What are some examples of Chemical Change?

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Chemical change.

Chemical changes occur almost all the time. The change that converts one substance into another is known as a chemical change. During a chemical change, the composition of the substance is changed. When a chemical change occurs new substances are formed through a reorganization of the atoms.  A chemical change is irreversible. An example of chemical change is the fireworks explosion. Chemical Changes are also called Chemical Reactions. The chemical reaction produces one or more products, which usually have properties different from the reactants and have different physical and chemical properties. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, and might need   some type of energy, viz. heat, light or electricity to initiate the reaction.


What is the History of Chemical reaction?

From the ancient times, chemical reactions such as combustion in the fire, fermentation and the reduction of ores to metals were observed. Greek philosophers invented early theories of conversion of materials. Later, Alchemists studied chemical transformations in the middle Ages. A German-Dutch alchemist, Johann Rudolph Glauber, generated hydrochloric acid and sodium sulfate by the chemical reaction of sulfuric acid and sodium chloride,in the  17th century. In 1746, chemical reactions  came into practice into the industry which permitted a significant production of sulfuric acid and sodium carbonate, correspondingly. During 1909–1910, the Haber –Bosch process was discovered for the synthesis of ammonia.

What happens during a chemical change?

A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. During the chemical change, these bonds are broken and are created between dissimilar atoms. The process of breaking and forming of bonds occurs while particles of the initial materials have a collision with each other. An example of a chemical change is the reaction between sodium hydroxide and hydrogen chloride to produce sodium chloride, or common salt. This is an example of a chemical change, as the end product is molecularly dissimilar from the initial molecules. Being highly exothermic, this reaction releases heat in the form of energy and also flames are produced. The atoms are reorganized and the reaction is supported by an energy change with new products produced during chemical reactions. Change in state of certain chemicals is not possible, due to the shortage of heat in the exothermic reactions.


What are some indications of chemical change?

  • Change in temperature: In order to break chemical bonds, energy is needed. Also energy is released when new chemical bonds form. When the reaction involves more bond-breaking than bond making, the energy required is often absorbed from the surroundings, making them cooler. When there is more bond-making than bond-breaking, the excess energy is released, making the surroundings hotter.
  • Change in smell or taste: Chemical reaction changes the smell or taste of the substance. As, many chemical reactions have poisonous reactants or products, this method of detecting chemical change is not recommended.
  • Change in any distinctive chemical or physical property: If a property really differentiates that compound from all the others, there will be a change during reaction.
  • Change in volume: Density is a characteristic of a compound, and if new compounds are produced as the compounds are consumed in the reaction, the change in density can cause the reacting mixture to expand or contract as the reaction proceeds.
  • Change in melting point or boiling point: The melting or boiling point is characteristic of a compound; when the composition of a mixture changes, the melting point and boiling point also change.
  • Color change: Each and every compound absorbs a distinctive set of colors of light. This absorption spectrum is a chemical fingerprint for detecting the presence of that compound. When the compound is altered in a chemical reaction, the fingerprints will change- and so the color of the reacting mixture may change, as the reaction steps forward.
  • Appearance of bubbles of gas: Only when the gas leaves the reaction mixture, gas-producing reactions will be completed. Bubbles can also be produced when the liquid boils, or when air dissolved in the liquid comes out of solution as the liquid is warmed.
  • Formation of precipitation: When mixing a pair of soluble reactants in solution, the sudden appearance of a solid that precipitates into the bottom of the container is a sign that a reaction has happened.

What are some examples of chemical changes?

  • Oxidation: It is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. There is a chemical change during oxidation seen by rusting or tarnishing.
  • Photosynthesis: It is a process that converts carbon dioxide into organic compounds, in particular sugars, using the energy from sunlight.
  • A most important example of chemical change can be found in the combustion of methane, which produces carbon dioxide and water.
  • Decomposition: Decomposition is the process by which organic material is broken down into simpler forms of matter.
  • Cooking: During cooking, one can observe a lot of chemical changes taking place.
  • Ripening process: A chemical change can be seen in ripening of tomatoes or bananas or any fruit.
  • Neutralization: It is a chemical reaction in which an acid and a base interact with the formation of a salt to make a solution neutral.
  • Cracking of strong hydrocarbons to make lighter hydrocarbons which are a part of the oil refining method. 
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