Volume changes of solids

Volume Changes of Solids in Different Atmospheres. The fact that small MgO crystals prepared in vacuo and in air have different lattice parameters means that a crystal prepared in vacuo expands when brought into air. 

At liftoff, a space shuttle uses a solid mixture of ammonium perchlorate and aluminum powder to obtain great thrust from the volume change of solid to gas. In the presence of a catalyst, the mixture forms solid aluminum oxide and aluminum trichloride and gaseous water and nitrogen monoxide. 

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