英語時差:液態(tài)氣的燃點

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Flash Points People who work with chemicals make sure they know the flash point of each substance in their labs. A flash point is the temperature at which the fumes from a liquid can be ignited with a spark. But people who have never taken a chemistry course need to be concerned with flash points as well. For example, the gasoline you put into your car has a flash point of minus forty-five degrees Fahrenheit. So, unless you live in a climate where the temperature stays below minus forty-five degrees, the fumes from gasoline can ignite from a nearby spark. And that’s why most gas stations have warning signs posted about not smoking while you fill up your tank. Olive oil has a flash point of 437 degrees Fahrenheit. That means if you could heat olive oil to 437 degrees, it would give off a vapor that could ignite if a lit match passed through it. Cod liver oil has a flash point of 412 degrees Fahrenheit and formaldehyde has a flash point of 122 degrees. Most flash points are inconsequential to the lay person because they occur at such high temperatures. But some, like kerosene, with a flash point of 100 degrees Fahrenheit, can be cause for concern on a hot day. If you keep an old-fashioned kerosene lamp on your fireplace mantel, you probably shouldn’t light it on a hot summer day, or you might ignite more than just the wick of the lamp.