We have studied the difference between physical and chemical changes. In this lesson we would study how we can define the occurrence of a chemical reaction. There are few ways through which we can detect a chemical reaction.
Color Change
Production of an Odor
Change in Temperature
Formation of Bubbles
Precipitate
Explanation:
Color Change: think about the chemical reaction between iron and oxygen. This reaction is called 'rusting'. In this reaction the color of the iron changed from silver-grey to orange-brown.
Iron + Oxygen----- iron oxide
Production of odor: the reaction between amino acid and glucose produces variety of smells, making it easy to detect the occurrence of chemical reactions.
Change in Temperature: consider the reaction between hydrochloric acid and sodium hydroxide, when the reaction takes place, a lot of heat is released and the temperature increases.
Hydrochloric acid + sodium hydroxide ------- sodium chloride + water
Formation of Bubbles: in most of the reaction, gases are released. When these gases are released bubbles are seen. Through the formation of bubbles, we can detect that chemical reaction has taken place. But keep in mind, that boiling is not a chemical reaction, even if bubbles form.
Sulfuric acid + aluminum --------- aluminum sulfate + hydrogen (gas)
Precipitate: in the reaction between silver nitrate and sodium chloride, a white, silver chloride precipitate is formed. Silver chloride solid moves down in the beaker and settle down forming a precipitate.
Silver nitrate + sodium chloride ------- silver chloride + sodium nitrate
*pictures taken form google*
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