What is chemistry?

About chemical bonds and structures

Our world is made from atoms. Atoms consist of a kernel consisting again  of positively charged protons and uncharged neutrons, and a cloud of surrounding negatively charged electrons moving about the kernel. Positive and negative charges attract each other, and therefore an atom is hold together.

However, it is possible for electrons to be situated in such a way between atoms that they attract the kernal of two or more atoms. Such electrons will attract the atoms together.

Some atoms attract by themselves electrons, so that the atom gets negatively charged. Other atoms by themselves pull electrons away, and get positively charged. A negatively and a positively charged atom will attract each other.

These two attractment effects, alone or blended together, can effectively bind two or more atoms together, or making a chemical bond. Usually a bond consists of two electrons making an attraction effect.

Units of atoms bound together are often just small and equally composed. If so the units of atoms bonded together are called molecules. In other cases they can be larger, but still equally sized and composed. THese will also usually be called molecules.

In other cases, the units are composed of atoms arranged in a regular fashion, but can be of any size, and are most often very great with billions of atoms in each unit. Techically such units are giant molecules, but they are usually called crystals, or corns or something similar. A diamant is a typical example of such giant molecule or crystal. Metals are also composed of such crystals, and these are usually called corns.

Even though a compound consist of small equally sized molecules, these mulecules can glue together in a regular fashion and make objects with a regular shape. Such objects are also called crystals. An example is a sugar crystal.

And crystals can glue themselves together to even greater objects, like for example stons in rocks.

There are several kinds of bonds:

Covalent bonds: In such a bond, the shared electrons are equally distributed between the atoms.

Polar covalent bonds: By these bonds, one atom attract electrons by itself to some degree and another repels electrons by itself to some degree. The atoms then get some degree of opposite charges and will attract each other by an ectrostatic forc. Electrons will also to some degree situate themselves between the two kernels and attract both the two atom  kernels, and also this way bond the atoms together.

Ion bonds: Here on of the atoms repell some electrons totally by itself, and the other attracts the same electrons totally. The electrons will not be shared, but the positively sharged atom and the negatively charched atom will attract each other.

Metallic bonds: Here electrons are free to move around many atoms in a crystal, and will often be situated between the kernels. They thus hold the atoms together, and because they can move around, they can lead electric current.

In a chemical process, the bonds between the atoms in compounds are broken and the atoms are composed together in a new fashion.

To brake bonds, and make new bonds often require  energy because the products contains more energy than the iniial compounds contain.  This energy is supplied by heating, by radiation with light, by microwaves or other means. Such a process requiring energy, is called an endothermic process.

In other cases the result of the process, or reaction, has much less energy that the raw materials. In these cases, the process will go on by its own without furnished energy during the process, and produce heat. Such a process is called exothermic. However, the process often have to be feeded with some energy to begin with. This is because the chemical bonds will have to be stretched before they are broken, and this stretching requires energy. But when the process has initiated, it leaves so much energy free, that the necessary stretching occurs of its own. Fire, or combustion is a typical example of such a process. You often have to lit up the fire, but once lit up, it continues of its own.

The chemicals that react during a chemical process and the result of the process can be in several physical conditions, or aggregate conditions, of which the main types are solids compounds, liquids or gasses

Solid compounds: In a solid compound, the forces between the molecules or atoms are so strong that the molecules are held together in one piece, and the molecules or atoms are locked gainst each other so that a piece keeps its form even though it is influenced by external forces, as long as the force does not exceed a certain size characteristic of the compound.

Liquids: In a liquid the forces between the molecules are great enough to keep the molecules of a substance to escape away from each other, but the forces do not lock the molecules rigidly against each other, so the molecules can easily slide between each other. Therefore a liquid does not keep a  permanent shape and will float out on a surface because of the gravitation.

