How about learning chemical symbols while helping to end world hunger? Need to brush up on your favorite classic painters? Improve your vocabulary? You can do all these things on Free Rice, a site run by the United Nations World Food Bank.

You select a topic area and the degree of difficulty you want to tackle for a series of multiple choice questions that appear on the screen. With each correct answer, you donate 10 grains of rice to the Food Bank, courtesy of the Food Bank’s sponsors. (Incorrect answers, however, do not subtract grains from your pile!) In 2008, nearly 44 billion grains of rice were donated thanks to Free Rice players around the world.

Beware: You and your students might learn something while having fun playing this rather addictive game!