States of Matter

The form in which observable physical objects exist.

Matter is all around us. Matter is the air you are breathing. Matter is the computer you are reading from now. Matter is the stuff you touch and see. Everything is Matter.  And it is more. Matter is defined as anything that has mass and takes up space. Matter is found in 3 major states; solid, liquid, and gas.

So what is matter made of? All matter is made of atoms. Atoms are the smallest particle of matter. They are so small that you cannot see them with your eyes or even with a standard microscope. A sheet of paper is about a million atoms thick. Science has come up with a technology to identify atoms called a scanning tunneling microscope (STM) which uses electricity to map atoms. There is more about atoms later, but first let's learn about the three states of matter.

Matter that is composed of atoms packed tightly together are known as solids. You cannot walk through a solid wall. The matter is packed so tight that it prevents you from moving through it. Solids hold their shape at room temperature. The pencil that you left in the desk at school will still be the same shape when you return tomorrow.

Even in solids there is a small space between the atoms. Depending on how tight the atoms are packed determines the density of matter. This means that a one-inch block of wood is not as dense as a one-inch block of gold. There is more space between the atoms of the wood than the atoms of the gold.

Liquids do not hold their shape at room temperature. There is space between the atoms of a liquid and they move slightly all of the time. This allows you to stick your finger into water and pull it back out, letting the water fill back in where your finger once was. But when walking through the water in the swimming pool, you have to push the water out of the way ‐ this means that you feel the heaviness of the water. Liquids flow or pour and can take on the shape of a container. If the liquid is poured into a wider or narrower container, the liquid will take on that new shape. Liquids are affected by gravity. If you pour only half a cup of milk, the top half of the container would have no milk. Liquids cannot be handed to another person well without the container. Imagine going into a restaurant and asking for lemonade. What if the waiter just put the lemonade into your hands ‐ no glass or cup? Could you lay the lemonade on the table to drink in a few minutes? Even water in a river or a lake has a container ‐ the banks, the bottom, the shore ‐ they form the container.

Gases not only do not hold their shape at room temperature, they don't even stay put. Gases are always moving. There is so much space between the atoms in gas that you can move around in them easily. When you walk from one side of the room to the other, you have walked through a bunch of gases that make up our air. You barely even know they are there. Gases will take on the shape of their container and can be compressed into a smaller space. Like when we compress air into a balloon ‐ it fills out the balloon shape. Gases will fill up the space too. You don't see only half of the balloon filled with air ‐ the air is not as influenced by gravity as a liquid or a solid would be.

For a better understanding, take a look at these animations of the behavior of solids, liquids, and gases.

Matter can change from one state to another, but can still be the same substance. A change of state, also called a phase change, is a physical change from one state of matter to another, for example, from solid to liquid or from liquid to gas.

How does matter move from one phase to another? If the motion of the atoms is altered by pressure or temperature, the state can change too. By lowering the temperature of water, it can freeze into a solid--ice. By heating water, it can become steam which is a gas. Whether solid, liquid or gas ‐ water is still water.

Pressure can change matter from one state to another. Deep in the earth solids turn to liquids because the heavy weight of layers and layers of the earth push down on the solids causing them to turn to liquid magma. This is just one example of how pressure can change matter too.

Other matter changes too, but often only exists in two states or requires the help of humans and technology to move through all three phases. Water is the only matter on earth that can be found naturally in all three - solid, liquid, and gas.

An atom is made up of a nucleus of neutrons and protons ‐ even smaller particles than an atom. They are called subatomic particles. Electrons circle around this nucleus. Atoms tend to have the same number of electrons as the number of protons in the nucleus. This number is very significant. Each kind of atom has a different number of protons. For example: oxygen has 8 protons. That means it also has 8 electrons. The 8 is known as its atomic number. But gold has 79 protons and 79 electrons. If you wanted to know how many protons and electrons are found in any given atom, the Periodic Table of the Elements is the place to find out.

Matter is organized into elements.  There are about 100 different elements found on Earth.  The table only tells us about the atoms of the 100 or so elements found on the Earth. An element cannot be broken down into smaller components. Gold is not made of anything ‐ except the element gold. The smallest possible piece of gold is just gold. If it were any smaller it would be the subatomic particles ‐ protons, neutrons, and electrons.

Of these elements, some are solids like gold or silver. Others are gases like oxygen and hydrogen, and still others can be liquids like mercury. Of course, this is based on room temperature. If an element is heated or cooled, or if enough pressure is applied to the element that could change its state of matter.

I bet you can't find salt on the Periodic Table of the Elements. That's because salt is actually made of two elements; sodium and chloride. You can find both of those on the table. The sodium and chloride atoms of salt are linked together much like magnets can link together. We call this a compound. Water is a compound made of oxygen and hydrogen. Sugar ‐ the white stuff you put into cookies ‐ is made of carbon, hydrogen, and oxygen. Lots of the substances around us are compounds. From vinegar to household bleach to nail polish remover to baking soda to aspirin ‐ we use compounds all around our homes.

All matter has qualities about it that describe it scientifically. We call these properties. They can explain the physical or chemical qualities of a matter. Some of the ways that we describe matter are by its color, its shininess, and its state at room temperature or its odor, mass, temperature at which it changes states, electric conductivity, and flexibility are also properties of matter. These are different for each type of matter and can help scientists identify a matter.

We often talk about the three states of matter; solid, liquid, and gas. Most of the matter that we use is in one of those three forms. But there is another that we see and use and that we would have a hard time living without ‐ plasma. It is often called the fourth state of matter. Plasma is electrically charged, does not hold its shape, has a huge amount of energy, and is very difficult state to manipulate without a laboratory. Plasma can be found here on Earth in flames, lightning, and the polar auroras. The sun, the stars, and some other space events and objects are also made of plasma matter.

Did you know that there are more phases of matter? We aren't as familiar with them nor do we see them every day. Some exist only in theory, others can be reproduced in laboratories, some are so new that scientists are still figuring out the details and others might exist, but have not yet been found in nature. They include: quark-gluon plasmas, Bose-Einstein condensates, fermionic condensates, strange matter, liquid crystals, quantum spin liquid (QSL), superfluids, supersolids, and the paramagnetic and ferromagnetic phases of magnetic materials. New theories and discoveries are happening all of the time, so you'll have to keep studying your physical science to learn more about these states of matter.

The state of matter of an element or atom is based on its behavior at room temperature. But what exactly is room temperature? Room temperature refers to air temperature not being specifically heated or cooled. Usually between 20 to 25°C (68 to 77°F). While the actual temperature could be hotter or cooler than these figures, it simply means that the matter has not been placed in an oven or a freezer, but was left out in the room to attain the temperature of the rest of the room. If an ice cube was left out in the room for a period of time, it would melt and become liquid water. Water is a liquid at room temperature. A diamond, on the other hand, is a solid at room temperature and will not change state no matter how long it sits there.