(A consideration of the natural processes leading to soil formation. The importance of limestone products is considered

Note that sections related to rates of reaction are not included this year) by Mr. Lorimer.

     Soil is formed when rocks are weathered into small particles. These particles come together to form soil.

Types of Weathering:    

     Rocks are weathered into soil, by physical, biological, or chemical weathering. (Exfoliation is another type of weathering but I don't think you don't have to know this one in science, only in geography)

Physical

     Physical weathering is when a rock is broken into fragments, but not chemically changed. An example of physical weathering is "freeze-thaw" weathering. When temperature changes, water that goes into cracks in the rock freezes and because water expands when it freezes, it makes the cracks widen. This causes the rock to weaken physically and start to erode.

Chemical

     Chemical weathering, is when a rock is broken down because its chemical composition is changed. A common example of this is when rocks are eroded by acid rain (carbonic acid).

Biological Weathering

     Biological weathering is when roots of of plants, like trees, grows through large rocks and break them into pieces. You know when you walk down the street, you sometimes see a part of the pavement being pushed up and has cracks all over them because of the roots growing under the concrete right? Thats an example of biological weathering. Usually biological weathering starts when a seed gets into the crack of a rock and starts growing. The seed may get into the rock because of the wind carring the seed, animals carrying them and ejesting them, or a tree near the rock can start growing into the rock. 

Types of Rocks   

Rocks are classified into three classes, igneous, metamorphic, and sedimentary rock.

Sedimentary Rocks

Sedimentary rocks are rocks that from when sediment is packed together under ground, over the course of millions of years. An example of a sedimentary rock is limestone, which comes from the bodies of ancient dead sea animals, which have been churned into limestone.

Igneous Rocks

Igneous rock is formed from magma (molten rock) that then cools and recrystallizes again. The most common example of igneous rock, is granite. It forms in the hot soft layer of rock below the lithosphere, which is the outer part of the world.

Metamorphic Rocks

Metamorphic rock is made from a combination of the processes that make igneous and sedimentary rock. It is formed when grains of different rocks are pushed together, circulating water speeds up the reaction, and the pieces of rock melt and recrystalize. Then pressure forces the rocks together to make larger grains, or if pressure mainly omes from two sides, the rocks becomes layered. Some common examples of a metamorphic rock are marble, and shale.

How limestone is formed:

 Creatures from the sea often have shells and skeletons made up of calcium carbonate. Over millions of year pressure turns layers of shell and bones fragments into limestone rock. After other millions of years powerful forces raise the seabed and forms montains. This is why limestone is found inland.

Uses:

Crushed limestone is used for:

• extracting iron from iron ore
• making sodium carbonate
• making materials for road building
• making concrete

When limestone is heated it forms quicklime;

Quicklime is used for:

• making steel from iron
• neutralizing acidity in the soil
• industrial drying agent (taking humidity out of chemicals)

When limestone is heated with clay it forms cement.

Cement is:

• used to make concrete

When crushed limestone is grinded it becomes powdered limestone.

Powdered limestone:

• neutralize acidity in soil
• neutralize acidity in water
• neutralize sulphur dioxide in flue gases from power stations
• making glass

When water is added to quicklime it forms Slaked lime.

Slaked lime produces/makes/does:

• neutralizes acidity in soil in lakes affected by acid rain.
• purifying water
• making mortar
• pottery
• chemicals
• dyes
• solvents
• paints
• medicine