BENNINGTON — Setting things on fire isn't usually part of science class.
But for fifth-grade students at Molly Stark Elementary School Wednesday, a presentation by the Traveling Programs department of the Museum of Science in Boston brought fire into science. That was the final experiment in a presentation called States of Matter, led by Brendan Cole, an education associate in the Traveling Programs department.
Cole began by asking the about 80 students to identify states of matter.
"Gas," one student said.
"Exactly," Cole said. He told everyone to take a deep breath. "We all just breathed in and breathed out some of different gases," he said.
Liquids have a certain size and volume, but they also take the shape of their container, while solids don't change shape or size — "unless something pretty dramatic happens," Cole said.
Cole demonstrated multiple ways of changing the state of matter, from solid to liquid and back to solid. He started by making solid metal liquid, through adding energy in the form of heat.
"We're going to use some water," Cole said, gesturing to a beaker on the table. "This water is warm, but it's not hot."
Most metals don't melt until they hit very high temperatures, he said. But they'll try to melt a mini metal object called Arnold, shaped like a robot, in the water.
"Arnold is melting," Cole said, as Arnold became liquid metal in seconds. The liquid has size, not shape. "That means Arnold has definitely melted."
Besides states of matter, Cole did another presentation Wednesday for fourth-graders on sound, called Now Hear This. The presentations were funded through a grant of $1,510, provided by the museum's Traveling Programs department.
To change the state of matter, it's just a matter of changing the temperature, Cole said. And, there's a mystery substance to bring Arnold back to solid, he said, referring to a large silver canister on his display table. As he opened the canister, a cloudy, gas-like substance escaped. Cole asked for visual observations.
"Smoky," one student said. "Foggy," another said.
Cole lowered his microphone to the side of the container, so students could hear what was happening.
"It sounds like someone's breathing," one girl said. Cole asked students to guess how hot the substance — a liquid — was.
Estimates ranged from 90 degrees to minus 129 degrees. The final temperature? Just about minus 312 degrees.
"Our liquid here is a liquid," he said. "Except is a liquid at negative 312 degrees Fahrenheit. With that information, Cole asked the students if they knew what the substance was.
"Nitrogen," one boy said.
"Yeah," Cole said. "Our liquid here is indeed known as liquid nitrogen." Most of the air around us isn't made of oxygen, but nitrogen, he said.
When a liquid turns into a gas, it's condensation — the same process when water becomes a liquid on the outside of the cold water bottle.
On a projector, Cole displays a chart of the different states of matter, with arrows signifying the changes in states."Does anyone see a hole in my chart?" he asked.
"The liquid to the solid," one girl replied. Just like melting, boiling from a liquid to a gas, or condensing from a gas to a liquid, matter should be able to go from a liquid to a solid, Cole said. To test that, they can use the now-liquid Arnold, he said.
"We're going to cool Arnold down," he said, pouring liquid nitrogen into a beaker that contained the liquid fragments of Arnold.
The different states of matter all look different under a microscope or magnifying glass. If that's true, knowing about matter would just be about memorizing their differences.
But that's not the case.
"Science isn't about memorizing things," Cole said. "It's about understanding things."
In the case of matter, he said, if you zoom in to a billionth of an inch across, you'd find that steam, water and ice are all made of the same molecules, moving in different ways.
"When we say something is a low temperature, we mean that its molecules don't have a lot of energy," Cole said. At low temperatures, molecules move slowly, and get faster as they get hotter. States of matter are just different amounts of energy molecules can have, he said.
Even water, heated high enough, can set paper on fire, he said.
"Setting something on fire is a little bit like changing something's state of matter," Cole said. Changing a state of matter is all about changing a substance's temperature — and it doesn't matter how you do that, he said.
He held a small square of paper with a set of tongs in front of a narrow hose, where steam generated from a beaker full of boiling water escaped.
The paper immediately burst into flames, to gasps from the audience.
Setting something on fire is different in a key way from changing the state of matter.
"When you set something on fire, you can't really go back anymore," Cole said. "Fire changes what something is."
Cole's presentations tie in with Next Generation Science Standards, which are used at Molly Stark. The Traveling Programs department of the museum has evolved to connect more with current standards — but science is important for other reasons, too, Cole said.
"It's important to look for evidence wherever you are," he said. "And it's fun, too."
Patricia LeBoeuf can be reached at firstname.lastname@example.org, at @BAN_pleboeuf on Twitter and 802-447-7567, ext. 118.