Air has mass, it takes up space, and it moves. A student will be aware that the wind blows on their face on a winter day but may not think of this as air moving. On a large scale, the movement of air is observed by changes in the weather. If you are mailing a parcel at the post office, the postmaster will try to squeeze all the extra air out of a parcel before determining the cost of mailing the parcel. Air can also keep a kite in the air or make a pinwheel spin. In addition to these physical properties, it is important to remember that all living things need air to breathe and to survive.