Q. Consider the following statements:

Statement I:
In the context of effect of water on rocks, chalk is known as a very permeable rock whereas clay is known as quite an impermeable or least permeable rock.

Statement II:
Chalk is porous and hence can absorb water.

Statement III:
Clay is not at all porous.

Which one of the following is correct in respect of the above statements?
(a) Both Statement II and Statement III are correct and both of them explain Statement I
(b) Both Statement II and Statement III are correct but only one of them explains Statement I
(c) Only one of the Statements II and III is correct and that explains Statement I
(d) Neither Statement II nor Statement III is correct

48. निम्नलिखित कथनों पर विचार कीजिए:
कथन I :
शैलों पर जल के प्रभाव के संदर्भ में, चॉक एक अत्यंत पारगम्य शैल के रूप में ज्ञात है, जबकि मृत्तिका एक नितांत अपारगम्य या न्यूनतम पारगम्य शैल के रूप में ज्ञात है।

कथन II :
चॉक सरंध्र होता है, अतः जल अवशोषित कर सकता है।

कथन III:
मृत्तिका बिल्कुल ही सरंध्र नहीं है।

उपर्युक्त कथनों के संदर्भ में, निम्नलिखित में से कौन-सा एक सही है?
(a) कथन IIऔर कथन III दोनों सही है तथा वे दोनों कथन I की व्याख्या करते हैं
(b) कथन II और कथन III दोनों सही है किन्तु उनमें से केवल एक, कथन I की व्याख्या करता है
(c) कथन II और कथन III में से केवल एक सही है तथा वह कथन I की व्याख्या करता है
(d) न तो कथन II और न ही कथन III सही है

Answer: C

Explanation:

Porosity and permeability are related properties of any rock or loose sediment. Both are related to the number, size, and connections of openings in the rock. More specifically, porosity of a rock is a measure of its ability to hold a fluid. Permeability is a measure of the ease of flow of a fluid through a porous solid. A rock may be extremely porous, but if the pores are not connected, it will have no permeability.

Statement 1 is correct: Chalk is a porous rock with high permeability, allowing water to flow through it easily. Clay, on the other hand, has very low permeability due to its fine-grained structure, which restricts water flow.

Statement 2 is correct: Chalk is a porous rock, meaning it has spaces (pores) that can hold water. This porosity contributes to its ability to absorb water.

Statement 3 is not correct: Clay is porous, but its pores are very small and interconnected in a way that restricts water flow, making it impermeable. The small pore size and high surface area of clay particles impede the flow of water, even though the material itself is porous.

Source:
https://www.sciencedirect.com/science/article/abs/pii/S0013795221000703

https://deq.louisiana.gov/assets/docs/Water/DWPP_forkidsandeducators/PorosityandPermeability.pdf