Which energy resource disturbs the land the most, producing a lot of pollution and requiring large smokestacks to remove much of it?

coal

fuel cells

hydroelectric

natural gas

Copper, silver, aluminum, cobalt, chromium, mercury 

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.