SCITUATE — If 100 families attend a contra dance party in North Scituate tomorrow evening, it will shield the earth’s atmosphere from 140 pounds of carbon dioxide that otherwise would spew into the air.

That’s the calculation of two students at Scituate High School, who are studying how to conserve energy. To reach that figure, freshmen Joe Sanita and Daniel Tamayo, students of physical science teacher Shannon Donovan and members of an energy team, toted up the energy required to operate a 180-watt television and three 70-watt light bulbs. These energy-gobblers would be turned off if a family left their home and headed to the dance. Then the students multiplied the energy saving by 100, the number of families they hope will come.

Sanita and Tamayo said the group gathering also would prevent “significant amounts of sulfur dioxide, nitrogen oxides, volatile organic compounds, and particulates” from entering the ecosystem.

To save even more energy, the pair suggested that families form carpools for the dance, and drive hybrid cars or ones using biodiesel.

Said Sanita: “This might not sound big, but if this causes people to change their habits, then the impact could be huge.”

Donovan said yesterday that her freshman students are all assigned to do a project involving community energy.

“They have to pick any habit or technology that can help people reduce energy waste or retain more renewable energy,” she said.

The students assemble their projects between December and February.

Donovan said the dance is a first for the energy projects, so she does not know how many families will attend the affair, from 7 to 10 p.m. at the headquarters of the Scituate Preservation Society in the Historic Grange Building 33, 706 Hartford Pike.

Sanita said, “If kids spend time with people instead of computers or televisions, they can save energy and form better relationships.”

Tamayo said, “Other things, like reading, exercising, or playing games that don’t use electricity, can help make us smarter, stronger, and better connected to the people around us. So, we have organized a dance so that people in our community can spend time together. It’s a contra dance, not the usual kind of high school dance. This is fun for all ages.”

Local musicians Elwood Donnelly, Aubrey Atwater and Kevin Fallon will provide the music.

As for energy expended at the dance, the students have that covered, too.

The school energy project will offset the emissions associated with the dance by purchasing wind credits through People’s Power and Light (PP&L).

PP&L, Rhode Island’s nonprofit energy consumers’ alliance, focuses on advancing energy efficiency and renewable energy through cooperative purchasing, education, and advocacy. PP&L operates the GreenStart program, which allows consumers to offset their home electricity use. PP&L is supporting the high school project’s education efforts by making a small donation to the project each time a household signs up for GreenStart and indicates Scituate High School as their partner organization. Families can sign up for GreenStart at RIPower.org.

PP&L also runs an oil bank that collects donations to help people who are forced to choose between heat and food because of financial hardship. Last year the bank distributed more than $25,000 worth of fuel to provide warmth to those who need it the most.

The music for the dance is being sponsored by Scituate Advocates For Everyone (SAFE), so donations made for entrance to the dance will go to the oil bank.

tmorgan@projo.com