8 g rocks & weathering (boardworks)

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Published on March 31, 2014

Author: PreetiGhosh2

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© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20051 of 30 KS3 Chemistry 8G Rocks and Weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20052 of 30 8G Rocks and Weathering Summary activities Physical weathering After weathering Contents Biological weathering Chemical weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20053 of 30 Rocks and weathering Why are rocks all different shapes and sizes?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20054 of 30 Rocks and weathering Rocks are different shapes and sizes because they are changed by the conditions in their environment. The breakdown of rocks into smaller fragments is called weathering. There are three types of weathering:  physical weathering  chemical weathering  biological weathering What factors cause these different types of weathering?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20055 of 30 How can freezing cause damage? What will happen to a glass bottle containing a liquid if it is left in a freezer for too long? The liquid inside the bottle expands as it freezes. The ice formed creates huge forces on the glass which then cause the bottle to break! How does this explain why water pipes often burst in winter? It shatters!It shatters!

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20056 of 30 Freeze-thaw weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20057 of 30 1. Water finds its way into small cracks in the rock. What will happen to the water if the temperature drops to 0 C or below? How does freeze-thaw weathering happen?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20058 of 30 How does freeze-thaw weathering happen? 2. At night-time, when the temperature drops to 0 C or below, the water in the crack freezes forming ice. The water expands as it freezes creating huge forces on the surrounding areas of the rock. These forces make the crack in the rock get bigger.

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20059 of 30 How does freeze-thaw weathering happen? At night-time this water freezes again. 3. During the day, when the temperature warms up again, the frozen water thaws. This cycle of freezing and thawing is repeated over and over again. The huge forces created cause more cracks to appear in the rock.

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200510 of 30 4. Finally a fragment of the rock breaks away completely. This process is called freeze-thaw weathering. Freeze-thaw weathering is a type of physical weathering. How does freeze-thaw weathering happen?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200511 of 30 Exfoliation or onion-skin weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200512 of 30 How does onion-skin weathering happen? 1. During the day the sun heats up the surface of the rock causing the rock to expand. 2. During the night the rock cools down and contracts. 3. As the rock keeps expanding and contracting, pieces of surface rock begin to flake and fall off. Onion-skin weathering is a type of physical weathering.

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200513 of 30 8G Rocks and Weathering Summary activities Physical weathering After weathering Contents Biological weathering Chemical weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200514 of 30 What is biological weathering?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200515 of 30 Examples of biological weathering How has biological weathering caused these cracks to form?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200516 of 30 8G Rocks and Weathering Summary activities Physical weathering After weathering Contents Biological weathering Chemical weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200517 of 30 What is chemical weathering?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200518 of 30 Rainwater is naturally acidic because carbon dioxide in the air reacts with rainwater to form carbonic acid. This type of acid rain is weakly acidic and reacts slowly with minerals in rock. The burning of fossil fuels produces oxides of sulphur and nitrogen which make rainwater more acidic. This type of acid rain reacts quickly with minerals and weather rock more rapidly. Slow chemical weathering Slow and rapid chemical weathering Rapid chemical weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200519 of 30 Examples of chemical weathering How has chemical weathering affected these rocks?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200520 of 30 8G Rocks and Weathering Summary activities Physical weathering After weathering Contents Biological weathering Chemical weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200521 of 30 What happens to weathered rock?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200522 of 30 What is transportation? Transportation is the movement of rock fragments from one place to another. The rock fragments can be transported in different ways: by strong windsby strong winds by riversby rivers by glaciersby glaciers

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200523 of 30 What is deposition? Deposition occurs when pieces of weathered rock sink to the bottom of the river bed or sea forming sediment. Dead creatures can get trapped in sediment and form fossils.

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200524 of 30 How are sedimentary rocks formed?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200525 of 30 Examples of sedimentary rocks How can you tell that these are sedimentary rocks?

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200526 of 30 From weathering to sedimentation

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200527 of 30 8G Rocks and Weathering Summary activities Physical weathering After weathering Contents Biological weathering Chemical weathering

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200528 of 30 Glossary deposition – The settling of rock fragments after transportation. erosion – The process of weathering and transportation. exfoliation – Weathering of rocks caused by repeated heating and cooling, also called onion-skin weathering. freeze-thaw – Weathering of rocks caused by the repeated freezing and thawing of water in cracks in rocks. grain – A small piece of a mineral which makes up a rock. mineral – A solid substance, usually a compound, which is found in rocks. rock – A mixture of minerals. transportation – Movement of rock fragments from one place to another. weathering – The breakdown of rocks into smaller pieces by physical, chemical and biological processes.

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200529 of 30 Anagrams

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200530 of 30 Multiple-choice quiz

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