Weathering: physical, chemical, and biological

Correct answer: A. Crystals exert pressure on crack walls

Salt crystallisation increases pressure in pores and cracks. Exam tip: link this process with arid areas and coasts.

Correct answer: B. Warm and humid climate

Water and heat help chemical reactions. Exam tip: connect warm humid regions with chemical weathering.

Correct answer: C. Carbon dioxide rich water

Carbon dioxide mixes with water to form a weak acid. Exam tip: link limestone with carbonation.

Correct answer: D. They may form rust-like reddish brown compounds

Iron reacts with oxygen and moisture to form rust-like compounds. Exam tip: treat reddish brown colour as a sign of oxidation.

Correct answer: A. Water participates in changing mineral composition

In hydrolysis water chemically reacts with minerals. Exam tip: remember feldspar changing into clay minerals.

Correct answer: B. Rock salt

The direct answer is B, rock salt. Solution weathering occurs when water dissolves soluble minerals and carries the dissolved material away. Rock salt is made mainly of halite, a mineral that dissolves readily in water, so water can remove it relatively easily. Step by step: water reaches the mineral; the soluble mineral goes into solution; flowing water transports the dissolved substance; the rock gradually loses material. Option A, granite, contains several minerals, including quartz and feldspar, but it is not as readily dissolved as rock salt. Option B is correct because salt is highly soluble and therefore a clear example of solution weathering. Option C, basalt, is a volcanic rock that can undergo chemical weathering, but it is not the best example of easy dissolution among these choices. Option D, quartzite, is rich in quartz, which is relatively resistant to weathering and does not dissolve readily in ordinary water. Gypsum can also show solution weathering, but it is not listed. Memory cue: soluble minerals such as salt are removed by solution.

Correct answer: C. They grow in cracks and widen them

Growing roots can exert pressure in cracks. Exam tip: connect tree roots with both biological and physical effects.

Correct answer: D. They loosen and mix soil and rock material

Organism activity breaks and moves material. Exam tip: treat animal burrowing as an example of biological weathering.

Correct answer: A. It forms new clay minerals and dissolved materials

Chemical changes can turn minerals into soil components. Exam tip: consider weathering as an initial process of soil formation.

Correct answer: A. Corners have greater exposed surface effect and reaction

Corners and edges are more exposed so they change faster. Exam tip: remember the formation of rounded shapes from blocky rock.

Correct answer: B. Frost action and freezing of water

Frost action is linked with freezing and expansion of water. Exam tip: match process and example correctly.

Correct answer: C. By making smaller pieces and increasing surface area

Smaller particles provide more surface for chemical reaction. Exam tip: connect surface area with rate of weathering.

Correct answer: D. Because diurnal temperature range can be high

High temperature range causes repeated expansion and contraction. Exam tip: remember the link between deserts and temperature range.

Correct answer: A. Carbonation and solution action

Carbon dioxide rich water can slowly dissolve limestone. Exam tip: connect karst landforms with carbonation.

Correct answer: B. They allow more water and air entry and speed up weathering

Cracks provide pathways for weathering agents to enter. Exam tip: jointed rocks are considered more vulnerable.

Correct answer: C. The surface remains directly exposed to heat and rain

Vegetation acts as a protective cover over the ground. Leaves and branches reduce the direct impact of raindrops, while roots hold soil and partly shield cracks in rocks. On a vegetation-free slope, the rock and soil surface are directly exposed to sunlight, heating, cooling, and rainfall. Repeated heating and cooling can cause expansion and contraction, and rainwater can enter cracks and weaken the material. These conditions can make physical breakdown more visible.

Choice C is correct because the surface remains directly exposed to heat and rain. Choice A is wrong because a bare slope can receive sunlight; choice B describes chemical dissolution and is too absolute; and choice D is wrong because gravity still acts on every slope. Vegetation does not stop all weathering, but its absence removes an important protective layer. The question asks why physical weathering may be stronger, not why erosion is always greater.

Correct answer: A. They may absorb water and expand

Some minerals absorb water and swell which can weaken rock. Exam tip: remember hydration as taking up water.

Correct answer: C. It helps in both solution and chemical reactions

Water can be both a medium and reactant in many chemical processes. Exam tip: treat water as a major agent of weathering.

Correct answer: D. Some minerals weather faster than others

Minerals differ in stability so weathering rates vary. Exam tip: connect mineral composition with resistance to weathering.

Correct answer: A. Organisms can produce organic acids and cause chemical changes

Biological activity may include root pressure and acids. Exam tip: remember the dual effect of biological weathering.

Correct answer: B. Temperature can fluctuate around freezing point there

Frost action is effective when freezing and thawing repeat. Exam tip: link altitude with freeze-thaw cycles.

Correct answer: C. High evaporation with dissolved salts available

Evaporation can form salt crystals and create pressure. Exam tip: link dry coastal areas with salt weathering.

Correct answer: D. Weathering helps change rocks into parent material

Parent material becomes the basis of soil formation. Exam tip: treat weathering as an initial link in soil development.

Correct answer: A. Any rock where weathering agents can enter inside

Cracks allow water air and roots to penetrate. Exam tip: connect structural weakness with weathering rate.

Correct answer: B. Breakdown dominates in physical and mineral change dominates in chemical

Physical weathering mainly means mechanical breakup and chemical weathering means mineral alteration. Exam tip: identify the language of breakup and alteration.