Pacific Balloons

1. The Pacific Ocean is a heterogeneous compound because it has water, salt and other things dissolved. It also has a lot of sand and other solids are not dissolved (oh yeah, fish and all sorts of other things). If you take a sample of the ocean in a region, you will probably get different things in the sample compared to another sample in another area. One could imagine that the brown water in the middle of a crashing wave will be different than the blue / green water near a pier.

2. Air in a balloon is a homogeneous mixture. If you take a small sample of the mixture, it will be the same as any other sample. In other words, it will have the same proportions of different chemicals that compose it. The air is composed of different gases - oxygen, nitrogen, carbon dioxide, water vapor, etc. No matter how you sample, you'll get the same proportions of these materials

3. Aluminum is an element. Here's a hint - it has a symbol (Al). No matter how you divide it, you'll always have the same material - aluminum. There is nothing in it, but - it is a pure material.

Pacific Ocean = hetero

Aluminum element =

air in the balloon = homogeneous

read the guidelines I posted in another of your questions