chew

Chewing gum is a type of gum made for chewing, and dates back at least 5,000 years. Modern chewing gum was originally made of chicle [糖胶树胶], a natural latex. By the 1960s, chicle was replaced by butadiene [丁烷] -based synthetic rubber which is cheaper to manufacture. Most chewing gums are considered polymers [聚合物]. A polymer is a chemical compound with large molecules made of many smaller molecules of the same kind.

One of the best known chewing gum manufacturers worldwide is Wrigley. Wrigley was founded by William Wrigley, Jr. in 1892 in Chicago. It was known as Wrigley's Spearmint Gum in 1906 and within four years was the bestselling gum in the U.S. and is still the largest market producer of gum in the world. According to Wrigley surveys, the average American chews 300 sticks per year. Historically, during and after World War II, the image of an American soldier chewing a piece of Wrigley's gum became an icon in the American media. Wrigley began donating their gum to the troops, and it was regarded as a stress reliever and a healthier alternative to smoking.

Many schools do not allow chewing gum because students often dispose of it inappropriately, the chewing may be distracting in class, and the gum might carry diseases or bacteria from other students.

The Singapore government outlawed chewing gum in 1992 because it was becoming a danger when it was wedged in the sliding doors of underground trains. However, in 2002 the government allowed sugarless gum to be sold in pharmacies if a doctor or dentist prescribed it. Sugar-free gum sweetened with xylitol /'zailətɔl/ [木糖醇] has been shown to reduce cavities [牙齿中的洞] and plaque [牙斑]. 益牙是中国雅客食品旗下的口香糖品牌，创立于1993年并推出木糖醇口香糖。

Disney, Universal Studios, Seaworld, Amsterdam Schiphol Airport, and Busch Gardens Theme Parks have banned the selling of gum to help keep the grounds cleaner.

Chewing gum is commonly stuck underneath benches and tables or to the surface of sidewalks, and is difficult to remove once dried. Gum bonds strongly to asphalt [沥青] and rubber shoe soles because they are all made from polymeric hydrocarbons [烃; 碳氢化合物]. In 2000, a study on Oxford Street, one of London’s busiest shopping streets, showed that a quarter of a million blobs of chewing gum were stuck to its pavement.

六级/考研单词: chew, gum, synthesis, rubber, manufacture, compound, molecule, accord, icon, medium, donate, heal, alternate, seldom, disposition, distract, bacteria, outlaw, wedge, subway, pharmacy, dental, prescribe, cavity, studio, underneath, million, pave

 雷克雅未克人行道上的口香糖残迹