Chemical Reactions/Chemical Changes
In a Chemical Reaction, the Chemical Formula of the compound(s) undergoing the change are altered. As an example, a chemical change is gasoline burning, because the gasoline changes from its original structure into new compounds (such as carbon dioxide). Likewise, a physical change would be melting plastic. The plastic's chemical formula remains the same, but the shape and appearance of the plastic may be different.
There are several different categories of Chemical Reactions. The to basic types are Endothermic and Exothermic. Endothermic means that the reaction requires a constant input of energy to progress, while Exothermic means that it can go on by itself after the activation energy is put into it. An example of an exothermic reaction would be burning paper. Once you light the match which catches the paper on fire, thus providing the activation energy, the paper continues to burn by itself by reacting with they oxygen in the air until the paper is consumed. The reason that all paper doesn't spontaneously burst into flames is that the activation energy of the match was required to start the process of the burning (also called a combustion reaction) which produced its own heat and allowed more paper to burn. An example of an endothermic reaction is electrolysis. In electrolysis, an electric current is run through a water solution which causes the water to break down into Hydrogen gas (H2) and Oxygen gas (O2). As soon as the current through the wire is stopped, the reaction stops because the input of energy into water stops. That is the difference between endothermic and exothermic reactions. Most of the time, an exothermic reaction produces heat of its own which fuels the rest of the reaction.
There are also several different types of chemical reactions based upon the types of compounds undergoing the reaction and the ways in which they react. These include, Ionic (AKA Double Displacement), Single Displacement, Synthesis, Decomposition, Combustion, and Acid-Base.
There are several different categories of Chemical Reactions. The to basic types are Endothermic and Exothermic. Endothermic means that the reaction requires a constant input of energy to progress, while Exothermic means that it can go on by itself after the activation energy is put into it. An example of an exothermic reaction would be burning paper. Once you light the match which catches the paper on fire, thus providing the activation energy, the paper continues to burn by itself by reacting with they oxygen in the air until the paper is consumed. The reason that all paper doesn't spontaneously burst into flames is that the activation energy of the match was required to start the process of the burning (also called a combustion reaction) which produced its own heat and allowed more paper to burn. An example of an endothermic reaction is electrolysis. In electrolysis, an electric current is run through a water solution which causes the water to break down into Hydrogen gas (H2) and Oxygen gas (O2). As soon as the current through the wire is stopped, the reaction stops because the input of energy into water stops. That is the difference between endothermic and exothermic reactions. Most of the time, an exothermic reaction produces heat of its own which fuels the rest of the reaction.
There are also several different types of chemical reactions based upon the types of compounds undergoing the reaction and the ways in which they react. These include, Ionic (AKA Double Displacement), Single Displacement, Synthesis, Decomposition, Combustion, and Acid-Base.
- In a Synthesis Reaction, two or or more reactants are combined to form a product. An example is Carbon and Oxygen (O2) combining to form Carbon Dioxide (CO2). This is one of the most common types of reaction and is used to make more complicated and larger compounds out of smaller, simpler compounds. The general form of these equations is A + B -> AB.
- In a Single Displacement reaction, an element and an compound to form a different compound and a different element. This happens when the element by itself in the reactant side of the equation, which is more reactive than the element bonded to the compound in the reactants, "kicks out" the element from the compound, putting itself in its place and leaving the "kicked-out" (displaced) element by itself. An example of this reaction is Zinc and the hydrogen in Hydrochloric Acid (HCl) swapping places to form Zinc Chloride and Hydrogen gas. The general form for these equations is A + BC -> B + AC.
- In an Ionic (Double Replacement) reaction, two ionic compounds swap parts for form two new ionic compounds. An example of this is Sodium Hydroxide (NaOH) + HCl (Hydrochloric Acid) -> NaCl (Sodium Chloride, AKA table salt) + H2O (Water, in case you didn't know). The general form for this reaction type is AB + CD -> AC + BD.
- In a Decomposition Reaction, one reactant breaks down into two or more products. These types of reactions are usually endothermic or require a catalyst to speed up their progress. An example is Hydrogen Peroxide (H2O2) decomposing into Water and Oxygen (O2). The general form for a decomposition reaction is AB -> A + B. It is essentially the opposite of a synthesis reaction.
- In a Combustion Reaction, an oxidizing agent reacts with a fuel source in an exothermic reaction.
- In an Acid-Base Reaction, also known as a titration, both an acid and a base combine to form water and other compounds.