Air is essential to our lives, we breathe it all the time to stay alive. But, can we see it? Can we smell it? Can we feel it or touch it? Well, no. But, even if the air can't be seen, has no taste or smell, or we can not feel it or touch it, we know that it is everywhere around us by feeling its presence. We can feel its presence when we are sitting in front of a fan; when we fly a kite on a windy day; when the leaves rustle or branches sway. Actually, the air is everywhere on earth. Air is also located in the surface layer of the earth, in the soil, and it is also located around the earth in an air layer called the atmosphere. The air in the atmosphere is keeping the Earth from getting too cold or too hot, it protects us from too much sunlight, or protect us from meteoroids. Interesting?
In this lesson, we are going to learn:
Because it can't be seen, felt, or smelled, it is a question if the air really exists. Well, let's find out how can we prove that air really exists. The simplest way is by blowing up a balloon. If you take an empty balloon, it is shapeless. When you blow up the balloon, the balloon will expand, and take a shape (usually round), and we can feel the air pushing on the balloon. The balloon will get larger any time we blow air into it, which means that air actually takes up space. The balloon is expanding due to gases, water vapor, and other matter that air is made up of. They give air mass, so we can conclude that the air has a mass.
If the air takes up space and has a mass we can make a conclusion that the air is made up of matter, because we already know that matter is any substance that has mass and takes up space. So yes, the air really exists!
Under normal conditions, matter exists as either a solid, a liquid, or a gas. Air is a gas. It is an invisible mixture of many gases and dust particles, in which living things live and breathe. Air contains important substances, such as oxygen and nitrogen, that most species need to survive. It has an indefinite shape and volume. It has mass and weight. Now, let's closely look at the air composition.
The air in our atmosphere is composed of molecules of different gases. The most common gases are nitrogen (78%), oxygen (about 21%), other gasses, like argon (less than 1%), and other trace gases in the air, like carbon dioxide, helium, and neon. Air also contains water vapor. The amount of water vapor varies depending upon the location, (for instance, is it a tropical place or a desert). Also, air contains dust, pollen, and bacteria.
Apart from the two properties of air, that the air takes up space and has a mass, which we already discussed in this lesson, there are other properties of air too.
Air is made up of molecules that are constantly in motion. As air warms up, the molecules start to vibrate, increasing the space around each molecule. That will make the air expand and will become less dense, or lighter. Or, we can say, the same number of air molecules occupy a larger space or the same sized space with increased air pressure. When air cool, The opposite effect happens. As the temperature drops, molecules move more slowly, taking up less room.
The particles of air push in all directions and the force that is exerted are called air pressure. While air pressure can refer to the pressure of air within a confined area (balloon or basketball), atmospheric pressure specifically refers to the air pressure exerted by the air molecules above a given point in the Earth’s atmosphere. Even if the air seems light, there is a lot of it pushing down on Earth’s surface. We can experience high air pressure at sea level because the whole atmosphere is pushing down on us. The air pressure is low on top of a mountain because there is less atmosphere pushing down on us.
Differences in pressure and temperature, cause the movement of air, which is experienced as the wind.
When we take atmospheric air and then physically force it into a smaller volume, as a result, bringing the molecules closer to each other, the molecules take up less space and the air is compressed. Compressed air is made of the same air we breathe, but that air is compressed into a smaller size and kept under pressure. Compressing the air makes the molecules move more rapidly, which increases the temperature. This phenomenon is called “heat of compression”.
Altitude means height above the ground or above sea level. As altitude increases, the amount of gas molecules in the air decreases and the air becomes less dense compared to the air nearer to sea level. The air would become "thin". Thin air exerts less pressure than air at a lower altitude.
Air consists of one of the main life-sustaining gas called oxygen. Living things breathe in and breathe out this air. In humans, the air is pulled into the body by the lungs and used to fill tiny air sacs that allow blood cells to pick up oxygen, which is then distributed across the body's cells. The oxygen can then be used to break down sugars and create energy through the process of cellular respiration.
Nitrogen and Carbon dioxide are also other gases that are vital for plants and their growth. Plants need carbon dioxide for the process of making food, called photosynthesis. They take the carbon dioxide from the air, and as a result of photosynthesis, release oxygen back into the air.
Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat. Oxygen in the air supports the chemical processes that occur during a fire. When fuel burns, it reacts with oxygen from the surrounding air, releasing heat and generating combustion products (gases, smoke, etc.).
Air helps in maintaining the temperature on the earth's surface by circulating hot and cold air. Air acts as a conductor of heat as well.
