cbse notes for class 10 science|Cbse notes of class 10 chemistry to score 95 +
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Notes of ch 1 class 10 chemistry
Chemical reaction and equation
Chemical reaction
The method of representing a chemical reaction with the help of symbol and formula of the substance involved in it is known as chemical reaction.
Whenever and chemical reaction takes place following things happen
→Change in colour
→change in state
→change in temperature
→evolution of gas
Balanced chemical equation
Equation in which the number of atoms are equal in both side reactant side as well as product side.
Reactant side - LHS of equation is called reactant side.
Product side - RHS of equation is called product side.
Why balancing is necessary?
According to law of conservation of mass can neither be created not destroy in chemical reaction. That is, the total mass of the elements present in the product and reactant of chemical reaction has to be equal.
Example Zn + H2SO4 →ZnSO4 + H2
The method of balancing the equation is called hit and trial.
°Type of chemical reaction
→ combination reaction
→ decomposition reaction
→ double displacement reaction
→ displacement reaction
→ Redox reaction
Combination reaction - reaction in which two or substance( element or compound) combined to form a single product.
2H2+O2→2H2O
››Hydrogen + oxygen → water
››Carbon + Oxygen → carbon dioxide
Ca + O2 →CO2
Decomposition reaction - reaction in which one substance break into two or more substance is known as decomposition reaction.
Types of decomposition reaction
→Thermal decomposition reaction
→ photo light decomposition reaction
→ electric decomposition
Thermal decomposition reaction
Decomposition reaction in which heat is required to break down of substance is known as thermal decomposition reaction
2FeSO4→Fe2O3 + SO2 + SO3
Ferrous sulphate →ferricoxide + sulphur dioxide + sulphur trioxide
CaCO3 → CaO + CO2
Photolytic decomposition reaction
Decomposition reaction take place by light is known as photolytic decomposition reaction.
2AgCl→2Ag + Cl2
2AgBr→2Ag + Br
Electric decomposition
Decomposition reaction take place by electricity is known as Electric decomposition .
2H2O →2H2 + O2
Displacement reaction
Reaction in which high reactive element displaces less reactive element from its solution.
Zn+ CuSO4 →ZnSO4 + Cu
Double displacement reaction
Reaction in which exchange of Ion take place is known as double displacement reaction.
Pb(NO3) 2 +KI →PbI2 + kNO3
BaCl2+ Na2SO4 →BaSO4 + 2NaCl
»precipitation reaction
Reaction in which an insoluble solid is formed is known as precipitation reaction.
BaCl2+Na2SO4→2Nacl + BaSO4
Here BaSO4 is insoluble solid or ppt
Redox reaction
Reaction in which oxidation and reduction both take place is known as Redox reaction.
2Cu+O2→2CuO
★ oxidation- addition of Oxygen and removal of hydrogen is known as oxidation
★ reduction - removal of Oxygen and addition of hydrogen is known as reduction.
Example CuO + H2 →Cu + H2O
ZnO+ C → Zn + CO
→corrosion - when the surface of metal is get eaten by its surrounding substance such as moisture, acids etc and form a undesirable substance is called corrosion.
Example Rusting of iron.
→ rancidity - when substance containing fat and oil are oxidised they become rancid and their smell and taste get changed this process is known as rancidity
Method to prevent rancidity
Use antioxidants.
Use air tight container.
Use nitrogen to flush it.
Use refrigerator.