An amorphous solid can sometimes be converted to a crystalline solid by a process called annealing. Annealing consists of heating the substance to a temperature just below the melting point of the crystalline form and then cooling it slowly. Explain why this process helps produce a crystalline solid.

Give the formula of a solid containing Si that is (a) molecular (b) ionic (c) network covalent

The test tubes shown here contain equal amounts of the specified motor oils. Identical metal spheres were dropped at the same time into each of the tubes, and a brief moment later, the spheres had fallen to the heights indicated in the illustration. Rank the motor oils in order of increasing viscosity, and explain your reasoning: