Question

What gas is inside the bubbles we sometimes see in an ice cube?

Answer 1

Air..........?

Explanation:

Do you mean the bubbles that you often observe the in an ice cube?

And we presume that this is simply air. When a compound solidifies, it (often) expels the molecules that are dissolved in it. Air (as a gaseous mixture) is always dissolved in the water we drink. When water freezes it can expel the gases it has dissolved in solution.

I apologize if I have missed the point of your question.