What is substance?
Substance is a form of matter that has a rest mass. The presence of rest mass in a substance is its main difference from the field. The constituent parts of a substance are protons, neutrons (they form a nucleus) and electrons (rotate around this nucleus).
There are simple and complex substances. What is the substance simple? Such a substance consists of molecules of one element and during a normal chemical reaction does not give in to further decomposition. Examples of simple substances are iron, copper, oxygen, nitrogen, and others.
What is the substance difficult? This substance, having in its composition two or more elements of the periodic system, interconnected in a certain proportion. Examples of a complex substance (they are also called compounds) are water, calcium oxide, iron oxide, nucleic acids, proteins.
For each substance (both simple and complex) a certain set of specific properties is inherent, that is, objective characteristics that determine its individuality.The most characteristic physicochemical properties are such constants (constant values) - boiling point, melting point, density, color, hardness, parameters of the crystal structure, thermodynamic characteristics.
There is one more concept - materials. For example, leather, wood, brass, rubber. At first glance, they can be attributed to complex substances, but it is not. A material has some set of common properties by which it is recognized. Other properties may have different variations, which allows dividing the material into varieties. Take the wood, in which a different variety has its own density, color and smell. It can be either a light cork tree or a heavy iron tree that sinks in water.
The number of substances in nature can be infinitely large. All the time, more and more are added to their known number, both opened and synthesized by man.
- The most common substance is oxygen (49% in the earth's crust), the rarest is astatine (content in the earth's crust is 0.16 grams);
- the most dense substance is osmium (density 22,587 g / cm3;
- the lightest substance is hydrogen (density 0.543 g / cm3);
- the most refractory substance is tungsten (+ 3420 ° С);
- the most heat-resistant composite material can withstand + 10,000 ° C for some time.