Hello! Allow me to help!
Your question: Prove that air is a mixture of gases
My answer: Air is a mixture and not a compound because: Air does not have a formula like a mixture, while compounds have a fixed formula. When air is formed by gases, there is no energy change. Components of air can be physically separated.
Why is this correct? Good question! Allow me to explain: Air is composed of various gases such as nitrogen, oxygen, carbon dioxide, inert gases and so on.Moreover , dust particles and water vapour are also present in the atmosphere because of which air is mixture.
Hope this helps! UwU
-Maxwell