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# Understanding "Solid"

At first, the word "solid" may seem simple, but when it comes to rocks and minerals, it can be tricky.

To explore this, we will use the same materials that we used to explore "naturally occurring." You will need as many of the items from the following list as you can find:

• several mineral specimens
• several rock specimens
• coins, bone, teeth, sea shells, wood, nails, cloth, glass, feather, paper, water, salt, pepper, other objects made of different materials

We are using the word "solid" to talk about a phase or state of matter. Both rocks and minerals must be solid. The common states of matter are solid, liquid, gas, and plasma (although your textbook may not mention plasma.) That seems simple enough, so lets look at some examples.

In the photograph above, look at the bottle of water in the upper, right hand corner. Is the water a solid? No, of course not, It is a liquid. Think about other liquids, such as milk, oil, or soda. They all stay the same size, but take on the shape of their container. Pour them into a round container, and they take on a round shape. Pour them into a square container, and they take on the square shape.

Next look at the metal bolt that are just below the bottle of water. It is a liquid? No, it is solid. It keeps its same size and shape, no matter what shape container you put it in. See, this is simple.

### Just below, and slightly to the left of the bolt is a small dish of dirt. Is dirt a solid?

Hmmm. If you pour it into a round container, it takes on the round shape. If you pour it into a a square container, it takes on a square shape. Does that mean that dirt is a liquid? No. Instead, dirt is made up of many tiny pieces of solid material. While the pile of dirt seems to take on the shape of its container, if you examined it under a microscope, you would see that the tiny pieces of dirt have not changed their shape. They are solid. In the same way, if you had a huge pile of bolts, it would act like the dirt does. You could pour the bolts into different shaped containers, and they would shift to fill the shape, but the individual bolts would not change their shape. The bolt and the dirt are both solids.

### Looking at the left side of the photograph, we see another challenge. It is a piece of red cloth with yellow and blue stripes. Is cloth solid?

Once again, if we stuff the cloth into a container, it will change its shape, but again, if you look at it under a microscope, the threads have not changed. The threads of the cloth are just like the tiny particles of the dirt. The cloth is a solid.

With the tricky examples, it may help to ask yourself, "Is this a liquid?" To most people, cloth and dirt are obviously not liquids (like water), gases (like the air around you) or plasma (like a lightning bolt.) The only other common state of matter is solid. It can also help to examine the material with a magnifying glass or microscope to let you see the individual pieces.

To learn even more about solids and other states of matter, you may want to check out this video: Egg States