How many states of matter are there? What are the names and characteristics of each?

Students, particularly younger students often give the answer 50 to the first question. I use this as an opportunity to mention that often there are several meanings for the same word in English; therefore, it is important that scientists pay close attention the meaning of words. The word "state" has several meanings in English.

An answer to the first question of either 3 or 4 is acceptable. The correct answer depends on the level and the expectations of the curriculum.

Solids have a definite volume and definite shape.

What does the word "definite" mean?

Liquids have definite volume, but take on the shape of their container.

How do you know that liquids take on the shape of their container?

Gases take on both the shape and the volume of their container.

How do you know that gasses like air, for example, take on the shape of their container, the room, for example?

Other remarks:

The fourth state of matter that is often recognized is:

Plasmas have all of the properties of a gas plus they conduct an electrical current.

I have neon and carbon dioxide spectral tubes that I bring as well as a fluorescent light bulb. Neon signs and fluorescent light bulbs are examples of plasmas that take advantage of the fact that plasmas often also emit light in addition to conducting an electrical current. However, light emission is not a necessary property. We can not touch plasmas because the have a very high energy and would burn flesh.