Have you ever seen a metal ball shrink, or a rubber ball—once soft, flexible and bouncy—shatter upon impact? At a science assembly event at William H. Ziegler School on Tuesday, Nov. 13, students grade 4 through 8 were able to witness this firsthand.
Sponsored by The Franklin Institute, the science assembly event featured a “hot & cold” presentation demonstrating how temperature affects matter. Presenter David Henry Wrigley used extremely cold liquid nitrogen, with a boiling point of -320℉, to show that the different states of matter—solid, liquid and gas—can change form when placed in the right conditions.
David began by saying that matter—anything that has mass and takes up space—is made up of tiny particles called molecules, which are attracted to each other and can move past one another. The degree to which they move determines their state of matter: molecules that don’t move direction and simply vibrate in place make up a solid; molecules that slowly move past one another make up a liquid; and molecules that quickly move past one another make up a gas.
Students demonstrated this throughout the presentation by making small circles with their fists (“molecules”) and wiggling their arms back and forth at varying speeds. Each speed demonstrated a different state of matter. Students also volunteered to be “molecules” and/or scientists onstage.
David then explained that even humans are made up of molecules. The atmosphere is made up of 78 percent nitrogen and 21 percent oxygen, both gases. The oxygen, in particular, reacts to the broken down carbon compounds in our food, which produces carbon dioxide. Through the exchange of gases in our lungs, some of the oxygen is retained and we exhale 78 percent nitrogen, 15 to 18 percent oxygen, 4 to 5 percent carbon dioxide and smaller amounts of other gases.
Jayleene, a 7th grader at William H. Ziegler School, was surprised to learn this. “They’re are all around us,” Jayleene said about the molecules. “[They’re] in the environment and our bodies.”
David then went on to perform several experiments with the students demonstrating the different states of matter.
With a decorated pink balloon named BoBo filled with helium, David (with protective gloves on—as direct contact with liquid nitrogen can cause frostbite) began to rotate the balloon in a container filled with liquid nitrogen. As he continued to rotate the balloon, it began to shrink. According to David, the molecules in the balloon (which were once moving past each other at rapid speeds) began to slow down, causing them to get closer together and take up less space. Once he removed the balloon from the liquid nitrogen, however, it began to expand again. The molecules within it were re-exposed to room temperature, causing them to regain speed and consume more space.
In another experiment, David used a metal ball and a small board with a hole in it to demonstrate how temperature affects metal. With a few student volunteers, he was quickly able to show that the ball would not fit through the hole. After sitting it in liquid nitrogen for a few minutes, however, he was then able to successfully fit the ball through the hole. By applying the cold pressure of liquid nitrogen, the molecules in the ball moved ever so slightly, shrinking in size just enough so that the ball could fit through the hole.
As the metal ball sat in liquid nitrogen, David showed the students what the substance’s effect would be on a rubber ball. The presenter demonstrated the properties of the ball by bouncing it, saying that its molecules could bend, twist, compress and return to their original size. Once introduced to liquid nitrogen, however, the ball’s molecules behaved differently: they became rigid and stopped moving past one another, causing the ball to harden and shatter upon impact.
For many students, this was the standout part of the afternoon.
“My favorite part was when he put the ball into the [liquid] nitrogen and then when he took it out of it, he threw the ball to the floor and then it cracked,” said Mia, a 7th grader at William H. Ziegler School.
For Mia, specifically, she had never seen this before. “It was nice to experience something new,” she said.
David closed the presentation by saying that nitrogen is all around us, even in the air we breathe. You can take the nitrogen “home” with you and tell your friends about the active molecules moving around in your bodies and lungs.
The science assembly event was one of several held at PAEP’s STEAM After School sites this fall, all sponsored by The Franklin Institute. The topics change throughout the year, exposing students to a realm of subjects under the STEAM umbrella.