"If contemporary art can teach us anything." Joan Mondale said yesterday, "it is that context changes content."

The art she has installed in her official residence is more than decoration. The wife of the Vice President is using her position to support modern art.

The first work one encounters when one enters the front door is a lithograph of the ale cans by Jasper Johns. The last thing one sees is the print by Robert Rauschenberg that made the cover of her book,"Politics in Art" three years before the artist made the cover of Time magazine. Fifty other works, must be borrowed for a year from Midwestern museums, have been installed between them. The furnishings are bland. The color scheme is white and biege. The decor is so anonymous - and the works of art so striking - the visitor feels commanded to think about modern U. S. art.

At a press luncheon yesterday, Mrs. Mondale spoke of her "commitment to all the arts." She paused. "Especially the visual arts," she said.

Her uncle, Philip R. Adams, was for three decades director of the Cincinnati Art Museum. Mrs. Mondale herself has wroked in art museums in Minneapoliss, Washington and Boston. "It's wonderful," says one museum official, "to have a friend in court."

Betty Ford did it for the dance. Lady Bird Johnson did it for trees and flowers. The art world expects Joan Mondale to do as much for art.

There is reason for that optimism. Already she has:

Chosen an art specialist for her staff. She is Mary Ann Tighe, 28, now an education specialist at the Hirshhorn Museum and Sculpture Garden. Tighe, whose art criticism has been published in the New Republic. The Washington Post and other periodicals, is the author of "Art America," a survey of American art which is scheduled to be published soon. At the University of Maryland, she did her master's thesis on Max Ernst.

Asked the concessionaires of the National Park Service to offer, in their gift shops, fewer plastic trinkets and more works handmade by craftsmen. Addressed museum trustees at the National Gallery of Art. It is important," she told them, "not only that you take pride in your achievement, but that you be recognized for it by your nation and your nation's government."

Attended the openings of the museum retrospectives of Alexander Calder (in New York) and Rauschenberg (in Washington).

Asked 40 museum directors to a reception at her house. They visited her Sunday to see the art displayed.

Mondale is expected to encourage federal departments to install works of art.

The Mondale collection ranges from the academic to the experimental. It includes a little bronze of 1933 by Paul Manship, the Minnesota native who did the shiny statues for New York's RockefellerCenter, and a piece - of knotted rope and wood - by

"Isn't it enigmatic?" asked Mondale. "Isn't that rope a mess?"

Among the other sculptures are a 6-foot bronze by Isamu Noguchi; "Star Cage" of 1980, a superb welded steel drawing by the late Davis Smith; two works by Louise Nevelson, a pivoted steel piece by Mark di Suvero, and "Alphabet in the Shape of a Good Humor Bar," 1975, by Claes Oldenburg.

The Oldenburg is displayed beside an Andy Warhol soup can. It's our pop art corner," Mondale explained.

Some of America's best known painters are also represented. They include Edward Hopper ("Sunday," his 1926 oil, on loan from Washington's Phillips Collection, also was reproduced in Mondale's book;) Georgia O'Keefe, Roy Licthenstein, Sam Francis, Robert Motherwell, Hans Hofmann, Willem de Kooning, Richard Estates, Jacob Lawrence and Elleswork Kelly.

Younger artists, among them Washington's Sam Gilliarn, also are represented. So are Thomas A. Rose and George Morrison. Minnesota artists Mondale calls "unknown."

She was aided in her choices by Martin Friedman, director of the Walker Art Center, Minneapolis, a longtime friend. It is clear from the way the colors of the Gottlieb echo those of the Ellsworth Kelly, and from the mix of small and large works, that their intention was not just to honor modern art but to grace a home. The art looks fine.

The works were borrowed from museums in Detroit, Kansas City, Ann Arbor, Madison,Des Moines, Lincoln and othe Midwestern cities. They will remain on view one year. "Next year," said Mondale, "I'll work with a Texasmuseum and replace these objects with Southwestern arts and crafts."