Explanation:
Once the earth's atmosphere was formed it really hasn't changed since, this is due to many reasons. Whatever created the earth's atmosphere (we don't know) has long disappeared, because of this the atmosphere cannot change, as there is nothing on earth that can change it (that we know of at least). Hopefully this helps.
I believe it is "The temperature of the ice sheet will be lowered" because it will most likely lower just a bit due to the heat. It's not going to fully melt but it will lower just a bit.
Plus I like your profile pic.
This is a chemical property due to radioactivity being a chemical characteristic of uranium. This fact describes its chemical structure.
The surface area is greater with the crushed solid so more of the material is exposed to the gas allowing more reactions
