Seeing Through Paper

Concept: The hexane causes the paper to turn from opaque to translucent, allowing light to pass through.

Materials:

Directions:

1. Write a message on the index card.

2. Place card in the envelope.

3. Seal the envelope shut.

4. Place the envelope on the pie plate.

5. Using the eyedropper put some hexane on top of the envelope until the writing becomes visible.

6. Show the envelope to the students, have them read your message.

Introduction:

Have you ever had to take a sealed envelope from your teacher and bring it to another teacher? Weren't you wondering what was in the envelope? But you know that if you opened it you would get into trouble. So I came up with a way that I could read the letter without having to open the letter. Now I can secretly know what message I am taking to a teacher. Here let me show you how I do it.

Explanation:

First a review of the transmission of light through various objects:
Transparent - clear, all light shines through.
Translucent - some light shines through although not clearly. Fuzzy appearance.
Opaque - no light shines through the object.

What is the property of paper? Opaque.
Paper (index cards) has water in it. The water inside the paper helps to make the paper opaque. Water is polar and hexane is non-polar. Water has both positive and negative molecules. Hexane has no charge. Alike properties mix, while unlike properties will not mix. Therefore when hexane is added to the paper (which is made up of water and cellulose) the two substances do not mix, so it makes the envelope translucent (you are able to see through it). This is why you can see what is written on the paper through the envelope.

Safety Precautions:

Waste disposal:

Reference: Unknown