Yosefa Schoor Silber had no intention of establishing an international not-for-profit organization when she started visiting hospitalized New York children during her sophomore year at Yeshiva University’s Stern College for Women.

But when she recognized a need, she decided to fill it.

Now, just over four years later, TEACH (Together Educating All Children in Hospitals) boasts about 750 volunteer undergraduate and graduate students in the United States and Israel, mostly biology or chemistry majors and medical students.

They bring hands-on bedside science activities to children in 14 hospitals and medical centers, including two in Israel. In the last year alone, more than 75 “modules,” as TEACH refers to the science experiments, have brought smiles to about 550 children.

“I didn’t feel the children were stimulated enough, and I saw we could provide so much more for them from our true love of science,” Ms. Silber said. She grew up in West Hempstead in Rockland County and now is a third-year medical student at Albert Einstein College of Medicine in the Bronx.

As it turns out, at around the same time Yeshiva University senior Yair Saperstein of Cedarhurst, N.Y., had a similar notion. Once the two students connected, they honed their plan and presented it to the dean of Einstein, Dr. Edward Burns. He was more than enthusiastic.

“He said, ‘Let’s make it happen,’ and he handed us a check to pay for the first modules,” Ms. Silber recalled.

The lava lamps module uses water, oil, food coloring, and Alka Seltzer to build bottle lava lamps, similar to the ones popular in the 1970s.

They began TEACH at the Children’s Hospital at Montefiore in the Bronx. They started with two modules, which they called Chemistry Lava Lamps and Physics of Roller Coasters.

“Each time, a handful of students from Yeshiva would enter the hospital with two bags of supplies in hand, and tons of good intention and desire to help,” Ms. Silber said. “Our only goal was to engage as many patients and patient siblings as we could find. The founders had no idea of the exponential growth TEACH would see.”

In a little more than a year, TEACH had expanded to nine hospitals in the New York/New Jersey area. Current volunteers include residents of Englewood, Teaneck, Fair Lawn, Bergenfield, and Glen Rock.

The biggest core group remains Yeshiva University students, but the program now encompasses 22 hospitals in five states. Not all the student volunteers are Jewish.

“To many of the volunteers, TEACH is seen as a Jewish program, a ‘tikkum olam’ of sorts, a way of giving to the community,” said Dr. Saperstein, an Einstein graduate.

“Indeed, the founders, directors, the initial benefactor, and many of the volunteers past and present are Jewish,” he continued. “However, to my knowledge, our patients and their parents view TEACH through a social-justice lens, not necessarily as a Jewish program. This duality works well. We are not exclusionary toward Jews, yet the program fulfills our Jewish value of giving to the community.”

Dr. Saperstein said that students sign up to volunteer with TEACH for a variety of reasons. “Some want the experience of working in a hospital, others love the joy of teaching and want the opportunity to do more, yet others want to be a part of a program that will look good on their CV,” he said. “Regardless of their initial motivation, our volunteers come to intrinsically love TEACH and to want to participate more, and this fuels its popularity.”

In the bridge building module, children make different structures out of toothpicks and Styrofoam balls or gumdrops and test the structures with weights. They’re looking to learn which structures can support the most weight.

Amy Bravman, a Barnard senior from Fair Lawn, volunteered to serve as the Columbia liaison with Harlem Hospital. She recruited a new batch of underclassmen this semester for monthly visits to begin in the spring semester.

“People seem really excited about it. Within 12 hours of publicizing our recruitment drive, we had 30 people interested,” Ms. Bravman said. The Frisch School graduate is creating a schedule with Harlem Hospital’s child-life specialists and training the volunteers how to do the science experiments.

A “hospital leader” on each participating campus is in charge of creating the curriculum of simple science experiments and ordering, storing, and distributing the materials for the modules, which generally are geared to children between 8 and 15 years old. TEACH always coordinates with each hospital’s child-life specialist.

Isaac Snyder, now TEACH’s executive director and president, started out as a volunteer while he was a student in Yeshiva University. “My first module was at Downstate Medical Center, and I had one patient who’d tried to run away from the hospital,” Mr. Snyder said. “He not only loved the module I brought but didn’t let the staff take the experiment from his bedside.

“That experience made me want to go into healthcare and try to help the organization expand. I graduated from YU last May and now I’ve applied to medical school.”

When volunteers bring TEACH modules to the pediatric ward, they begin by introducing themselves, explaining what school they’re from, and detailing what the science project will entail.

“They ask some interactive questions, like ‘Do you think yeast and sugar will blow up a balloon?’ Most kids say no, although if you ever made challah you know it will,” Mr. Snyder said.

Each interaction lasts between 45 minutes and two hours, depending on the hospital, the children’s condition, and their ages. “We have to tailor the program to each hospital and its rules,” Mr. Snyder explained. “In some hospitals we work one-on-one, in some hospitals we work in groups in a playroom or even in an ER, and in other hospitals we work both in a playroom as well as at bedside.”

“One of the challenges of TEACH is that the age range in any pediatric ward is from toddlers to teens,” Ms. Silber added.

TEACH’s leaders often receive letters of gratitude.

“I’d like to compliment the incredible program which you have and for sending your volunteer,” a parent wrote. “She was pure joy from the moment she walked in. So patient, kind, and loving. The time spent with her, my child felt like a kid with a friend for the first time in a while. We are thankfully out of the hospital but still speak of her and her exciting science projects.”

Vivian Alestra, a child-life specialist at Staten Island University Hospital, wrote: “Your first visit to our Pediatric Unit on November 3, 2017 was an incredible success. I was so very happy to meet you all and even more impressed at how prepared your TEACH group was for this hospital visit. We had been expecting a Lava Lamp activity/experiment but also got an awesome Salt Painting activity/experiment as well. The children were so very excited, happy and engaged at every turn. … I am glad that I decided to go with your group and hope to have a continued visiting schedule with TEACH to our hospital’s Pediatric Unit.”

In its early years, TEACH was funded by Einstein’s Community Based Service Learning department. In its second year of operation, it received a grant from Neal’s Fund, Yeshiva University’s social entrepreneurship fund providing micro-grants for student charity-based startups.

TEACH now receives an annual grant from the Englewood-based Atran Foundation. Some of the medical schools support its branches, and the rest of the organization’s budget comes from participating hospitals, donations, and other grants.