What are chemical reactions?
Chemical reactions occur whenever bonds are formed or broken between molecules. Why certain atoms combine with which other atoms is a complex question which is explained exhaustively by quantum chemistry. The simple version is that atoms bond together electromagnetically based on the properties of their electron shells. There are various types of chemical bonds; in general, the more closely overlapping the electron shells are, the stronger the bond is. Chemical reactions happen when heat, radiation, and/or foreign chemicals disturb an equilibrium condition and cause the breakage and/or formation of chemical bonds, thereby giving rise to new molecular forms. Chemical reactions can be classified into a few categories. The simplest is probably synthesis, where two or more molecules or atoms combine into a new molecule. For example, iron plus oxygen forms iron oxide, or rust. The opposite of synthesis is analysis, or chemical decomposition, where a molecule breaks apart into its constituen
Chemical reactions are processes in which one or more reactants are converted into products through a chemical change involving the breaking and reforming of chemical bonds. During a chemical reaction, the substances are converted into new substances which may exhibit totally different chemical properties than the original reactants. Mass is always conserved in purely chemical reactions, the mass of the reactants at the star of the reaction will always equal the mass of products produced at the end of the reaction. The total number of atoms involved in a reaction is also conserved meaning that even though atoms in molecules may be in completely new bonds after the reaction is complete, the total number of particles will be the same. Chemical reactions must be balanced due to the fact that mass and the number of particles are conserved throughout the reaction. Take the following reaction for example; Hydrogen gas reacts with Oxygen gas to form water, H2 + O2 → H2O Notice that there are
A chemical reaction is when two or more substances bond together as a result of the exchange or sharing of electrons (i.e., ionic or covalent bonds). There is a lot more I could say in terms of all the types of bond and what exactly happens, but that is my brief answer. In terms of being able to TELL if a reaction is chemical (as opposed to physical), there are some indications. For one ask yourself if the reaction is REVERSIBLE. For example, when water changes to ice, you can reverse this so, this is a PHYSICAL change or reaction. Making a cake, however, is the result of a chemical reaction. Other indicators of a chemical reactions are : color change, the release of heat, the release of light (e.g., fire), a loud sound, a sudden decrease in temperature. None of these tell you FOR SURE that something is a chemical change, but they are very good indicators.
