Weathering: physical, chemical, and biological

Correct answer: B. Because evaporation can form salt crystals

In dry regions, evaporation can leave salts as crystals. Remember salt and dryness together in exams.

Correct answer: C. Chemical nature of minerals may change

Chemical weathering may change the chemical nature of minerals. Identify mineral change in exams.

Correct answer: D. Cracks and breaking in rock

Heating and cooling make rocks expand and contract, causing cracks. In exams, understand it as physical weathering.

Correct answer: A. Biological weathering

In biological weathering, plants, organisms, and humans affect rocks. Identify living agents in exams.

Correct answer: B. Chemical weathering

Limestone dissolves and changes chemically. In exams, link dissolution and limestone with chemical weathering.

Correct answer: A. Breaking of rocks into small particles

Weathering can break rocks into small particles. Remember rock breaking as a simple result in exams.

Correct answer: B. They release acidic substances and weaken the surface

Lichens can release acidic substances and weaken rock surfaces. In exams, take lichens as an example of biological weathering.

Correct answer: C. Climate

Climate controls weathering rate through temperature and moisture. In exams, consider climate a major control.

Correct answer: D. It generally remains the same

In physical weathering, rock breaks but chemical composition generally remains the same. Remember only size change in exams.

Correct answer: A. It helps many reactions and solution

Water helps dissolve minerals and cause chemical reactions. In exams, treat water as the main medium of chemical weathering.

Correct answer: A. Cracks may become wider

Plant roots can enter small cracks in a rock and become thicker as the plant grows. Their growth presses against the sides of the crack, gradually forcing the opening wider. Repeated wetting, drying, and root growth can weaken the rock further. This is a form of biological weathering because a living organism contributes to the physical breakdown of the rock without melting it or turning it into a gas.

Option A is correct because roots may widen existing cracks. The wording “may become wider” is important: the change is gradual, not immediate, and its size depends on the rock, the root, and environmental conditions. A rock does not melt simply because a root enters it, nor does it become smoke. Weather does not stop; instead, biological activity works together with other weathering processes to weaken the material.

Correct answer: B. Expansion and contraction by heat

Expansion and contraction by heat is physical weathering. In exams, treat reaction-based examples as chemical.

Correct answer: A. Tree roots

Correct answer: A, tree roots. Biological weathering is the breakdown or alteration of rock caused by living organisms such as plants, animals, and microorganisms. Tree roots may enter tiny cracks and enlarge them as the roots grow. This can physically split or loosen the rock without transporting it away. A is therefore the only option that names a living biological agent. B, salt crystals, can grow in pores and cracks and exert pressure, but that is generally treated as a physical weathering process. C, temperature difference, causes expansion and contraction and is also a physical process. D, ice pressure is related to freeze-thaw action, in which water freezes, expands, and widens cracks; it is physical weathering, not biological weathering. Memory cue: ask “Is a living organism doing the work?” If yes, think biological weathering.

Correct answer: B. Lithosphere

Weathering is the breakdown or alteration of rock at or near Earth’s surface. It affects the solid rocky material that forms the lithosphere, including exposed rocks, soil-forming material, and the upper part of the crust. Physical weathering breaks rock into smaller pieces, chemical weathering changes or dissolves minerals, and biological weathering involves organisms such as roots or burrowing animals.

Option B, the lithosphere, is therefore the best answer. The atmosphere is the layer of gases around Earth, and the stratosphere is only one part of that atmosphere. The ionosphere is a region of the upper atmosphere affected by charged particles, not the main solid surface where rocks weather. Weathering can interact with air and water, but the material being weathered is chiefly part of the lithosphere.

Correct answer: C. Reddish-brown colour

The direct answer is C, reddish-brown colour. Oxidation is a chemical reaction in which a mineral reacts with oxygen. Iron-bearing minerals can form iron oxides, similar to rust on iron objects. Step by step: oxygen and moisture reach iron-containing minerals; the iron reacts and produces oxide minerals; these commonly give the rock a red, brown, or yellowish-brown appearance; the reaction may also weaken the rock. Option C is correct because a rust-like reddish-brown colour is a common visible sign of oxidation in iron-rich rocks. Option A is wrong because blue transparency is not the usual result of iron oxidation. Option B is wrong because oxidation is a chemical alteration, not chemical inactivity. Option D is wrong because iron-bearing rocks do not normally evaporate completely through oxidation. Some rocks may show different shades depending on minerals and moisture, so ‘may appear’ is appropriately cautious. Memory cue: iron plus oxygen often means rust-coloured weathering.

Correct answer: D. All can weaken or change rocks

All three types can weaken, break, or change rocks. In exams, their methods differ but their effect is on rocks.

Correct answer: A. Cold and dry condition

Chemical reactions are slow in cold and dry conditions. In exams, link heat and moisture with faster chemical weathering.

Correct answer: B. Because it changes surface material

Weathering changes rocks and surface materials, helping landform development. In exams, understand geomorphic as surface change.

Correct answer: C. Hydration

In hydration, water joins minerals and their volume may increase. Identify hydration by water absorption in exams.

Correct answer: B. Physical weathering

In physical weathering, pieces may separate but mineral composition does not change. Remember breaking and no chemical change in exams.

Correct answer: C. Biological weathering

Roots, lichens, and bacteria are linked with living agents. In exams, write them as examples of biological weathering.

Correct answer: B. Helping minerals react with oxygen and moisture

Oxygen and moisture in air can increase chemical weathering. Exam tip: connect air with oxidation.

Correct answer: A. Because they remain in direct contact with water, air, and temperature

Exposed parts are in direct contact with water, air, and temperature, so weathering can be faster. In exams, treat exposed surface as an important factor.

Correct answer: B. Moisture helps chemical reactions and dissolution

Moisture helps minerals dissolve and react. In exams, connect moisture with the rate of chemical weathering.

Correct answer: C. Root growing in a crack and breaking rock

A root is a living agent and can apply pressure in cracks causing mechanical breaking. In exams, treat it as a clear example of biological weathering.