Mystery Liquids

If you have already allowed children to experience chemical reactions, they will be sure to enjoy figuring out which liquids these are.  Now this experiment would go nicely with a CSI unit, if you tell children that these substances were found at a crime scene.  Then tell them that they have to figure out which substances were left at the crime scene.

Now, for the practical matters of this experiment.  First, I gathered five clear containers for each group and picked five mostly clear liquids.  You can use whichever liquids you would like, but I chose

*water

*vinegar,  

*very watered down dish soap,

*Sprite, and

*rubbing alcohol.  

I colored every substance with food coloring except for the Sprite to make everything more mysterious.  Also, just an FYI:  I watered down the dish soap to the point where bubbles were almost undetectable, so it would be harder to figure out.  I gave students small plastic spoons like the taste test spoons at an ice cream store to dip out the liquids.  I also gave them wax paper because the surface tension of the water on wax paper is so evident compared to other liquids.  Further, if they have a sheet of wax paper as opposed to a plate they waste less. Just have paper towels readily available.

Before I let the students have the materials, I made them tell what they could do to each substance to test it before they received the liquids.  These are some of the things they told me.

1. We can smell them.
2. We can look at them.
3. We can touch them.
4. We can taste them.  (at which point, I say absolutely not :))
5. We can look at our old notes and test them with pH strips to see if the results match.
6. We can do chemical reaction experiments.
7. We can compare them to the substances that are available ( I had some liquids available).

During experimentation, I had several things available in extra supply for experimentation:

• extra solids available in small cups
• extra liquids available in small cups
• pH strips (I dispensed as needed)
• cabbage juice (I dispensed as needed)

(these were set up similar to the chemical reactions lesson I already shared)

I left time at the end of our class for the students to discuss which liquids they were and to support their conclusions.  Most students were able to figure out all of the liquids except the water.  Some students asked me if I had duplicated any of the liquids, and I did not.  However, mwah ha ha, mwah ha ha (evil laughter), I did think about having two jars filled with water of different colors and having them figure this out.