Chemical Changes: Combustion

Combustion

What is combustion? It is the burning of a complex sequence of chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. In a complete combustion reaction, a compound reacts with an oxidizing element, such as oxygen or fluorine, and the products are compounds of each element in the fuel with the oxidizing element.

Rapid combustion is a form of combustion in which large amounts of heat and light energy are released, which often results in a fire. This is used in a form of machinery such as internal combustion engines. Sometimes, a large volume of gas is liberated in combustion besides the production of heat and light. The sudden evolution of large quantities of gas creates excessive pressure that produces a loud noise(explosion). Combustion need not involve oxygen. Hydrogen burns in chlorine to form hydrogen chloride with the liberation of heat and light characteristic of combustion.

In complete combustion, the reactant will burn in oxygen, producing a limited number of products. When a hydrocarbon burns in oxygen, the reaction will only yield carbon dioxide and water. When a hydrocarbon or any fuel burns in air, the combustion products will also include nitrogen. When elements such as carbon, nitrogen, sulfur, and iron are burned, they will yield the most common oxides. Carbon will yield carbon dioxide, nitrogen will yield nitrogen dioxide ,sulfur will yield sulfur dioxide and iron will yield iron oxide. However, a complete combustion is almost impossible to form. In reality, a wide variety of major and minor species will be present. For example, the combustion of methane in air will yield, in addition to the major products of carbon dioxide and water, the minor side reaction products carbon monoxide and nitrogen oxides.

Incomplete combustion occurs when there isn't enough oxygen to allow the fuel to react completely with the oxygen to produce carbon dioxide and water, also when the combustion is quenched by a heat sink such as a solid surface or flame trap. When a hydrocarbon burns in air, the reaction will yield carbon dioxide, water, carbon monoxide, pure carbon (usually in the form of soot or ash) and various other compounds.

Combustion is used in everyday's life. Whether is it cooking, running of machines, running factories, the use of combustion is everywhere.

Chemical Changes: Single Displacement

Single Displacement

In this type of reaction, one element replaces another in a compound. This happens in two situations:
1. When a metal displaces a metal
2. A non-metal displaces a non-metal

In most single displacement reactions there is an element and an ionic compound as reactants.

The general pattern is:

A + BC --> AC + B

element A displaces element B

A and B are elements

BC and AC are compounds

Double Displacement

Double Displacement is a biomolecular process involving the exchange of bonds between the two reacting chemical species, which results in the creation of products with similar or identical bonding affiliations. To illustrate, consider two chemical species, AB and CD, which react to give AD and CB:

AB + CD → AD + CB
These chemical species can either be ionic or covalent.

A neutralization reaction is a specific type of double displacement reaction. Neutralization occurs when an acid reacts with an equal amount of a base. A neutralization reaction creates a solution of salt and water.

On the next post, I will be talking about combustion.

Chemical Changes: Decomposition

Decomposition

Chemical decomposition is the seperation of a chemical compound into elements or smaller compounds. It can be defined as the opposite of a chemical synthesis, though it would be wrong to say that decomposition is the direct opposite of chemical synthesis. Chemical decomposition is often an undesired chemical reaction, though not always. The stability that a chemical compound ordinarily has is eventually limited when exposed to extreme environmental conditions like heat, radiation, humidity or the acidity of a solvent. The details of decomposition processes are generally not well defined, as a molecule may break up into a host of smaller fragments. There are 2 types of decomposition reactions, thermolysis and electrolysis

Thermolysis, also known as thermal decomposition, is defined as a chemical reaction in which a chemical substance breaks up into at least two chemical substances when heated. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. The decomposition temperature of a substance is the temperature at which the substance decomposes into smaller substances or into its constituent atoms. The following video will show the effects of thermal decompositon.

Electrolysis is the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes and separation of materials.The key process of electrolysis is the interchange of atoms and ions by the removal or addition of electrons from the external circuit. The required products of electrolysis are in some different physical state from the electrolyte and can be removed by physical process. The following video shows elctrolysis of water.

Electrolysis - Break Water Into Hydrogen And Oxygen - For more of the funniest videos, click here

Having understand decomposition, i will be moving on to single displacement.

Chemical Changes: Synthesis

Synthesis

As said in the video, a synthesis reaction is where "two or more substances combined to form a single product". A synthesis reaction is the formation of complex chemical compounds from simpler ones. Many substances that are important to daily life are obtained from synthesis. Chemists synthesise chemical compounds that occur in nature to gain better understanding of the structures. Synthesis also enables chemists to produce compounds that do not form naturally for research purposes.

Chemical compounds are made up of atoms of different elements, joined together by chemical bonds. A chemical synthesis usually involves the breaking of existing bonds and the formation of new ones. Synthesis of a complex molecule may involve a large number of individual reactions in sequence from available starting substances to the desired end product. Each step usually involves reaction at only one chemical bond in the molecule.

The reactions involved in chemical syntheses usually involve at least two different substances. However that may not always be the case. Some molecules will change into others solely under the effect of heat or exposure to radiation. When two or more different substances interact, they need to be brought into close proximity with one another. This is usually done by carrying out the syntheses with the elements or compounds in their liquid or gaseous states.

After defining synthesis, you may asked, how is synthesis important? Where is it used? Well, one of the most commonly known is photosynthesis. The following video will explain what is photosynthesis.

Photosynthesis is an important biological process on earth. By taking in carbon dioxide and giving out oxygen, it has transformed the world into the hospitable environment we know today. Directly or indirectly, photosynthesis fills our food requirements and many of our needs for fibre and building materials. The energy stored in petroleum, natural gas and coal all came from the sun via photosynthesis, as does the energy in firewood, which is a major fuel in parts of the world.

You see, synthesis is not as foreign to us as many will think. Synthesis is also used to mass produce many products in the industry. On my next post, I will be writing and sharing more knowledge on decomposition. Hold your thoughts until then.

CHem REsearch TOpic

What are the different types of chemical changes and how are they used in real life?

This is my research topic. I decide to do this topic because I do not really understand what is chemical changes. It would also be interesting to know how they are used to benefit us in real life.

Prior to my research, I found out that other than chemical changes, there is also a physical changes. Let me define what is chemical changes. Chemical changes refers to bonds broken and new bonds formed between different atoms. The breaking and forming of bonds takes place when particles of the original materials collide with one another. Simply put, Chemical change is observed when the composition of a substance changes.

However, physical change is different to chemical change. Physical changes occur when objects undergo a change that does not change their chemical nature and only involves in changing of physical properties. Simply put, a physical change does not change the composition of a substance. An example would be water. Water in itself is in liquid form. However when it freezes, it state changes into ice. Though it state changes, when it melts, it turns back into water again. This shows that there is no change to the compositon of the water even though it state changes.

Having define what is chemical change and the difference between chemical and physical change, I have also researched on the types of chemical reaction briefly. I would be focus on the 5 main types of chemical changes, mainly synthesis, decompositon, single displacement, double displacement and combustion. I found a video on the the following types of chemical changes and hope you enjoy it.

Now after viewing this video, we now have a basic understanding of the types of chemical changes. But a lot of questions are left unanswered. How did the two substances reacted with each other? Why did they react like that? My next post, however, will try to answer questions asked on synthesis.