Changes Around Us: Physical and Chemical - Weathering of rocks

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Weathering is the process of breaking down of rocks into smaller particles by the action of wind, water, and climate. It is a fundamental process in soil formation.

•

Physical Weathering involves the mechanical breaking of rocks into smaller fragments without changing their chemical composition. Examples include frost action and thermal expansion.

•

9\%

•

Chemical Weathering occurs when the minerals in rocks undergo chemical changes to form new substances. This usually involves reactions with water, oxygen, or carbon dioxide.

•

2Fe_{2}O_{3} \cdot nH_{2}O

•

CO_{2}

•

Biological Weathering is the breakdown of rocks by living organisms, such as plant roots growing into cracks or acidic secretions from lichens and mosses.

📐Formulae

4Fe + 3O_{2} \rightarrow 2Fe_{2}O_{3}

H_{2}O + CO_{2} \rightarrow H_{2}CO_{3}

CaCO_{3} + H_{2}CO_{3} \rightarrow Ca(HCO_{3})_{2}

💡Examples

Problem 1:

100 \text{ cm}^3

Solution:

100 + \left( \frac{9}{100} \times 100 \right) = 109 \text{ cm}^3

Explanation:

100 \text{ cm}^3

Problem 2:

CO_{2}

Solution:

Chemical Change (Chemical Weathering)

Explanation:

CaCO_{3}

Problem 3:

112 \text{ g}

Solution:

\begin{array}{r} 112 \\ + 48 \\ \hline 160 \end{array}

Explanation:

160 \text{ g}