Wesley Horst listed the ingredients of a powder as he tried to explain the rudiments of chemistry to a group of second- and third-graders at Allegheny Valley Library in Harrison.

"Citric acid, malic acid, calcium phosphate, ascorbic acid ... "

One of the students, Isaac Beck, squirmed in his seat, leaped suddenly and shouted.

"That's going to explode!"

Mr. Horst chuckled, revealed that the powder was Kool-Aid, and continued on with his lesson.

The class was the first of a four-day program called Science in the Summer, sponsored by GlaxoSmithKline. It runs Mondays through Thursdays and will travel to 14 libraries in Allegheny and Beaver counties this summer. It's free and open to students in second through sixth grade, who can sign up at their local library.

Science in the Summer started June 23 with programs in Aliquippa and Ambridge.

Programs were also held in Brentwood, Dormont and Penn Hills, and before the end of summer, will be held in Crafton, Homestead, Green Tree, Moon and Scott.

Instructors from the Carnegie Science Center teach each program.

Malesia Dunn, director of communications at GlaxoSmithKline, said the program's atmosphere is more relaxed than a typical elementary school classroom.

"It's a much more fun environment [than school]," Ms. Dunn said. "It's very engaging; the hope is that the kids will be more interested in science when they return to school."

The resources provided by GlaxoSmithKline allow students to conduct experiments with materials that may not be available at most schools, Mr. Horst said. The activities for each week include an experiment with dry ice, creating borax crystals and making slime.

"Memorizing stuff is not all that helpful for most people," said Mr. Horst, who has worked as a staff educator at the Carnegie Science Center for three years. "We try to make sure that everything we do is interactive and hands on; things [students] can touch and sense, and things that connect with everyday life."

Science in the Summer also tries to fuel an interest in science among youngsters, with the hope that they will continue to study science in their future schooling.

"We have lots of cool things we want to do, but we don't have enough scientists to do them," Mr. Horst told kids at Allegheny Valley. "We're hoping that some of you will want to become scientists or chemists when you grow up."

Mike O'Connell, whose daughter Katie attended the Allegheny Valley program, thought it was a perfect summer activity for elementary students.

"It's the right age for them to start learning about science," he said.

Mr. Horst said the activities are specifically designed for younger children.

"There are many chemical reactions that are very simple, but they make kids go 'wow,'" he said. "We try to instill that sense of wonder to get these kids excited about science."

Susan Wilson, a librarian at Allegheny Valley who helped register students and set up the experiments, said the program is one of the most popular at the library.

"It offers the type of thing you don't find in a textbook, and you can build on that," she said.

"I consider it a privilege to host this. I did everything in my power to move our summer reading schedule around so we would be available."

GlaxoSmithKline started the Science in the Summer program in this area six years ago, and it has funded a larger program in Philadelphia for more than 20 years. Ms. Dunn said the pharmaceutical and health care company hopes to expand to more libraries in the next few years.

She also said the instructors from the Science Center, who provide staff for the program, do a "phenomenal" job.

Students are split into two groups; second- and third-graders go to the first session of the day, and older students attend the second. The 45-minute sessions are limited to 18 students, who receive free safety glasses, a textbook and an apron to use throughout the week and to take home after they finish. Students also are given a certificate on the last day of the program.

Allison Wygonik, a third-grader from Natrona Heights in Harrison, was especially excited when she found out she would be able to keep her safety glasses.

"These are so cool," she said. "My daddy has a pair just like them and now I have a pair of my own."