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60. How does the crystal structure of graphite allow it to be used like a pencil "lead" and as a common lubricant for locks? 62. Break-resistant glass is produced by the replacement of sodium ions on the glass surface with regular potassium ions, which are larger than the sodium ions. How this would make the glass more resistant to breakage? 65. Sodium chloride, table salt, is not deliquescent, but the magnesium chloride. Magnesium chloride is an impurity in common table salt. What effect might it not be desirable on a shaker full of table salt? what could be done to eliminate the problem? 66. Why is it not fair to speak of silicon carbide as a molecular substance, while its bonds are covalent?

60. How does the crystal structure of graphite allow it to be used like a pencil "lead" and as a common lubricant for locks? Crystal Graphite has a layered structure as shown in the following figure: http://upload.wikimedia.org/wikipedia/commons/5/5f/Graphite-layers-side-3D-balls.png because the layers are flat, and no bonding between the layers, there is little resistance to movement between the layers. Thus, it may be used as a pencil "lead" and as a lubricant for locks of Commons 62. Break-resistant glass is produced by the replacement of sodium ions on the surface of regular glass with potassium ions, which are larger than the sodium ions. How this would make the glass more resistant to breakage? Do not know. 65. Sodium chloride, table salt, is not deliquescent but the magnesium chloride. Magnesium chloride is an impurity in common table salt. What side effects might have on a shaker full table salt? what could be done to eliminate the problem? When a sample of table salt containing magnesium chloride as an impurity absorbed sufficient sufficient moisture, salt grains of May, sticking together to form a significant block or stick to the bottle, thus unable to shake. A simple way could be done to eliminate the problem is to have a watertight cap to the shaker, significantly reduce the intake of moisture. 66. Why is it not fair to speak of silicon carbide as a molecular substance, while its bonds are covalent? Because silicon carbide is a network of giant covalent bonds. You may not be able to call a block of silicon carbide 1kg as a "molecule", as a tire car or a piece of diamond.