positive: 1 picometer [pm] = 1E-10 centimeter [cm]<br>Feet/Inches and Meters Converter<br>ftin<br>m<br>Sound<br>More about Length and Distance<br>Celebrity Reflectioncruise ship in the Port of Miami. It's length is 1047 ft or 319 m<br>The Golden Gate Bridge spanning the Golden Gate, the strait that provides an opening between the San Francisco Bay and the Pacific Ocean. Its total length is about 1.7 mi or 2.7 km.<br>Overview<br>Length describes the longest dimension of an object. For three-dimensional objects, it is usually measured horizontally.<br>Distance, on the other hand, refers to the measure of how far the objects are from each other.<br>Measuring Length and Distance<br>Units<br>The basic unit for length and distance in the International System of Units (SI) is a meter. Derivatives of the meter, such as kilometers and centimeters, are also used in the metric system. Units such as inch, foot, and mile are used where the metric system is not accepted, such as in the USA and the UK.<br>Dist
negative: “PPM”表示的是“百万分之一”,还有常用的比如“PPb”表示“十亿分之一”.这两数量单位一般是指痕量甚至更低的含量,如食品中甜蜜素的含量或者残留量等.\x0d对于你说的PPM所对应的mg/m3,1P<br>理想气体方程:P标*V标/T标=P实*V实/T实“标”代表标准状况,“实”代表实际工况.Nm3通常指温度为0℃(273.15开)和压强为101.325千帕(1标准大气压,760毫米汞柱)的情况.得根据<br>你所说的是重度单位间的换算问题,mg为质量,处处不变.m3为单位体积(条件没有确定),Nm3为标准状态下的单位体积,即在标准状态下(标准压力、标准温度)的单位体积.因此,如果单位体积不变,那是一样的.<br>其实有一个总的规律:ppm可以用在质量上,一公斤(kg)的物质中有一毫克(mg)某物质,某物质含量即为1ppm;也可用在容量上,一千升(kL)的溶液中有一毫升(mL)的某物质,某物质含量即为1ppm;<br>现在ppm这个单位已经被废除了,他的含义是10的-6次方,比如mg/kg,就是常见的ppm.如果是水溶液的话,1L水溶液质量为1kg,1ppm=1mg/kg=1mg/L.如果是气体的话ppm=10的-<br>1ppm可以看做1mg/kg也可以看做1mg/L.而1000L=1m3这样可以算出1ppm=1000mg/m3<br>这两个不是一个单位,PPM为浓度单位,是体积浓度,为100万分之一,而MG/M3是1M3内的物质毫克数,一般是用做有害场所的浓度值,也就是1M3的空间内有害物质的质量,两者可以换算,但是需要密度等参数<br>空气的密度在那?客空气的相对分子质量是29,可以算出密度不好好学习,就知道乱问,问题都不全看你考试怎么办吧?<br>ppm是英文partspermillion的缩写,译意是每百万分中的一部分,即表示百万分之(几),或称百万分率.如1ppm即一百万千克的溶液中含有1千克溶质.ppm与百分率(%)所表示的内容一样,只是<br>1g=1000mg,其他不变,所以1g/m3=1000mg<br>1ppm=1mg/Lppm可以用在质量上,一公斤(kg)的物质中有一毫克(mg)某物质,某物质含量即为1ppm;也可用在容量上,一千升(kl)的溶液中有一毫升(ml)的某物质,某物质含量即为1ppm;<br>简单的说:1ppm=1mg/kg=1