# Prologue

Physical science, which includes chemistry and physics, is usually thought of as the study of the nature and properties of matter and energy in non-living systems. A matter is the “stuff” of the universe — the atoms, molecules, and ions that make up all physical substances. The matter is anything that has mass and takes up space.

Energy is the capacity to cause change. Energy cannot be created or destroyed; it can only be conserved and converted from one form to another. “Potential energy” is the energy stored in an object due to its position — for example, a bucket of water balanced over a doorway has the potential to fall. “Kinetic energy” is energy that is in motion and causing changes. Any object or particle that is in motion has kinetic energy based on its mass and speed. Kinetic energy can be converted into other forms of energy, such as electrical energy and thermal energy.

There are five known phases, or states, of a matter: solids, liquids, gases, plasma and Bose-Einstein condensates. The main difference in the structures of each state is in the densities of the particles.

Solids

In a solid, particles are packed tightly together so they are unable to move about very much. Particles of a solid have very low kinetic energy. The electrons of each atom are in motion, so the atoms have a small vibration, but they are fixed in their position. Solids have a definite shape. They do not conform to the shape of the container in which they are placed. They also have a definite volume. The particles of a solid are already so tightly packed together that increasing pressure will not compress the solid to a smaller volume.

Liquids

In the liquid phase, the particles of a substance have more kinetic energy than those in a solid. The liquid particles are not held in a regular arrangement but are still very close to each other so liquids have a definite volume. Liquids, like solids, cannot be compressed. Particles of a liquid have just enough room to flow around each other, so liquids have an indefinite shape. A liquid will change shape to conform to its container. Force is spread evenly throughout the liquid, so when an object is placed in a liquid, the liquid particles are displaced by the object.

The magnitude of the upward buoyant force is equal to the weight of the fluid displaced by the object. When the buoyant force is equal to the force of gravity pulling down on the object’s mass, the object will float. This principle of buoyancy was discovered by the Greek mathematician Archimedes who, according to legend, sprang from his bath and ran naked through the streets shouting “Eureka!”

Particles of a liquid tend to be held by weak intermolecular attraction rather than moving freely as the particles of a gas well. This cohesive force pulls the particles together to form drops or streams.

Scientists reported in April 2016 they had created a bizarre state of matter, one that had been predicted to exist but never seen in real life. Though this type of matter could be held in one’s hand as if it were a solid, a zoom-in on the material would reveal the disorderly interactions of its electrons, more characteristic of a liquid. In the new matter, called a Kitaev quantum spin liquid, the electrons enter into a sort of quantum dance in which they interact or “talk” to one another. Usually, when matter cools down the spin of its electrons tends to line up. But in this quantum spin liquid, the electrons interact so that they affect how the others are spinning and never align no matter how cool the material gets. The material would behave as if its electrons, considered indivisible, had broken apart, the researchers reported April 4, 2016, in the journal Nature Materials.

Gases

Gas particles have a great deal of space between them and have high kinetic energy. If unconfined, the particles of a gas will spread out indefinitely; if confined, the gas will expand to fill its container. When a gas is put under pressure by reducing the volume of the container, the space between particles is reduced, and the pressure exerted by their collisions increases. If the volume of the container is held constant, but the temperature of the gas increases, then the pressure will also increase. Gas particles have enough kinetic energy to overcome intermolecular forces that hold solids and liquids together, thus a gas has no definite volume and no definite shape.

Plasma

Plasma is not a common state of the matter here on Earth but may be the most common state of matter in the universe. Plasma consists of highly charged particles with extremely high kinetic energy. The noble gases(helium, neon, argon, krypton, xenon, and radon) are often used to make glowing signs by using electricity to ionize them to the plasma state. Stars are essentially superheated balls of plasma.

Bose-Einstein condensates

In 1995, technology enabled scientists to create a new state of matter, the Bose-Einstein condensate (BEC). Using a combination of lasers and magnets, Eric Cornell and Carl Weiman cooled a sample of rubidium to within a few degrees of absolute zero. At this extremely low temperature, molecular motion comes very close to stopping altogether. Since there is almost no kinetic energy being transferred from one atom to another, the atoms begin to clump together. There are no longer thousands of separate atoms, just one “super atom.” A BEC is used to study quantum mechanics on a macroscopic level. Light appears to slow down as it passes through a BEC, allowing the study of the particle/wave paradox. A BEC also has many of the properties of a superfluid — flowing without friction. BECs are also used to simulate conditions that might apply in black holes.