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CBSE NOTES ⇒ Class 10th ⇒ Science ⇒ 1. Chemical Reactions and Equations

1. Chemical Reactions and Equations

Chemical Reaction


The theoretical and experimental study of nature, composition, preparation, isolation, properties and uses of matter is known as Chemistry.

Chemical Reaction:  Such a process in which there produces substances of new property is known as chemical reaction.  Ex.

2H2 + O2 → 2H2O

(Here H2 and O2 take part in chemical reaction and produce a product of new property i.e. H2O.)

In other hand, we can also say that Chemical changes are also known as chemical reaction. There are many chemical changes which occur around us.


  • Iron rod comes in contact of moisture and gets rusted.
  • Grapes get fermented.
  • Food is cooked.
  • Food gets digested in our body.
  • We respire.

Determination of Chemical Reaction:

We should have a criteria to determine the chemical reaction has taken place.


  • change in state
  • change in colour
  • evolution of a gas
  • Change in temperature.


Above four points are identifications of chemical reaction which indicate that the reaction has taken place.


Chemical Equation

when a magnesium ribbon is burnt in oxygen, it gets converted to magnesium oxide. This is the statement form of a chemical reaction but it can be write as a following manners

Magnesium + Oxygen → magnesium oxide

        (Reactants)                      (product)

To write the equation in such manner is called as word equation.

Another method to write chemical reaction;

Mg + O2 → MgO

This is symbolic form to write chemical equations. 

There are two part of a chemical reaction

  1. Reactants: The substances that undergo chemical change in the reaction  are the reactants. Example from above equation. Mg and O are reactants.
  2. Procducts: The new substance,  formed during the reaction, is the product. Ex. MgO is product, which newer substance produced in reaction. 

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Study Materials List:

CBSE NOTES ⇒ Class 10th ⇒ Science
1. Chemical Reactions and Equations
2. Acids, Bases and Salts
3. Metals and Non-metals
4. Carbon and its Compounds
5. Periodic Classification of Elements
6. Life Processes
7. Control and Coordination
8. How do Organisms Reproduce
9. Heredity and Evolution
10. Light-Reflection and Refraction
11. Human Eye and Colourful World
12. Electricity
13. Magnetic Effects of Electric Current
14. Sources of Energy
15. Our Environment
16. Management of Natural Resources

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