The freezing point and the melting point are said to be the same, because any increase in temperature from that point will cause the substance to melt, while any drop in temperature will cause it to freeze. Likewise, the vaporization and condensation points (or the sublimation and desublimation points) always match. In most substances, as the pressure increases, the vaporization/condensation point also increases, or vice versa. For example, the boiling point of water decreases as you go up a mountain, because the air pressure is lower. The relationship for freezing and melting can go in different directions depending on the substance.
Many other states of matter can exist under special conditions, including strange matter, supersolids, and possibly string-net liquids. Scientist work on experiments at very high or very low temperatures to learn more about phases of matter.
Bose-Einstein condensates and fermionic condensates are phases of matter that apply to particles called bosons and fermions, respectively. (More than one boson can exist in the same spot at the same time. Only one fermion can exist in the same spot at the same time). Bose-Einstein condensates and fermionic condensates occur at incredibly low temperatures. All of the particles in these condensates begin to act like one big quantum state, so they have almost no friction or electrical resistance.
When the core of a star runs out of light elements (like hydrogen or helium) to sustain fusion, the core will collapse into a very dense state called "degenerate matter". Everything is packed very tightly and can barely move. If the star isn't too heavy, it becomes a white dwarf. In a heavier star, the pressure is so intense that even the protons and electrons are crushed, and it becomes a neutron star.
The protons and neutrons that make up atoms are made of even smaller things called quarks (which are "glued" together by things called "gluons"). At incredibly high temperatures over 2 trillion Kelvin, quarks and gluons turn into another state of matter. Humans can make a little bit of quark-gluon plasma in the Large Hadron Collider at CERN, but it doesn't last long before cooling down.
When a substance has enough temperature and pressure at the same time, called the critical point, you can't tell the difference between very dense gas and very energetic liquid. This is a supercritical fluid, and it behaves like both liquid and gas.
Superfluids, on the other hand, only happen at very low temperatures, and only for a few special substances like liquid helium. Superfluids can do things that regular liquids cannot, like flowing up the side of a bowl and getting out.
Perimeter
In geometry, perimeter is the distance around a flat object. For example, all four sides of a square rhombus have the same length, so a rhombus with side length 2 inches would have a perimeter of 8 inches (2+2+2+2=8).
For a polygon, the perimeter is simply the sum of the length of all of its sides. For a rectangle, the perimeter is twice the sum of its length and width (formula_1). Perimeter can also be calculated for other planar figures, such as circle, sector and ellipse.
Real-life objects have perimeters as well. A football field, including the end zones, is 360 feet long and 160 feet wide. This means that the perimeter of the field is 360+160+360+160=1040 feet.
The perimeter of a circle is usually called the circumference. It may be calculated by multiplying the diameter times "Pi". Pi is a constant which is approximately equal to 3.14159; however, the places to the right of the decimal are endless. The number of places used depends on the accuracy required for the result.
Nation
A nation is a group of people who share the same culture, history, language or ethnicity. It can also be described as people living in the same country and government.
The word "nation" comes from a Latin language word meaning "birth" or "place of birth." The adjective is national.
Some nations are people with a particular belief, such as the Vatican City, or ethnic group, such as Armenia. Others share an idea, such as Democracy in the United States or Communism in China.
Some nations are controlled by a small minority who have all the power, such as Saudi Arabia, who hold the nation together with the use of this power.
Some of these may also be combined. The highest lawful authority of most nations is a constitution, which is a document which states clearly what kinds of power the rulers have and how new laws must be made. Many others are ruled by a single person who holds an "office" (position), such as a King or Pope, or from a long legal tradition without an official Constitution, such as the United Kingdom.
Matrix
Matrix can mean:
Metal
Some chemical elements are called metals. They are the majority of elements in the periodic table. These elements usually have the following properties:
Most metals are solid at room temperature, but this does not have to be the case. Mercury is liquid. Alloys are mixtures, where at least one part of the mixture is a metal. Examples of metals are aluminium, copper, iron, tin, gold, lead, silver, titanium, uranium, and zinc. Well-known alloys include bronze and steel.
The study of metals is called metallurgy.
Most metals are hard, shiny, they feel heavy and they melt only when they are heated at very high temperatures . Lumps of metal will make a bell-like sound when they are hit with something heavy (they are sonorous).
Heat and electricity can easily pass through a metal (it is conductive). A lump of metal can be beaten into a thin sheet (it is malleable) or can be pulled into thin wires (it is ductile). Metal is hard to pull apart (it has a high tensile strength) or smash (it has a high compressive strength). If you push on a long, thin piece of metal, it will bend, not break (it is elastic). Except for cesium, copper, and gold, metals have a neutral, silvery color.
Not all metals have these properties. Mercury, for instance, is liquid at room temperature, Lead, is very soft, and heat and electricity do not pass through iron as well as they do through copper.
Metals are very useful to people. They are used to make tools because they can be strong and easy to shape. Iron and steel have been used to make bridges, buildings, or ships.
Some metals are used to make items like coins because they are hard and will not wear away quickly. For example, copper (which is shiny and red in color), aluminium (which is shiny and white), gold (which is yellow and shiny), and silver and nickel (also white and shiny).
Some metals, like steel, can be made sharp and stay sharp, so they can be used to make knives, axes or razors.
Rare metals with high value, like gold, silver and platinum are often used to make jewellery. Metals are also used to make fasteners and screws. Pots used for cooking can be made from copper, aluminium, steel or iron. Lead is very heavy and dense and can be used as ballast in boats to stop them from turning over, or to protect people from ionizing radiation.
Many things that are made of metals may, in fact, be made of mixtures of at least one metal with either other metals, or with non-metals. These mixtures are called alloys. Some common alloys are:
People first began making things from metal over 9000 years ago, when they discovered how to get copper from its []ore. They then learned how to make a harder alloy, bronze, by adding tin to the copper. About 3000 years ago, they discovered iron. By adding small amounts of carbon to iron, they found that they could make a particularly useful alloy – steel.
In chemistry, metal is a word for a group of chemical elements that have certain properties. It is easy for the atoms of a metal to lose an electron and become positive ions, or cations. In this way, metals are not like the other two kinds of elements - the nonmetals and the metalloids. Most elements on the periodic table are metals.