Chemical Reaction

Chemical Reaction

Chemical Reactions

Chemical Reaction is an important and fundamental concept in Chemistry. It is also an integral part of our body and we might have experienced it in our day to day life. In this session, we will discuss and understand more about:

1. What is chemical reaction
2. Different signs that represent chemical reaction

What is chemical reaction?

Chemical reaction is a process, by which one or more substances undergo a chemical change to produce one or more different substances. It means, whenever any process occurred in which one or more substances (which are considered as reactants) take part and they allowed to produce one or more different substances (called as products). Such kind of process is considered as chemical reaction.

In simple representation of chemical reaction, you can see that the reactant part mentioned at left hand side and the product part always mentioned at the right hand side. Arrow shows in which direction the chemical process is going.

Reactants → Products

Reactants allowed to take apart in reaction, to change in their position of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei. This reaction allowed to form new bonds & form new products which have complete different chemical representation, properties & identity.

Let’s go through some examples of chemical reaction which occur in our everyday life.

  • Making of Curd (Curdling)
    • Lactose + Water → Lactic Acid
    • C12H22O11 + H2O → 4C3H6O3
  • Photosynthesis in Plants
    • Carbon Dioxide + Water + Solar Energy → Glucose + Oxygen
    • 6CO2 + 6H2O + Solar Energy → C6H12O6 + 6O2
  • Burning of Wood
    • Wood + Oxygen → Carbon Dioxide + Water Vapour + Ash + Heat
  • Food Digestion
    • Digestion of Glucose
      • C6H12O6 + 6O2 → 6H2O + 6CO2
    • Digestion of Proteins
      • Protein + Pepsin → Amino acids
    • Digestion of Fats
      • Fat droplets + Water + Lipase → Glycerol + Fatty acids
  • Rusting of Iron
    • Iron + Oxygen + Water → Iron Rust
    • 4Fe + 3O2 + 6H2O → 4Fe(OH)3

Signs of chemical reaction


There are some kind of signs indications which help us to understand how the chemical reaction is moving or if chemical reaction is in process or not.

So the general five signs which help us to indicate the chemical reaction has taken place.
Signs of Chemical Reactions
Signs of Chemical Reactions
1. Production of Gas
    • Burning of fuel, whenever the fuel get burn it will release carbon dioxide.
    • Coal or wood or any kind of the other fossil fuel, If it is good to burn so it will release gas in the form of carbon dioxide and other gases
So, production of gas is an indication, which helps us to understand that chemical reaction has taken place.

2. Change in Color of Substance
    • Whenever the reactant take a part in reaction and it get converted into product, we can see colour of reactant and the product, can be different from each other.
    • Ex. Rusting of Iron – When iron get rusted, it’s colour changes from grayish black to reddish brown because the iron get oxidize and get converted into rust.
So, change in color is an indication of chemical reaction has taken place

3. Change in Temperature
    • It’s most commonly occurred in the burning process like in combustion reaction, burning of fuel, burning of light stick
    • Ex. Burning of Magnesium Ribbon – gets converted into ash
So, change in temperature (of product as compared to the reactant part) is an indication of chemical reaction

4. Formation of Precipitate
    • Precipitate is nothing but the un-dissolved solid part which is formed as the product of the reaction.
    • Ex. Clogging of pipe because solid precipitates are present in the water
Some salts like magnesium chloride and calcium chloride, forms white precipitate & gets settled down at the bottom of the vessel when the water is allowed to flow

5. Change in State (Solid, Liquid, Gas)
    • Three most common physical states – Solid, Liquid & Gas
    • Ex. Burning of Candle – It get change in its state from the solid to liquid, then it gets converted from liquid to gas

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