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Observation and conclusion: When we blow air (carbon dioxide) from mouth to tumbler A containing water, we do not observe any change in the colour of water. But when we blow air into tumbler B containing lime water (calcium hydroxide), lime water turns milky and white-coloured insoluble substance (calcium carbonate) gets settle down. Thus, this is classified as chemical change as new substance is being formed.
$\begin{array}{l}\text { Carbon dioxide }\end{array}+\underset{\text { (calcium hydroxide) }}{\text { Lime water }} \rightarrow \underset{\text { carbonate (milky) }}{\text { Calcium }}+ \text { water }$
$\begin{array}{l}\text { Carbon dioxide }\end{array}+\underset{\text { (calcium hydroxide) }}{\text { Lime water }} \rightarrow \underset{\text { carbonate (milky) }}{\text { Calcium }}+ \text { water }$
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