It might be hard to understand what a gas is because most gases are invisible!
A gas is the special state something is in when it's not a liquid and not a solid. When something is in the form of a gas, the little scientific units that make it up are more spread out than when it's in another form, and they're full of energy, too! Gases also do not generally have any color or any natural smell, either.
Think, for example, about the bubbles in a glass of soda. These little bubbles are a made from something called "carbon dioxide." Consider some of the qualities of these bubbles: The way that they are always climbing to the surface of the soda shows you that they have energy, and they'd be invisible if they weren't surrounded by the rest of the drink. (You don't see them after they reach the top and escape!) They are also odorless, and are not a liquid like the soda and are not a solid like the cup, either! So then are they a gas?? Yes!
At this point you might be thinking that gases are just air, which actually isn't too far off air itself is a type of gas! Most likely you area already familiar with more gases than you think: Air, carbon dioxide, and even the special helium that makes balloons float!
One really important gas that is all around you is something known as "water vapor." Water vapor is the name for water when it's in its gas-state and is not a liquid or a solid.
Water vapor causes lots of the changes that occur in the weather, such as snow, frost, and clouds!
Have a grown-up help you figure out one or two more gases that you might already be familiar with. Think about their characteristics and how they fit the qualities of a gas!