Physical and Chemical Weathering of Rocks

Weathering of rocks is a physical or chemical change that changes the characteristics of rock on earth

There are two major types of weathering.

Chemical weathering changes which involve rocks being changed into new substances or new minerals chemically.

Physical weathering which involves breaking rocks into smaller fragments caused by environmental factors.

Three major types of physical weathering

• Abrasion
• Frost Wedging
• Thermal stress

Abrasion is a mechanical scraping and can be caused by the following factors.

• Wind
• Water /waves
• Glaciers
• Gravity
• Plants/animals

Frost wedging occurs as water expanding as it freezes causing the rock to break apart.

Thermal stress results when heat and changes in temperature cause rock to expand and contract and this can break the rock apart.

Chemical changes occur when a chemical reaction creates a new substance.

Oxidation occurs as oxygen o2 combines with iron in rock and creates new compounds.
When iron reacts with oxygen, it forms iron oxide commonly called rust, which weakens the rock.

Hydrolysis occurs when hydrogen reacts and creates a new substance.
For example, Hydrolysis causes feldspar to turn into clay.

Carbonation is the process of mixing water with carbon dioxide to make carbonic acid. This acid then breaks down and weakens rocks. Caves may be formed by carbonation dissolving limestone. Rainwater picks up carbon dioxide from the air and as it percolates through the soil slowly dissolves out the limestone.

Helpful Resources on weathering

Weathering Playlist

Weathering Crossword Puzzle

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The Mohs Scale of Hardness Explained

The Mohs scale of mineral hardness is based on the ability of one mineral to scratch another mineral visibly. The Mohs' hardness scale was developed in the 1800s by Frederich Mohs, a German mineralogist. Hardness is a measure of a mineral’s ability to resist being scratched. He selected ten minerals of different hardness that ranged from a very soft mineral (talc) to a very hard mineral (diamond). When completing hardness tests of the minerals it is necessary to determine which mineral was scratched.

Let’s go through the Moh’s Scale As you move up the scale hardness increases 1 Talc 2 Gypsum 3 Calcite 4 Fluorite CaF2 5 Apatite 6 Orthoclase feldspar 7 Quartz 8 Topaz 9 Corundum 10 Diamond You can also use common household items to test for hardness.

A fingernail 2-2.5
Penny 3.5
Nail 5-6
Glass 5- 5.5
Streak plate 6 6.5
Quartz 7

 Let's determine the hardness of a mineral. The mineral can scratch talc so it has a hardness greater than 1. However, the mineral can be scratched by calcite which has a hardness 3 so its hardness is 2. Now I can use this information, along with a mineral field guide in order to identify the mineral.

Additional Mohs Scale Resources

Mohs scale on Youtube

Helpful Article

A very detailed list of Mineral and Hardness

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Practice Identifying Minerals

This chart goes along with the video identifying minerals.

Use this blank chart during the video in order to record data.

Number	Color	Luster	Streak Color	Hardness	Reaction with Vinegar	Magnetic

Use this chart in order to identify the minerals based on physical properties.

Mineral	Color	Luster	Streak Color	Hardness	Reaction with Vinegar	Magnetic
Feldspar	White Red Green	Glassy Vitreous	White	6	No	No
Hematite	Red, Black Brown	Dull metallic	red	5.5 6	No	No
Pyrite	Brass Yellow	metallic	brown	6	No	No
Quartz	No color White	Glassy vitreous	none	6.5  7	No	No
Mica	No color Yellow	glassy	none white	2	No	No
Magnetite	Black	metallic	black	6	No	Yes
Calcite	white	Glass vitreous	white	2.5 3	Yes	No
Talc	White Green Gray	Greasy pearly	white	1	No	No

Answer Key

Mineral #1 Talc

Mineral #2  Magnetite

Mineral #3 Mica

Mineral #4 Calcite

Mineral #5 Quartz

Mineral #6 Pyrite

Mineral #7 Feldspar

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Relationship between Photosynthesis and Cellular Respiration

Wouldn't it be nice if you could take the exhaust of your car and used it as fuel for your motorcycle and the exhaust of your motorcycle and use it for fuel your car? This would have a nice cycle in which both the car and motorcycle benefit.
Photosynthesis and cellular respiration have a similar relationship.  The products of photosynthesis are used in cellular respiration and the waste products of cellular respiration is fuel for photosynthesis.
In order to stay alive we need to eat. Do plants need food?
How do plants get food by just standing around all day? Plants get their energy using a process called photosynthesis. In order for photosynthesis to take place a plant needs three items, water, carbon dioxide and sunlight. 

How does photosynthesis work?
Plants have small openings called stomata on their surfaces.
Carbon dioxide in the atmosphere enter these tiny openings and travel to the chloroplasts.
Photosynthesis occurs at the chloroplasts when plants take carbon dioxide plus water and energy from the sun and in a chemical reaction creates sugar in the form of glucose and oxygen.
The sugar created during photosynthesis is used by the plant to create energy and the oxygen is released into the atmosphere.
You can define photosynthesis as the process by which plants and other things make food. It is a chemical process that uses sunlight to turn carbon dioxide and water into sugars that the cell can use as energy.
Why is cellular respiration important? It is important because  living organisms must generate energy for their daily activities. Cellular respiration provides this energy.
Cellular respiration takes place at the mitochondria. Think of the mitochondria as a power plant for cells similar to how cities use power plants for energy.
At the mitochondria the sugar in the form of glucose combines with oxygen to produce carbon dioxide, water and energy in the form of ATP.

