Air is a mixture of gases that primarily consists of nitrogen (about 78%) and oxygen (about 21%), along with trace amounts of other gases like carbon dioxide and argon. It is essential for life on Earth, as oxygen is necessary for respiration in most living organisms. Air has weight and exerts pressure, which is why we experience atmospheric pressure. The properties of air include its ability to expand and contract with temperature changes, making it less dense when heated. Air can also hold moisture, leading to humidity, which affects weather patterns. Additionally, air can carry sound waves, allowing us to hear sounds from a distance.