Nitrogen is a gas that is all around us. It makes up about 78% of the Earth's atmosphere! In the gaseous state, nitrogen is a harmless, or inert, gas. It does not react with most substances. This is because the electrons in between two nitrogen atoms create a very strong bond between the two atoms. The bond is very hard to break, so the two nitrogen atoms cannot react with most chemicals.

Because it is inert, nitrogen gas is very useful in many products. For instance, it is used to preserve food such as the beef you see in the supermarket. The beef is a bright red color when you buy it. This is because the package that the beef is in has been filled with nitrogen to preserve the meat. The nitrogen prevents oxygen from getting in the package and turning it brown. If you see an old package of beef, it is usually brown because the nitrogen has leaked out, and oxygen from the air has gotten into the package and reacted with the beef. Scientists also use nitrogen gas in the same way to protect their samples from oxygen or other reactive chemicals. They can store their samples in nitrogen gas, and it will help the samples last longer than if they were stored in air.

Everything around us is made of tiny pieces called molecules. Just like when you play with Lego bricks and build something big from many small pieces, these molecules come together to form plants, animals, buildings, rocks, even you and me! Molecules are too small for us to see with our eyes, but scientists have proven that they exist.

Nitrogen is one kind of molecule. When you breath air, most of what you breath is nitrogen gas. With every breath, you take in more nitrogen molecules than there are grains of sand on earth! At very low temperatures, nitrogen can also be a liquid instead of a gas. Scientists use liquid nitrogen every day to keep things cool, like a super cold refrigerator!