Pawar Public School, Bhandup
Class:IX
Chemistry Worksheet
Topic: Physical and Chemical Changes
Question:1
(a) Give an example of each of the following energy changes exhibited in a chemical change.
(i)
An exothermic and an endothermic reaction involving nitrogen as one of the reactants.
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(ii)
An exothermic and an endothermic reaction involving carbon as one of the reactants.
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(iii)
A photochemical reaction involving hydrogen as one of the products.
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(iv)
An electrochemical reaction involving water as the reactant.
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(v)
A photochemical reaction involving a silver salt.
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(b) State which of the following are oxidised or reduced and complete the equations by adding or
removing the electrons .
(i) S2-→ S_________________________________________________________________________
(ii) Cl-→ Cl _______________________________________________________________________
(iii) Mn5+→ Mn 7+___________________________________________________________________
(iv) Cl2 → Cl- ______________________________________________________________________
(v) Cr7+→ Cr5+______________________________________________________________________
(c) Name the reducing agent in the following reactions ,the element reduced and also state the change in
the oxidation state .
(i) Fe2O3 + 3CO → 2Fe + 3CO2________________________________________________________
(ii) CuO + H2→ Cu + H2O ___________________________________________________________
(iii) ZnO + C → Zn + CO ____________________________________________________________
(iv) 3CuO + 2NH3→ 3Cu + N2 + 3H2O_________________________________________________
(c) Fill in the blanks:
(i) Heating of camphor is a ______________ change whereas the burning of camphor is a _____________
(ii) A reversible thermal decomposition reaction is called thermal ____________ reaction.
(iii) Reducing agents are electron ____________________________.
(iv) Oxidizing agents are electron ____________________________.
(v) ______________ is the process of loss of electrons.
Question 2:
(a) Match the following:
A
B
(i) Interchange of radicals
(a) Direct combination
(ii) Combination of only elements
(b) Neutralization
(iii) Combination of elements and compounds
(c) Double decomposition
(iv) Reaction for the formation of soluble salts
(d) Precipitation
(v) Reaction for the formation of insoluble salts
(e) Synthesis
(b) Complete the following equations and balance them.
(i) Cu(NO3)2 +
(ii)
(iii)
(iv)
(v)
KBr +
Fe +
NaOH →
Cl 2
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→________________________________
HCl → _________________________
Cu(OH)2 → ______________________________
NO +
O2 → ______________________________
(c) Define the following:
(i) Direct combination reaction :___________________________________________________
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(ii) Decomposition reaction : ______________________________________________________
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(iii) Displacement reaction: ________________________________________________________
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(iv) Double decomposition reaction: __________________________________________________
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(v) Photochemical reaction: ________________________________________________________
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(c) State three conditions for burning. Compare respiration and burning.
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