Question
Explain giving two examples of chemical change.
✓
Answer
(1) When carbon is burnt, carbon dioxide is formed. In this process carbon combines with oxygen, therefore carbon and oxygen are reactants, while curbon dioxide is a product. This change is permanent.
$C _{( s )}+ O _{2( g )} \stackrel{\text { Heat }}{\longrightarrow} CO _{2( g )}$
(2) When a magnesium wire is burnt in air, a white powder of magnesium oxide is formed. We cannot obtain magnesium from magnesium oxide by simple methods. Properties of magnesium oxide are altogether different from those of magnesium. A new substance MgO is formed in the reaction. Hence, this change is a chemical change.
$\underset{\text { Magnesium }}{2 Mg }+ O _2 \stackrel{\Delta}{\longrightarrow} \begin{gathered}2 MgO \\ \text { Magnesium oxide }\end{gathered}$
$C _{( s )}+ O _{2( g )} \stackrel{\text { Heat }}{\longrightarrow} CO _{2( g )}$
(2) When a magnesium wire is burnt in air, a white powder of magnesium oxide is formed. We cannot obtain magnesium from magnesium oxide by simple methods. Properties of magnesium oxide are altogether different from those of magnesium. A new substance MgO is formed in the reaction. Hence, this change is a chemical change.
$\underset{\text { Magnesium }}{2 Mg }+ O _2 \stackrel{\Delta}{\longrightarrow} \begin{gathered}2 MgO \\ \text { Magnesium oxide }\end{gathered}$
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