Today Natalia went to a birthday party, and came home with a blue, star-shaped balloon, cowboy hat, and green balloon sword. Later I did a small test.
On the way home, in the car, I tried to pinch it, and could not. But when we got outside, I could pinch it so that the material touched. But when we got inside it blew up again.
That proves that in different temperatures, air moves into particles.