Gas
Definition 1 of 6
Pro Tip 1/3
Intangible substance
Understand that 'gas' refers to something you can't hold like solids. The helium gas inside balloons is lighter than air.
Pro Tip 2/3
Invisible but real
Remember gases may be invisible but they can have effects, like oxygen we breathe. Gas leaks can be dangerous even though you can't see them.
Pro Tip 3/3
Environmental impact
Some gases can contribute to environmental problems like global warming. Factories can emit harmful gases into the atmosphere.