Question 1
This is a fascinating topic. Tectonic plates can be thought of something that is an enlarged form of a kitchen plate. When two of these huge plates meet, one forces another to go lower into the earth's mantle (a below surface geologic location made of rocks and molten (soupy or liquid) rocks.
This process of one plate forcing another to go lower is called subduction. The rocks grind away on each other. They are subjected to 6 different forces, the most common of which are friction, compression and folding. Add heat and you get metamorphic rock. It's like a kitchen recipe but on a much bigger scale. That's the cook's tour of Metamorphic rock.
Question 2
Mechanical weathering is a process similar to what is written above. If the sea pounds against the shore, eventually the rock will break down. Where I live, if water gets into a rock's cracks, when it freezes and the ice expands it will eventually break the rock apart. In short, big rocks become little pebbles.
Chemical weathering: water and minerals combine to react with the minerals contained in rocks. I'm not well versed in this area, so I'm not sure I could give you a good example other than this one. One of the biproducts of refining oil is sulfur dioxide, especially with Alberta oil which is very "heavy" and tar like. This combines with water to produce H2SO3 which is not an extremely strong acid, but it is still an acid. It can react with the minerals in a rock and you have the break down of a rock.
