May 17, 2006 - Wearing khaki shorts and tennis shoes, the curly-haired science teacher watched a pair of goggled students conduct an experiment.
"What are we trying to do here?" junior Mick Burton wondered.
"We're figuring out how much of a base it takes to neutralize the acid, I think," sophomore Jenai Crump responded, eyeing some sodium hydroxide - the base - in a graduated cylinder.
The pair dripped some of the base liquid into a beaker of unknown acid. After a few drops and some stirring, the acid should change color. The pair's acid remained clear.
Mountain View High School science teacher John Madden offered a tip.
"Don't forget the indicator," he said, holding a thermos of coffee and smiling beneath his mustache.
"Yeah, the Pheno!" Burton remembered.
"You don't get a color change without an indicator," Madden said.
Crump added a drop of Phenolphthalein and the duo tried again. After a certain number of drops, the acid turned clear to pink.
"Okay, now we have to figure out what that means," Crump said.
Madden walked away.
The veteran teacher considers his fourth-hour chemistry class "the largest and the loudest." He also considers them his best students.
On the morning of May 11, some students worked on a review sheet, a few worked on labs and some played cards, seemingly uninterested in binary compounds, common polyatomic ions or neutralizing unknown acids. The latter group probably will fail the class.
"It's up to them," declared Madden, who began the day's class by cranking up the volume on "Classical Gas," the popular instrumental made famous in 1968 by guitarist Mason Williams.
Madden begins each class with loud music. He plays Hawaiian music, folk music and each Friday, the Beatles.
Despite criticism and occasional sluggish students, Madden sticks to his guns, employing a self-paced technique he learned years ago from a college professor.
"(The students) have a responsibility for their learning. We tell them what work they have to do. We give them suggested due dates, but when they do it is basically up to them."
Two weeks ago, Madden met President Bush, who gave the teacher a national award for his classroom method. Nationwide, 107 math and science teachers got the award.
Madden's chemistry students must complete 26 units of material. Last week, most students worked on the last, while others seemed content to finish only a dozen or none at all.
Early in the semester, Tim Cheves goofed off and fell behind. Then one week, the sophomore churned out six units.
"Were you shocked?" Cheves asked his teacher.
"I was, but you still have to show you know it," Madden shot back.
Students need to pass quizzes at 90 percent proficiency to pass the class. "They have to have near perfection on quizzes," Madden explained.
Students sometimes struggle with the independence. Burton would rather have a teacher show him how to do everything, he said last week during his lab.
Madden makes no lectures in his chemistry classes. As students filed into class last week, he joked about the "geriatric fish" in the classroom's tank - aging balla sharks that stay put most of the time.
When the bell rang, he clasped his hands together and said, "Alright, let's go."
Students got in groups and worked on handouts. Sophomore Michael Heara worked alone on a review worksheet. He looked over a lab exercise in which he created scents from mixing alcohols and hydrochloric acid.
When he mixed ethanol and acetic acids, the solution smelled like nail polish, he noted. Salicylic acids and methanol create a "winter fresh" aroma.
Madden doesn't leave his students out to dry, Heara said.
"He does a little prodding. He has (students) that try to make it and ones that don't," he added, motioning toward the group playing cards.
"But then we still ask (Madden) questions every couple minutes," said sophomore Sam Grantham, who along with Kassy Hunter, already has finished the semester's work.
Hunter wanted to spend her free time coloring, while Grantham thought about joining the card game.
"I've decided that being done early is not that fun," he said.
Teenagers must manage their time to pass his class, Madden said. The advanced students "fly," which leaves the teacher more time to guide those students who struggle to grasp the material, he added.
"A number of parents don't perceive what I do as teaching, because I'm not standing up there telling them everything they need to know."
He gives no busy work. If students do three out of 20 equations correctly, he won't make them do the rest.
"You just have to do enough to show you know it."
Fellow Mountain View teacher Chuck Wallum next year will use a pared-back version of Madden's self-paced style for his chemistry classes, too.
Wallum's class probably will contain more elements of familiar teaching styles, he said. The teacher hasn't bought all the way into the self-paced method.
"It doesn't have to be all or none," Wallum said. "I'd like to say this thing works for everybody no matter what, but I realize it doesn't."
For now, Madden restricts the self-paced philosophy to chemistry. He teaches his freshman science and advanced placement environmental science courses in a more traditional way, making use of lectures and class discussions.
Since his first class at Mountain View in 1988, Madden has remained the toughest and most rewarding kind of teacher, as a friend's drawing illustrates.
In a caricature of him that hangs on the classroom wall, devil horns rise from the Madden's head. He carries a pitchfork and spews the numbers 666.
The 46-year-old Mountain View High School teacher takes the joke in stride.
"There's a small angel halo on the head, too," he quickly points out.
A few years ago, he gave Marana Unified School District board member Bill Kuhn's son a 'D' in class. When Kuhn questioned Madden, the teacher laid it out.
The boy earned the low grade, Madden told Kuhn.
"He didn't do the required work in the required time," Kuhn recalled Madden saying.