CMS science teacher blows up pumpkins for educational purposes |

CMS science teacher blows up pumpkins for educational purposes

Ben McCanna

On Friday morning, Norm Yoast addressed his eighth-grade science class by asking students to don safety goggles.

Yoast stood at the head of the class. Directly in front of him lay a pumpkin on a pedestal.

"There are two types of energy — kinetic energy and potential energy," Yoast said. "Kinetic energy is anything moving.

"We're going to create some of that today."

Yoast then asked a student to kill the lights.

In sudden darkness, Yoast stepped toward the pedestal, flicked a butane lighter and blew up the pumpkin.

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For five years, Yoast, an eighth-grade science teacher at Craig Middle School, has been blowing up pumpkins to celebrate Halloween. An additional benefit to the unorthodox experiment is that it teaches principles of science.

Yoast ignited three pumpkins Friday.

He said the purpose of the experiment is to get students excited about chemistry.

"Chemistry is our biggest hands-on (unit)," he said. "We have about a 12-week chemistry unit where they'll have at least one lab per week."

The materials used in the teacher's lesson are a pumpkin, carving knife, water, some calcium carbide and a lighter.

Yoast said that after he hollows out a pumpkin, he scores a Jack 'O' Lantern pattern on the pumpkin's skin.

"We score the front of the pumpkin to make sure it blows out that way and not back at me," he said. "If it blows at me, that's bad." Yoast also cuts a small hole in the back of the pumpkin, just large enough to accommodate a lighter.

Next, Yoast said he pours water and calcium carbide into the hollow pumpkin.

"This is a chemical called calcium carbide," Yoast said to his class. "Calcium carbide is calcium carbon. It's pretty plain looking. It's just this grayish black rock. There's nothing to it. But, when I mix it with (water), I'm going to get a reaction that creates a gas. And the gas is a flammable gas."

The gas is acetylene, he said.

Yoast said he then puts the lid back on the pumpkin, sticks the lighter through the hole in the back and — boom — the Jack 'O' Lantern's eyes, nose and mouth are blasted out of the gourd on bright yellow flames.

"This is a lot of fun," Yoast said of his annual experiments.

Eighth-grader Aubrey Campbell said the explosions were "scary," but she preferred the hands-on experiment to textbook lessons.

Eighth-grader Trey Norton lauded his teacher.

"I like Mr. Yoast," Norton said. "We always learn a lot in his class."

Yoast said the discussion on energy that preceded the explosions was a way to weave Colorado Student Assessment Program subjects into the classroom.

"When you guys take CSAP in late March, early April, energy is one of the biggest topics," Yoast said to the class.

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