CHEMISTRY

5. the parts of a building that are made of stone.
8. to make something sharp or smooth by rubbing it on a rough hard surface.
11. a hard block of baked clay that is used for building houses, etc.
12. a salt in which the anion contains both silicon and oxygen, especially one of the anion SiO42−
13. real or definite; not only existing in the imagination

1. a rock that is formed chiefly by accumulation of organic remains (such as shells or coral), consists mainly of calcium carbonate, is extensively used in building, and yields lime when burned.
2. a chemical process employed in polymer chemistry and process engineering that produces the toughening or hardening of a polymer material by cross-linking of polymer chains.
3. a soft black substance (a form of carbon) that is used in pencils.
4. reduces friction
6. a material or structure formed from a mass of fragments or particles loosely compacted together.
7. rock or earth from which metal can be taken.
9. a soft white rock like chalk that is used in the building industry.
10. a grey powder, that becomes hard after it is mixed with water and left to dry. It is used in building for sticking bricks or stones together or for making very hard surfaces.