Why is Aluminium more common in the earth s crust than iron?
Because aluminium is more reactive with other elements such as silicon and oxygen than ironThere is too little silicon and oxygen in the Earth to bind all available metals, so preferentially bonds to the more reactive metals leaving free iron metalBecause Iron metal is far denser than silicate rock, all of the free iron metal differentiated in to the Earth's core, leaving the silicate Earth (which includes the crust) heavily depleted in ironThe crust is also ultimately derived by partial melting of the mantleThe Al-rich minerals tend to melt out of the mantle in preference to the Fe-Mg ones (principally olivine), so the magmas that ultimately formed the crust, are further enriched in Al.
Paper and paper products (cardstock, cardboard, etc.) won't burn until they reach 451 degrees Fahrenheit (in fact, Fahrenheit 451 is the name of a famous novel about book burning) Usually, colored papers are fine to that temp too It's unlikely, but possible, that you could have problems with paper-products that have been painted (like cereal box cardboard) in that the paint could darken, but most likely the painting would only cause the cardboard to warp in too much heat (in effect, the side the paint is on would shrink) So paper is fine for shrink plastic, but more often something stiffer is used so that everything can be put in and taken out of the oven easilysomething like matt board, or even an index card, or a smooth unfinished wood board, or even a terracotta tile (or the back of a ceramic tile)You don't want anything that has an uneven surface though since it's possible the shrink plastic could end up not completely lying flat in the final momentIt's often suggested to put a bit of cornstarch on the heating surface too just to keep any part of the shrink plastic from sticking to the heating surfaceYou could also use parchment paper, I guess, since it's often coated with silicone (and nothing sticks to silicone), but again that kind of paper can be floppy or not lie completely flat HTH, Diane B.
