The silver reacted with the oxygen in the air, this chemical reaction caused it to tarnish.
Answer:
I believe it is hydrogen for the first and methane for the second.
Explanation:
Answer to 8: The most dangerous or harmful gas to humans in the atmosphere would be carbon dioxide. But reserchers have found that methane levels in ancient air samples and found that scientists have been vastly underestimating the amount of methane humans are emitting into the atmosphere via fossil fuels.
Answer to 7: The type of gases present are as critical to density as elevation and gravity, and all are interrelated. Certain atmospheric gases will create thick atmospheres. For example, atmospheres with abundant hydrogen tend to be thicker as gases will combine with hydrogen for greater mass.
Hope this helps!
Answer:
When mechanical waves strike a barrier, at least part of the energy of the waves will be reflected back into the media from which they came.
Explanation: