The volume is definite if the temperature and pressure are constant. When a solid is heated above its melting point, it becomes liquid, given that the pressure is higher than the triple point of the substance.
Intermolecular or interatomic or interionic forces are still important, but the molecules have enough energy to move relative to each other and the structure is mobile. This means that the shape of a liquid is not definite but is determined by its container. The volume is usually greater than that of the corresponding solid, the best known exception being water, H 2 O. The highest temperature at which a given liquid can exist is its critical temperature.
The spaces between gas molecules are very big. Gas molecules have very weak or no bonds at all. A gas is a compressible fluid. Not only will a gas conform to the shape of its container but it will also expand to fill the container.
In a gas, the molecules have enough kinetic energy so that the effect of intermolecular forces is small or zero for an ideal gas , and the typical distance between neighboring molecules is much greater than the molecular size. A gas has no definite shape or volume, but occupies the entire container in which it is confined. A liquid may be converted to a gas by heating at constant pressure to the boiling point, or else by reducing the pressure at constant temperature.
At temperatures below its critical temperature, a gas is also called a vapor, and can be liquefied by compression alone without cooling. A vapour can exist in equilibrium with a liquid or solid , in which case the gas pressure equals the vapor pressure of the liquid or solid. A supercritical fluid SCF is a gas whose temperature and pressure are above the critical temperature and critical pressure respectively.
In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas, but its high density confers solvent properties in some cases, which leads to useful applications. For example, supercritical carbon dioxide is used to extract caffeine in the manufacture of decaffeinated coffee. This gives it the ability to conduct electricity. Like a gas, plasma does not have definite shape or volume. Unlike gases, plasmas are electrically conductive, produce magnetic fields and electric currents, and respond strongly to electromagnetic forces.
The plasma state is often misunderstood, but it is actually quite common on Earth, and the majority of people observe it on a regular basis without even realizing it. Lightning, electric sparks, fluorescent lights, neon lights, plasma televisions, some types of flame and the stars are all examples of illuminated matter in the plasma state.
A gas is usually converted to a plasma in one of two ways, either from a huge voltage difference between two points, or by exposing it to extremely high temperatures. Heating matter to high temperatures causes electrons to leave the atoms, resulting in the presence of free electrons. A state of matter is also characterized by phase transitions.
A phase transition indicates a change in structure and can be recognized by an abrupt change in properties. A distinct state of matter can be defined as any set of states distinguished from any other set of states by a phase transition.
Water can be said to have several distinct solid states. Likewise, ferromagnetic states are demarcated by phase transitions and have distinctive properties. When the change of state occurs in stages the intermediate steps are called mesophases. Such phases have been exploited by the introduction of liquid crystal technology.
The state or phase of a given set of matter can change depending on pressure and temperature conditions, transitioning to other phases as these conditions change to favor their existence; for example, solid transitions to liquid with an increase in temperature. Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point, boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms.
Forms of matter that are not composed of molecules and are organized by different forces can also be considered different states of matter. One place you can see plasmas in action is in a fluorescent light bulb or neon sign. In those cases a gas neon for signs is subjected to a high voltage, and the electrons are either separated from the atoms of the gas or pushed into higher energy levels.
The gas inside the bulb becomes a conductive plasma. The excited electrons that drop back into their previous energy levels emit photons — the light we see in a neon sign or fluorescent lamp. Plasma TVs work in the same way. A gas — usually argon, neon or xenon — is injected into a sealed gap between two glass panels. An electrical current is passed through the gas, which causes it to glow. The plasma excites red, green and blue phosphors, which combine to give off specific colors, according to eBay.
Another use for plasma is in plasma globes, which are full of noble gas mixes that produce the colors of the "lightning" inside them when an electric current ionizes the gas. Another example of plasma is in the auroras that surround the poles when the sun is particularly active. The solar wind is a stream of charged particles mostly protons , which hit Earth's magnetic field.
Those particles, being charged, follow magnetic field lines and move toward the poles, where they collide with and excite atoms in the air, mostly oxygen and nitrogen.
Like a neon sign, the excited oxygen and nitrogen atoms give off light. Follow LiveScience on Twitter livescience. Just a fraction above this temperature — and only for some elements — a BEC occurs. The atoms start behaving like little waves and start overlapping one another until they eventually act like one wave and essentially become a superatom. They are not bonded or mixed — they have become indistinguishable from one another, having the same qualities and existing in the same place. Daniel Kleppner from the Massachusetts Institute of Technology has a great description.
It is important to understand that matter exists in all states and that matter can also change states. It does this by either using or releasing energy, and it is usually associated with changes in temperature and pressure. A simple example is water. If you have a block of ice, you have solid water. Add heat a form of energy and the ice melts into liquid water that you could drink it has reached its melting point. Continue to apply heat, and the water will evaporate and turn into steam, which is water in a gaseous state it has reached boiling point.
This works backwards, too. Gas can cool down by losing energy and condense back into liquid water and cool down further into a solid. There is even a process called sublimation where a solid can turn straight into a gas when heat is applied. Slumpy solids or lumpy liquids explores a range of common household substances to determine if they have the properties of a solid, a liquid or both.
Exploring states of matter uses concept maps to explore current ideas about states of matter. Use this unit plan, aimed at middle primary, to experiment with various liquids, including non-Newtonian fluids, to see how their viscosity is changed by stress or force.
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