Asubstance that contains only one kind of matter is known as a (n)

In the 1980's, congress authorized the u.s. department of energy to build the wipp facility in the chicuahuan desert in new mexico. what is the purpose of wipp?

Asher cycles 12 miles in 16 hours. what is his speed?

Asheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200oc and is permitted to achieve a steady-state diffusion condition. the diffusion coefficient for nitrogen in steel at this temperature is 6 x 10- 11 m2 /s, and the diffusion flux is found to be 1.2 x 10-7 kg/m2 -s. also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3 . how far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3 ? assume a linear concentration profile.