Identify each material as a compound or a mixture. caffeine contains hydrogen, carbon, nitrogen, and oxygen atoms in a fixed ratio.

caffeine is a compound.

Explanation:

1) As stated caffeine contains hydrogen, carbon, nitrogen, and oxygen atoms in a fixed ratio.

2) The definition of compound is a pure substance formed by chemical bonding of two or more fifferent elements. That means a defined ratio of the elements in the compound, which conferes uniform and equal properties to every part of the compound.

Some examples of compounds are salt (NaCl), water (H2O), vinegard (CH3 COOH).

A mixture combines several elements or compounds, not bonded by chemical bonds but mixed in ratios which may vary.

The answer is 4 i don't know if its right let me see.

C) the increase in atmospheric pressure pushes the walls of the balloon outward thus making it  is the answer.hope i you.