Who killed Juan and How?
Maria Valencia
In the case of Juan Tapia, it was difficult to determine the cause of death. To refresh out
memory, Juan was a male around 15-16 years of age found dead on November 20,2012 at 8:10
a.m. Juan had no blood or obvious skin abrasions. Many forensic test were used to try to
determine the cause of death.
Ionic bonds are different than covalent bonds; we used these two types of bonds to help
us determine the cause of death. Covalent compounds electrons share electrons, as for Ionic
compounds it's a give and take of electrons. We performed two different types of Ionic bond
experiments. We tested to see if Juan was poisoned by Cyanide, to perform this test we tested his
saliva with Hydrogen Cyanide and Silver Chloride. To summarize the results of that specific test,
Juan was not poisoned by cyanide; however he had traces of it in his body.
To further on ways Juan could of died, we tested Juan's stomach contents, along
with other liquids that could have poisoned him. We tested this by finding which liquid was most
polar. Then we boiled each individual compound, the results were then compared to Juan's
boiling point. Water ( H20)boiled at 93°C , Ethylene Glycol (C2H602) at 103°C, and Isopropynol
at 78°C (C3H80). An intermolecular force is a attraction between molecules. When something is
polar, it creates a intermolecular force. Polar things have high melting points, leading to Juan's
stomach boiled at 102°C. Through evidence this leads to, Juan was poisoned by Ethylene Glycol.
Now that we know how Juan was killed, we needed to test who left the clue note, it could
lead to the murderer. To test the ink from the threat note, we compared the faculties different ink
to the ink used in the clue note. Each pen sampled a dot on the base line of the strip paper. It was
then submerged into the alcohol. The ink bleed a line, and each pen was compared to the clue
note line. The reason the ink bleeds is because, the ink is made of polar and non polar
molecules. The polar molecules are attracted to the polar water. The non polar are attracted to the
alcohol. The ink results show that Mr. Smith, the physics teacher's pen was used to write the
clue note.
The second test we performed was, who's fingerprint was on the beaker which was a covalent
test. Testing the fingerprint on the clue note was a ionic test. We used UV light to see who's
fingerprint was on the paper, this was the ionic test. Oils are nonpolar covalent molecules that are
left by your fingers. The oil from your fingers get absorbed in the paper, dusting wouldn't make
the fingerprint any more visible. This is where we use the salt from our fingers, to see the
fingerprint under a UV light. The salt from our finger does not get absorbed like oil, it stays on
the surface and in the cresses of our fingers, the UV light is just a tool to make the fingerprint
more visible. In the conclusion on the fingerprint lab, Mr. Smith the physics teacher's prints were
on the pen that wrote the clue note.
To conclude this report, Juan Tapia was killed through Ethylene Glycol poisoning. A clue
note was left behind, in which Mr. Smith's prints were found on. The pen that was used to write
the clue note also belonged to Mr. Smith.