Chemistry
Which of the of following is not a chemical change.
- Rusting of iron
- Iron is magnetised
- Potassium is dissolved in water
- Magnesium wire is burnt
Chemical Reaction
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Answer
Iron is magnetised
Reason — Magnetisation of iron is not a chemical change, as it is a temporary change. Magnetising iron only changes its magnetic properties, no new substance is formed.
The others are chemical change because:
- Iron reacts with oxygen and moisture to form a new substance iron oxide.
- Potassium reacts vigorously with water to form Potassium hydroxide and hydrogen gas. A new substance forms, so it's chemical.
- Magnesium reacts with oxygen to form Magnesium oxide, a new substance, along with bright light and heat.
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Related Questions
(a) What are double displacement reactions?
(b) Give an example of a double displacement reaction, where gas is evolved.
State the type of reactions each of the following represent and balance the ones that are not balanced.
(a) Cl2 + 2KBr ⟶ 2KCl + Br2
(b) NaOH + HCl ⟶ NaCl + H2O
(c) 2HgO ⟶ 2Hg + O2 ↑
(d) Fe + CuSO4 ⟶ FeSO4 + Cu
(e) PbO2 + SO2 ⟶ PbSO4
(f) 2KClO3 ⟶ 2KCl + 3O2 ↑
(g) 2H2O2 ⟶ 2H2O + O2 ↑
(h) KNO3 + H2SO4 ⟶ HNO3 + KHSO4
(i) CuO + H2 ⟶ Cu + H2O
(j) CaCO3 ⟶ CaO + CO2 ↑
(k) NH4Cl ⟶ NH3 + HCl
(l) PbO + 2HNO3 ⟶ Pb(NO3)2 + 2H2O
(m) AgNO3 + NaCl ⟶ AgCl ↓ + NaNO3
Heating of zinc nitrate is a …………… reaction.
- Displacement
- Combination
- Decomposition
- Redox
Burning of a metal is an example of :
- Decomposition reaction
- Combination reaction between an element and a compound
- Direct combination reaction between two elements
- Displacement reaction