Scientist leaves his mark on students
BY JENNIFER AMATO Staff Writer

ERIC SUCAR staff Mark Tripp describes a crime scene investigation technique during the "Crime Scene Science" assembly held at Judd Elementary School in North Brunswick on Friday.

NORTH BRUNSWICK - Mark Tripp had a student dip her finger into pencil shavings. He pressed her thumb onto a white latex balloon, and then inflated it for everyone to see.

"Look how clear that is," he said to the group of preschoolers through secondgraders in attendance.

As part of the "Crime Scene Science" assembly held by the Mobile Education representative at Judd Elementary School on Friday, Tripp spoke about how fingerprints are detected during investigations. The former high school physics and chemistry teacher said that in 500 A.D., the Chinese discovered that no two fingerprints are alike. He said the rest of the world caught onmuch later, with the first crime in London being solved by a fingerprint in which the crime never happened and the detective never lived - he was referring to Sherlock Holmes.

Tripp demonstrated the difficulty of finding fingerprints by having one student choose a tile letter froma felt bag and having another student use amagnifying glass to figure out where the print was left. Although the student couldn't figure out where the marking was, Tripp used an ultraviolet light to show a message saying "pick me" written on one of the tiles; he used sun block, which is visible in UV light.

"Interestingly enough,we are using light a lot now to find things we wouldn't normally find," he said.

Tripp also showed the students a chemical containing little crystals that have holes like a sponge. He said that when a liquid is added, those crystals swell, forming a puttylike casting. He said that in forensics, the substance can be used to lift fingerprints or tracks.

"The purpose of forensic science is not to put people in jail, but the purpose of forensic science is to keep people out of jail," Tripp said. "We've got to be careful. We can find that print, but we've got to make sure [it's correct]."

In addition, Tripp said that "chemistry is important in finding things that we don't know what it is." In one experiment, he wrote on a girl's shirt with magic disappearing ink - down her sleeves, on the front of the shirt and then on the back. He explained that some chemicals disappear in the presence of another chemical, which is called a chemical indicator. He said the ink would stay blue until it comes in contact with carbon dioxide, which is in the air.

Another experiment to demonstrate chemical indication used a jar of clear liquid. Phenolphthalein, which was the main component of Ex-Lax until 1998, turns purple in the presence of a base such as ammonia. Starch, when added to iodine, turns blue. Vitamin C plus two drops of sugar will turn the blue liquid clear again.

"Chemicals help usmake something unknown, known," he said.

After the experiments were concluded, Tripp challenged the students to find elements of chemistry at home. He said powder or syrup used to make chocolate milk, Kool-Aid or Crystal Light and toasting bread are all simple examples.

Tripp performed a similar assembly afterward for the third- through fifth-graders. The program was sponsored by the Judd Parent-Teacher Organization.