To understand what matter is, we first must comprehend the three different states that it can exist in. Those three physical states are solids, liquids, and gases. A good example to illustrate this is water. Water, in its solid state is ice, in its liquid state is liquid water, and in its gaseous state is steam.
Solids usually have a definite shape and a definite volume. However, when a solid is broken into smaller pieces it is not changed chemically. For example if you crush an aspirin into a power it is still a solid just in smaller pieces.
Now we have the problem of distinguishing between a liquid and a gas. What makes a liquid different from a gas is the characteristic of compressibility. A gas is easily compressible, where a liquid is not. Say for instance that you have a piston within an enclosed tube. If the tube is filled with steam, and then the piston is compressed, it is easy to compress the steam with the piston. As a result, the piston travels far into the tube. Now we put water into the enclosed tube. It is not nearly as easy to push the piston down into the tube now. Why? Well, a liquid is a lot harder to compress than a gas. This is because the molecules in the gas are farther apart than the molecules in the liquid.
These two characteristics that we have
discussed, how rigid an object is, and an object's ability to be
compressed, are used to determine the three basic states of matter
A solid is a form of matter which is made distinct by it rigidity. That
is, a solid has a fairly fixed volume and shape, and is harder to compress
than a gas or a liquid.
A liquid is a form of matter that is a fairly incompressible. This means
that a liqiud basically has a fixed volume, but not a fixed shape. It
takes the shape of its container.
A gas is an easily compressible fluid. This means that a given quantity of
gas will fit into a container of any size and shape. A gas has neither a
definite volume nor a definite shape.
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