States of Matter

http://www.chem4kids.com/files/matter_states.html

There are five main states of matter. Solids, liquids, gases, plasmas, and Bose-Einstein condensates (BEC) are all different states of matter. Each of these states is also known as a phase. Elements and compounds can move from one phase to another when specific physical conditions are present. One example is temperature. When the temperature of a system goes up, the matter in the system becomes more excited and active. Scientists say that it moves to a higher energy state. Generally, as the temperature rises, matter moves to a more active state.

Think about it this way. Remember that glass of water (H₂O) we talked about? When the temperature of the water goes up, the molecules get more excited and bounce a lot more. If you give a liquid water molecule enough energy, it escapes the liquid phase and becomes a gas. Have you ever noticed that you can smell a turkey dinner after it starts to heat up? As the energy of the molecules inside the turkey heat up, they escape as a gas. You are able to smell those volatile gas molecules.

A " phase " describes a physical state of matter. The key word to notice is physical. Things only move from one phase to another by physical means. If energy is added (like increasing the temperature) or if energy is taken away (like freezing something), you have created a physical change.

A compound or element can move from one phase to another, but still be the same substance. You can see water vapor, in the form of steam, over a boiling pot of water. That vapor (or gas) can condense and become a drop of water. If you put that drop in the freezer, it would become a solid piece of ice. No matter what phase it was in, it was always water. It always had the same chemical properties. On the other hand, a chemical change would change the way the water acted, eventually making it not water, but something completely different. If you added a carbon (C) atom to a water molecule, you would have formaldehyde (H₂CO), and that is nothing like water.

STATES OF MATTER http://www.edinformatics.com/math_science/states_of_matter.htm Everything on Earth can be explained in terms of 4 states (phases) of matter-- solid, liquid, gas, and plasma. What are the properties of a solid? A substance in a solid phase is relatively rigid, has a definite volume and shape. The atoms or molecules that comprise a solid are packed close together and are not compressible. Because all solids have some thermal energy, its atoms do vibrate. However, this movement is very small and very rapid, and cannot be observed under ordinary conditions. What are the different types of solids? There are four types of crystalline solids --

Ionic solids- - These substances have a definite melting point and contain ionic bonds. An example would be sodium chloride (NaCl). View the 3-D structure of a salt crystal.

Covalent solids -- These substance appear as a single giant molecule made up of an almost endless number of covalent bonds. An example would be graphite. View the 3-D structure of graphite).

	Molecular solids are represented as repeating units made up of molecules. An example would be ice. View the 3-D structure of ice.
	Metallic solids are repeating units made up of metal atoms. The valence electrons in metals are able to jump from atom to atom.

Amorphous solids

Amorphous solids do not have a definite melting point or regular repeating units. An amorphous solid is a solid in which there is no long-range order of the positions of the atoms unlike those in crystalline solids. An example of an amorphous solid is window glass. In addition many polymers such as polystyrene are amorphous.Amorphous solids can exist in two distinct states, the 'rubbery' state and the 'glassy' state. The temperature at which they transition between the glassy and rubbery states is called their glass transition temperature or Tg.

Interesting Note on Solids: While no mass at all is an impossibility, aerogels seem to come pretty close. Aerogels are the lightest solids and have a density of 1.9 mg per cm3 or 1.9 kg/m3 (526.3 times lighter than water). Sometimes called frozen smoke, aerogels are open-cell polymers with pores less than 50 nanometers in diameter.

---

Дата добавления: 2015-11-14