Mechanical and Chemical Weathering - Answers

Mechanical and Chemical Weathering Name: ___________________Nigel Cooper_________________________________________ Period: _________ Date: ___2023_____ Essential Question: How is weathering affected by climate, surface area, rock composition, and pollution? Weathering - the disintegration and decomposition of rock at or near the surface of the earth or simply the breaking of rocks. It affects the rocks in place and no transport is involved. This distinguishes weathering from erosion. Two Types of Weathering 1. Mechanical/physical weathering - physical disintegration of a rock into smaller fragments, each with the same properties as the original. Occurs mainly by temperature and pressure changes. 2. Chemical weathering - process by which the internal structure of a mineral is altered by the addition or removal of elements. Change in phase (mineral type) and composition are due to the action of chemical agents. Chemical weathering is dependent on available surface for reaction temperature and presence of chemically active fluids. Erosion - the incorporation and transportation of weathering products by a mobile agent such as wind, water, ice. Simply, erosion happens when sediments are moved by water, ice, wind, living things and other agents. Factors that affect the rate of weathering 1. CLIMATE: The amount of water in the air and the temperature of an area are both part of an area’s climate. Moisture speeds up chemical weathering. Weathering occurs fastest in hot, wet climates. It occurs very slowly in hot and dry climates. Without temperature changes, ice wedging cannot occur. In very cold, dry areas, there is little weathering. 2. SURFACE AREAMost weathering occurs on exposed surfaces of rocks and minerals. The more surface area a rock has, the more quickly it will weather. When a block is cut into smaller pieces, it has more surface area. So, therefore, the smaller pieces of a rock will weather faster than a large block of rock 3. ROCK COMPOSITIONSome minerals resist weathering. Quartz is a mineral that weathers slowly. Rocks made up of minerals such as feldspar, calcite, and iron, weather more quickly. 4. Pollution speeds up weathering. Factories and cars release carbon dioxide and other gases into the air. These gases dissolve in the rainwater, causing acid rain to form. Acid rain contains nitric and sulfuric acid, causing rocks and minerals to dissolve faster. CHEMICAL REACTIONS When Carbon Dioxide dissolves in rainwater, carbonic acid is produced. As the rainwater moves through soil, the carbonic acid dissolves calcite (a mineral found in marble and limestone). Limestone caves, underground caves, cavern, or Karst topography are a result of this kind of weathering. Karst topography usually forms sinkholes. Clarifying Questions: 1. What is weathering? Weathering is the process of breaking down rocks, soil, and minerals through exposure to the atmosphere, water, and biological activity. _________________________________________________________________________________________ 2. How is weathering different from erosion? Think! Weathering breaks down rocks into smaller pieces, while erosion involves the movement and transport of these _________________________________________________________________________________________ weathered materials. _________________________________________________________________________________________ 3. What are the two types of weathering? The two types of weathering are mechanical weathering and chemical weathering. _________________________________________________________________________________________ 4. What is mechanical weathering? Mechanical weathering physically breaks down rocks into smaller fragments without changing their chemical composition. _________________________________________________________________________________________ 5. What is chemical weathering? _________________________________________________________________________________________ Chemical weathering involves the alteration of rock minerals through chemical reactions, leading to their decomposition and dissolution. For items 6-10: Mechanical or Chemical weathering. Write the letter of your answer on the blank. A. Mechanical weathering B. Chemical weathering _A_6. Occurs mainly by temperature and pressure changes. Like frost wedging. _B_7. Rocks break with their minerals altered by the addition or removal of elements __A__ 8. Rocks break into smaller fragments, each with the same properties as the original. __B__9. Type of weathering dependent on surface for reaction and presence of chemically fluids like acids. _A__10. Also known as physical weathering. 11. What is erosion? Erosion is the process of transporting weathered materials, like rock fragments and soil particles, by natural agents such as water, wind, ice, or gravity. _________________________________________________________________________________________________________________________________ 12. How can increasing the surface area of rock hasten or speed up the process of weathering Think! 10 pts.? Increasing the surface area of rock speeds up weathering because it exposes more rock to weathering agents, such as water ________________________________________________________________________________________________ and air, facilitating chemical reactions and mechanical processes ________________________________________________________________________________________________ Factors that affect the rate of weathering Completion: Write the missing word or words on the space before each number. For items 13-20 _H_13. ___speeds up chemical weathering. _A_14. Weathering is _____________ in hot, wet (humid) climates. _B_15. Weathering occurs very slowly in _______ and ______ climates. _G_16. Without ________ , ice wedging cannot occur _C_17. In very ________ and ________ areas, there is little weathering. _D_18. Most weathering occur on ______of rocks and minerals _E__19. The ____surface area a rock has, the ___ it will weather. _F_20. Some minerals resist weathering. ___________ is a mineral that weathers slowly. Rocks made up of minerals such as feldspar, ______, and iron, weather more quickly. A. B. C. D. E. F. G. fastest hot, dry cold, dry exposed surfaces higher, faster quartz, calcite temperature changes H. moisture 21. How can pollution hasten or speed up weathering? It can speed up weathering by introducing acidic substances, like sulfur dioxide and nitrogen oxides, which react with water vapor to _________________________________________________________________________________________________________________________________ form acid rain. This acid rain accelerates the chemical weathering of rocks. 22. What is karst topography and what does it form? Karst topography is a landscape shaped by the dissolution of soluble rocks, like limestone, gypsum, and dolomite, by slightly acidic ________________________________________________________________________________________________ groundwater. It forms features such as sinkholes, caves, and underground drainage systems. ________________________________________________________________________________________________ __B__23. Cracks in rocks widen as water in them freezes and thaws. How does this affect the surface of Earth? A. It reduces the rates of soil formation. B. It exposes rocks to increased rates of erosion and weathering. 23. Matching type: Climate and Weathering ___A______ hot, wet climates. A. weathering is fastest ___B_____ hot and dry climates. B. very slow weathering ___D_____ cold, dry areas C. Frost wedging does not happen ___C_____ no temperature D. little weathering changes 25. Name the four factors that can hasten or speed up the process of weathering. Climate, Type of rock, Surface area, Presence of vegetation or organisms _____________________________________________________________________________________