Gasses: In a gas there are not enough forces between the molecules to hold them together. Any pressure or external force will keep a piece of gas to inflate and go apart in all directions. Therefore a gas must be held in a locked container or something acting like a container. The air is a gas, and this gas is held in place around the earth by gravity.

This simple theory of matter conditions is an over-simplified picture. Many things in nature and daily life behave in a way that is different from this description. For example a thread or a piece of fabric that behave nearly as a liquid upon forces in some directions and as a very solid thing upon forces in other directions so that a piece allways is held together and so that the toporaphy of the piece allways is intact. The topography of an object describes what parts of an objects that are fastened to each other.

Anoter example of a thing that neither is a liquid nor a solid in the strict sense is a robber band. It can be stretched until a certain limit, but at that limit it behaves very much like a solid object, and the topography of the rubber band is allways intact, but apart form this, the rubber band does not have a permanent form.

During a chemical reaction, the reacting the substance can change aggregate state in a lot of ways. Solids liquids or gasses can produce both solids, liquids and gasses as a product, or something that cannot be described as neither of these.

About chemical reactions

During a chemical reaction chemical bonds are broken, and then new bonds are formed between the broken pieces of the original molecules. But usually new bonds are formed between other pieces than those hold together originally. Thus new compounds are formed.

In order to brake bonds, energy must be suppied. The energy gives power to overwhelm the attractive forses in the bonds. The energy can be supplied by heat, by light or by electricity, dependent upon the type of reaction.

When the new bonds are formed, energy is released. If the released energy is greater than the energy supplied to break the original bonds, the reaction produces enery. Such a reaction will produce heat, light or an electric current, and such reactions will often proceed by themselves when it has begun. Such a reaction is called exoterm.

Other reactions need more energy to break the original bonds that the energy released when new bonds are formed. Such a reaction must allways have a continuous supply of energy to proceed. Such reactions are called endoterm reactions.

About oxidation, reduction and fire

Originally oxidation simply denoted a process where oxygen makes bond with another substance. One used to say that the other substance got oxidized.

Reduction originally ment freeing a substance from a bond to oxygen. An example is the reduction of metal ore to make free metals.

When oxygen makes bonds, electrons tend to be pulled towards the oxygen atom so that the oxygen gets negatively loaded, and the other substance positively loaded. When oxygen bonds another substance, polar covalent or ionic bindings are thus formed.

Nowadays the term oxydation  is used in a wider sense. Oxidation is defined as any chemical process that results in electrons being pulled away from  an atom. This atom is said to be oxidized.

Reduction is defined as any chemical process in which elactrons are pulled towards an atom so that the atom gets negatively loaded.

Reduction and oxidation allways occur together, when one atom gets reduced, another gets oxidized. A process where reduction or oxidation occur is called a redox-process.

In the special case where oxygen binds to a substance, the substance is oxidized and oxygen is reduced.

Another special case is when a halogen, as for example chlorine, binds to some substance. The substance is also then oxidized, and the halogen is reduced. Clorine can for example bind to hydrogen to form HCL, or hydogen chloride, or chlorine can bind to the metal sodium to form NaCl or ordinary salt.

When two substances bind together in a redox-process, much energy tend to be released as heat. The heat can be so intense that the blending of substances begin to glow.

If a chemical process releases so much energy that the products are glowing, and some or all of the products are gasses, these glowing gasses will pour out from the reaction site and ascend up into the air. Such glowing gasses comming out of some process are called flames.

Any chenical or physical process that produces glowing gasses, or flames, is called fire.

When two substances of which one is in an oxidized state and the other in a reduced state, shall be separeted, much energy must usually be supplied, usually in the form of heat or electricity.

Such an example is when a free metal shall be produced from the ore. Then the ore must be heated, so that the binding between the oxidized metal and the reduced substance (usually oxygen) can be broken.  In addition a helping substance (a so-called reducer)  that the can take over the binding and thus be oxidixed instead is usually necessary. Carbon is often used as such a substance.