A substance with LOW pH. The lower the pH, the higher the acidity level is. pH has a direct effect on how acidic a substance is. For an example, battery acid. Battery acid has a pH level of about 1. This means that battery acid is very acidic. A substance is concidered acidic when it dips below the neutral pH level of 7.
Solid has vibrating molecules that barely move to keep it's shape
liquid moves at an average speed and keeps it's volume but not it's shape
gases move quickly and all over the place so they don't have a shape or volume
plasma is the quickest moving and is like a gas