, draw a circle with the chosen color pen and paint the entire interior.
• Attach the end of the paper farthest from the ball drawn on a support. For this, you can use tape and attach it to a pencil. 
• Add alcohol to the glass, not too much as it should just touch the edge of the paper next to the pen mark. 
• Place the paper in the cup so that it is vertical. The pencil that supports it must rest on the edges. 
• Wait between 10 and 15 minutes for the alcohol to rise through the filter paper. After that, remove the papers and let them dry. 

When alcohol passes through the pen mark, it interacts with the color components and conducts them through the paper. Thus, the different pigments will be separated by contact with alcohol.

Through this experiment, it is possible to know which colors were mixed to create the color of the pen!

Explanation for Experiment 1:

The message initially appears blank on the sheet of paper. The alcoholic solution of phenolphthalein is an acid-base indicator and in the presence of bases, it acquires a crimson color. The message was written with phenolphthalein which remains colorless in the presence of acidic and neutral solutions. When sprayed with a basic solution (window cleaner) it acquires the crimson color, characteristic of this indicator, thus revealing the message. 

Explanation for Experiment 2: 

Chromatography is a type of process for separating mixtures. The filter paper is the stationary phase and the alcohol is the mobile phase that drags the components of the mixture when passing through the stationary phase. In this process, the greater the interaction with the alcohol, the faster the pigment will move with the passage of the solvent. The constituents of the material, because they have different properties, will interact with the mobile phase in different ways, which can be noticed by the different drag times in the stationary phase.