To demonstrate that air is matter, one can show that it meets the criteria of occupying space and having mass, as evidenced by an inflated balloon that increases in size and weight.
To convince your friend Dayana that air is matter, you can explain that matter is anything that has mass and takes up space.
Air might be invisible and easy to compress, but it still meets these criteria. For instance, when a balloon is inflated, it becomes larger because the air takes up space inside it.
Additionally, the balloon weighs more when it is full of air, proving that air has mass. The fact that we can measure this difference with a sensitive scale further confirms that air has mass.
Scientists have also managed to compress gases into liquids, clearly demonstrating that gases, including air, are indeed forms of matter, just like solids and liquids.