States of Matter
As a young kid, I remember staring in wonder at a pot of boiling water. Searching for an explanation for the bubbles that formed, I believed for a time that the motion of the hot water drew air down into the pot, which then bubbled back to the surface. Little did I know that what was happening was even more magical than I imagined ‐ the bubbles were not air, but actually water in the form of a gas. The different states of matter have long confused people. The ancient Greeks were the first to identify three classes (what we now call states) of matter based on their observations of water. But these same Greeks, in particular the philosopher Thales (624 ‐ 545 BCE), incorrectly suggested that since water could exist as a solid, liquid, or even a gas under natural conditions, it must be the single principal element in the universe from which all other substances are made. We now know that water is not the fundamental substance of the universe; in fact, it is not even an element. To understand the different states in which matter can exist, we need to understand something called the Kinetic Molecular Theory of Matter. Kinetic Molecular Theory has many parts, but we will introduce just a few here. One of the basic concepts of the theory states that atoms and molecules possess an energy of motion that we perceive as temperature. In other words, atoms and molecules are constantly moving, and we measure the energy of these movements as the temperature of the substance. The more energy a substance has, the more molecular movement there will be, and the higher the perceived temperature will be. An important point that follows this is that the amount of energy that atoms and molecules have (and thus the amount of movement) influences their interaction with each other. Unlike simple billiard balls, many atoms and molecules are attracted to each other as a result of various forces such as bonds. Atoms and molecules that have relatively small amounts of energy (and movement) will interact strongly with each other, while those that have relatively high energy will interact only slightly, if even at all, with others.
How does this produce different states of matter? Atoms that have low energy interact strongly and tend to “lock” in place with respect to other atoms. Thus, collectively, these atoms form a hard substance, what we call a solid. Atoms that possess high energy will move past each other freely, flying about a room, and forming what we call a gas. As you look at these pictures, think about these two big ideas which are always true when talking
about matter:
• Matter (solid, liquid, and gas) is made up of tiny particles called atoms and molecules.
• The atoms or molecules that make up matter are always in motion.
• These first two ideas make up a very important theory called the Kinetic‐molecular theory
of matter.
Another big idea is that:
The atoms or molecules that make up a solid, liquid or gas are attracted
to one another.
In a solid, the atoms are very attracted to one another. Because of this
strong attraction, the atoms are held tightly together. The attractions
are strong enough that the atoms can only vibrate where they are.
They cannot move past one another. This is why a solid keeps its shape.
In a liquid, the molecules are also in motion. The attractions between
the molecules in liquids are strong enough to keep the molecules close
to each other but not in fixed positions. Although the molecules stay
very near one another, the attractions allow the molecules of a liquid
to move past one another. This is why a liquid can easily change its
shape.
In a gas, the molecules are also moving. The attractions between the
molecules of a gas are too weak to bring the molecules together. This
is why gas molecules barely interact with one another and are very
far apart compared to the molecules of liquids and solids. A gas will
spread out evenly to fill any container. The molecules have so much energy they zoom or move around very quickly.
Plasmas are hot, ionized gases. Plasmas are formed under conditions of extremely high energy, so high, in fact, that molecules are ripped apart and only free atoms exist. More astounding, plasmas have so much energy that the outer electrons are actually ripped off of individual atoms, thus forming a gas of highly energetic, charged ions (atom with different number of proton and electrons). Because the atoms in plasma exist as charged ions, plasmas behave differently than gases, thus representing a fourth state of matter. Plasmas can be commonly seen simply by looking upward; the high energy conditions that exist in stars such as our sun force individual atoms into the plasma state.
As we have seen, increasing energy leads to more molecular motion. On the other hand, decreasing energy results in less molecular motion. As a result, one prediction of Kinetic Molecular Theory is that if we continue to decrease the energy (measured as temperature) of a substance, we will reach a point at which all molecular motion stops. The temperature at which molecular motion stops is called absolute zero and has been calculated to be ‐273.15 degrees Celsius(−459.67° Fahrenheit). While scientists have cooled substances to temperatures close to absolute zero, they have never actually reached absolute zero. The difficulty with observing a substance at absolute zero is that to “see” the substance, light is needed, and light itself transfers energy to the substance, thus raising the temperature. Despite these challenges, scientists have recently observed a fifth state of matter that only exists at temperatures very close to absolute zero.
Bose‐Einstein Condensates represent a fifth state of matter only seen for the first time in 1995. The state is named after Satyendra Nath Bose and Albert Einstein who predicted its existence in the 1920’s. B‐E condensates are gaseous superfluids (fluid but resists being poured) cooled to temperatures very near absolute zero. In this weird state, all the atoms of the condensate attain the same atomic state and can flow past one another without friction. The molecules are moving extremely slow with very little energy to help them move. In a Bose‐Einstein condensate, the many overlapping atoms can be considered to be a single super‐atom, with all of its atoms sharing a single atomic state. Bose‐Einstein condensates are extremely fragile. The slightest interaction with the outside world can be enough to warm them past the condensate threshold, causing them to break back down into individual atoms again.
1.Define Matter.
2. Fill in the chart:
State of Matter
How are the atoms
arranged
Atom attraction?
How do the atoms move?
Super atoms (overlap)
Strong
Very little movement, but frictionless
Solid
Liquid
Gas
Plasma
Bose‐Einstein
3.Can it change it’s shape?
Solid‐
Liquid‐
Gas‐
4. Why were plasma and Bose‐Einstein the last states of matter to be discovered?
5. Which phase/state of matter would be considered most dense? Why?
6. Which phase of matter would be considered least dense? Why?