In summary, photosynthesis takes carbon dioxide and water plus sunlight to create oxygen and sugar which is exactly what cellular respiration needs.
 Cellular respiration takes the sugar and oxygen to create carbon dioxide and water plus ATP which helps with photosynthesis.
This cycle repeats over and over again.

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Rock Cycle Diagram

The Rock Cycle


As Twisted Sister may say, "I wanna Rock! Rock! Rock! rock the Rock Cycle.
The Earth is constantly changing and the rock cycle is one of many cycles like the water, carbon, and nitrogen that recycles important resources on Earth.
There are three main rocks involved in the rock cycle.

• Igneous
• Sedimentary
• Metamorphic

Igneous rocks are created from molten rock. In fact, the name is derived from a Greek word for fire.
Igneous rocks form from hot, molten rock that cools and then solidifies. Igneous rocks may form from magma which is found inside the Earth or Lava which is a molten rock on the surface of the Earth.
There are two major types of igneous rocks
Intrusive igneous rocks have large crystals because they cool slowly inside the Earth.
Extrusive igneous rocks have small crystal or no crystals at all because they cool quickly.

Sedimentary rocks are the most common rocks on Earth
Many of these rocks are created by weathering, erosion, deposition, compaction, and cementation.
You can use WEDCC in order to help you understand this process.

Metamorphic rocks are created when extreme heat and pressure change the original structure into a new type of rock sedimentary igneous and even metamorphic rocks can all become
metamorphic rocks when exposed to heat and pressure. the original rock is referred to as the
protolith but it's commonly referred to as the parent rock.

Contact metamorphism occurs when the existing rock comes into contact with extreme heat like magma inside the earth and becomes something new

Regional metamorphism is caused by extreme pressure. The pressure presses and squeezes the rock and transforms it. Kinda like gravity acts on this balloon. This will occur at convergent plate boundaries. Existing rocks are transferred into new rocks at these boundaries.

When you look at the rock cycle the arrows point to what the rock is becoming.

• In order for any rock to become a metamorphic rock heat and pressure needs to be applied.
• In order to become sedimentary rock, it must go through WEDCC.
• In order to become an igneous rock, it needs to melt, cool, then become solid.

The rock cycle is a never-ending cycle of rocks changing from one form to another.

Rock Cycle Resources

Rock Cycle Video

Rock Cycle Article

Rock Cycle Quizlet

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Clastic Sedimentary Rocks

Sedimentary rocks are derived from igneous, sedimentary and metamorphic rocks.
Sedimentary rocks make up around 75 percent of the rocks at the earth's surface.
Let’s take a look at how clastic sedimentary rocks form. Clastic sedimentary rocks are the group of rocks most people think of when they think of sedimentary rocks. Clastic sedimentary rocks are made up of pieces of pre-existing rocks called clasts.

These sedimentary rocks follow WEDCC in order to form.

Weathering

Erosion

Deposition

Compaction

Cementation

Weathering occurs when preexisting rocks are broken down. This may occur by freezing and thawing of water inside cracks in a rock, trees and other plant roots growing into cracks, and blowing winds that create the friction that breaks down the rock.

Erosion occurs when these clasts of rocks created during weathering are transported by wind water or even gravity to a new location.

Deposition is when the particles are deposited as loose sediment. Usually near a body of water.

Compaction occurs as layers of deposition build on top of one another and begins to squeeze closer together.

Cementation occurs eventually the minerals in the water will act like glue and cement together.
The end result is a sedimentary rock.

This process of loose sediment hardening into a rock is collectively called Lithification. It includes compaction and cementation.

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Igneous rock Textures

Phaneritic igneous rocks have crystals larger than 1 mm. You could describe the texture as coarse because of the larger crystals.

Aphanitic texture  The name tells you about this texture.
a = not
Phaner = visible
These rocks have very fine small crystals that are smaller than 1mm in size.

Porphyritic igneous rocks have distinct differences in the size of the crystals, with at least one group of crystals obviously larger than another group.

Glassy rocks look like the name suggests no crystals and the texture of glass.

Vesicular are igneous rocks with bubbles created when these rocks cooled very quickly. Vesicular rocks can be mafic or felsic in color.

Pyroclastic rocks are a mixture of rock fragments, pumice, and volcanic ash. The ash is very fine-grained, so only the rock fragments and pumice are identifiable. A rock with a pyroclastic texture is termed a tuff if it has small fragments, and breccia if the fragments are larger in size.

In summary
6 Igneous Rock Textures 

Phaneritic: Large crystals

Aphanitic: Small crystals

Porphyritic: Different sized crystals

Glassy: Look like glass

Vesicular: Have bubbles

Pyroclastic: Rock fragments

Igneous Rock Playlist

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