When water changes from a liquid to a gas, it is?? A. Freezing B. melting C. evaporating D. condensing

But we pulled at the grill [on the ground] and it gave way. and then we saw iron rings as steps leading down a shaft into a darkness without bottom. … it was a great tunnel. its walls were hard and smooth to the touch; it felt like stone, but it was not stone. on the ground there were long thin tracks of iron, but it was not iron; it felt smooth and cold as glass. we knelt, and we crawled forward, our hand groping along the iron line to see where it would lead. but there was an unbroken night ahead. what is the most likely explanation for the walls described in the bold text?

Air is made of gaseous elements and compounds that interact but are not bound to each other. so air can be considered a

Em um acidente, um caminhão carregado de solução aquosa de ácido fosfórico (h3po4) tombou, derramando cerca de 24,5 toneladas dessa solução no asfalto. quantas toneladas de óxido de cálcio (cao) seriam necessárias para reagir totalmente com essa quantidade de ácido? 2 h3po4 + 3 cao → ca3(po4)2 + 3 h2o a. 14t b. 29t c. 42t d. 7t e. 21t