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Chemistry Facts

Why Does Cement Set?

Concrete has been known for literally thousands of years. It is a testament to the enduring strength of this material that concrete structures from those long-ago times are still standing strong ... Continue reading

Image of microstucture predicted from a NIST-developed model of cement hydration.

How Sublime

Show of hands. How many of you can't resist playing with dry ice? Dry ice is carbon dioxide frozen to -109.3 degrees F (-78.5 C). Throw a piece in water and it bubbles and boils. Expose a piece to air ... Continue reading

Sublimation of Comet's Tail

Nitrogen Gas and Compounds

Nitrogen is a very interesting element. It is the seventh element of the periodic table, with seven electrons in its atoms. The somewhat unique combination of electronic structure and small atomic ... Continue reading

Certain crops help the nitrogen cycle.

Knocking the NOx Out of Coal

Nitrogen is the most common part of the air we breathe. In fact, about 80% of the air is nitrogen. Normally, nitrogen atoms float around joined to each other like chemical couples. But when air is ... Continue reading

Air is mostly nitrogen molecules (green in the above diagram) and oxygen molecules (purple). When heated hot enough (around 3000 degrees F), the molecules break apart and oxygen atoms link with the nitrogen atoms to form NOx, an air pollutant.