Condensation: from gas into liquid

When you breathe air out of your lungs, a large amount of water will also travel with your breath. You cannot see this water, because it is in its invisible, gaseous form. When the weather is cold, the water vapor in our breath condenses into small, liquid droplets, forming a cloud of fog. You can see this cloud of fog only for a short while. Similarly, if you breathe on a cold window glass, the water vapor in your breath will temporarily condense on the glass, making it appear foggy. 

Water also condenses high up in the sky, because the temperatures in high altitudes are cold. Small fog or cloud droplets can be seen forming clouds in the sky. The water droplets condense on the surfaces of small dust particles in the atmosphere. If you follow the movement of clouds for a long time, you can see some of them grow. This happens when humid air arrives near them from below. Other clouds will grow smaller, as their water droplets evaporate into water vapor. 


Image on the left: When you breathe on a cold window, the water vapor in your breath will condense on the glass, making it foggy. Image on the right: Water vapor condenses into liquid droplets when the temperature is cool. These small droplets of water form the clouds you see in the sky.

Air is a gas. If you wanted to condense air into a liquid, you would have to remove a large amount of heat from it. The condensation point of air would be somewhere near -200 degrees Celsius. Air is a mixture of gases that is mainly made out of nitrogen and oxygen. Liquid oxygen is used in space shuttles, whereas liquid nitrogen is used to freeze things quickly. In the image below, you can see a cook creating instant ice cream with the help of liquid nitrogen. 

If you could see things at an atomic level, you could perceive gas molecules moving everywhere in the air around you. In a closed container, the molecules of a gas will bump into one another and the edges of the container. This movement increases when the heat is increased. Conversely, when the amount of heat is decreased, the movement of the molecules becomes slower. Eventually, the molecules will cling on to one another and begin moving at a slower speed. When this happens, the gas condenses into a liquid. 


Image on the left: A chef preparing instant ice cream with the help of liquid nitrogen. Image on the right: When the temperature of a gas is decreased, the movement of its molecules becomes slower.