Chemical Weathering Quiz

Chemical Weathering

• Chemical weathering breaks down rocks through reactions with water, gases, or acids.
• This process reshapes landscapes and influences global climate patterns.

Vocabulary

• Chemical Weathering: The breakdown of rocks through chemical reactions, often involving water, gases, or acids.
• Carbon Dioxide (CO2): A greenhouse gas that traps heat in the atmosphere and plays a role in weathering when dissolved in water.
• Carbonic Acid (H2CO3): A weak acid formed when CO2 dissolves in water, contributing to the chemical breakdown of rocks.
• Oxidation: A chemical reaction where minerals in rocks react with oxygen, often resulting in rust.
• Dissolution: The process by which minerals dissolve in water.
• Enhanced Weathering: A technique where crushed rocks are spread over land to accelerate the weathering process.

Tombstone Damage

• Students discuss the reasons why the lettering on a tombstone is no longer readable.
• Possible causes include rain softening the stone, leading to erosion, damage by people, the age of the stone, the sun fading the letters, and rain chemically reacting with the stone.

Rain pH

• Natural rainwater has a pH of approximately 6.5.
• Polluting gases in the air, like carbon dioxide, make rainwater more acidic.

Timescales

• The chemical weathering of a tombstone typically takes place over a long period, not a short timescale like minutes or seconds.
• The timescale of chemical weathering can be 100 years.

Chemistry of Weathering

• Oxidation: Oxygen reacts with minerals, causing rust. Iron-rich rocks turn reddish-brown as a result.
• Dissolution: Acidic water dissolves minerals. Limestone caves form through this process.
• Hydrolysis: Water breaks down minerals. Feldspars in granite decompose to form clay minerals.

Weathered Statues

• Rainwater causes chemical weathering of limestone buildings such as statues.
• The damage to the statues at Wells Cathedral serves as an illustrative example.
• Students speculate on how rain chemically destroys statues. A common view is that rain dissolves the limestone. Another view is rain reacts with the limestone to create a new substance that dissolves.

Weathering Differences

• Two statues, one of limestone and the other of sandstone, are compared.
• The limestone statue is expected to weather more due to its susceptibility to acidic reactions.
• The type of mineral from which the statue is composed determines its susceptibility to weathering. The difference is due to the fact that the mineral in limestone reacts more quickly with acid than the mineral in sandstone.

CO2: The Invisible Weathering Agent

• Atmospheric CO2 dissolves in rainwater, creating weak carbonic acid.
• Carbonic acid reacts with rocks, particularly limestone. This reaction releases minerals and stores carbon in soil and other geological formations.

Human Impact on CO2 Levels

• Burning fossil fuels (coal, oil, and natural gas) increases atmospheric CO2 levels.
• Deforestation reduces nature's ability to absorb CO2.
• Rising CO2 levels intensify the greenhouse effect, leading to global climate changes. Trends in CO2 levels are shown in a graph.

Burning Methane

• Methane is a fossil fuel. It is also used in Bunsen burners.
• Burning methane in gas-fired power stations releases carbon dioxide.
• When methane burns, carbon atoms combine with oxygen in the air to form carbon dioxide.

Carbon Dioxide Molecules

• Carbon dioxide is produced when petrol burns in a car engine.
• Carbon dioxide molecules leave through the car's exhaust pipe and mix with other molecules in the surrounding air.

Thinking About Combustion

• Students are asked to explain why carbon dioxide is produced when methane burns.
• Students use different ways of thinking to explain the formation of carbon dioxide. A suitable and correct approach is to emphasize the chemical composition of fuels. A student might note that when a substance burns (in this instance methane), it chemically combines with oxygen, which is a necessary component.
• Ways of thinking that might hinder comprehension might be considering the shape of the molecules, or just noting the presence of carbon in the substance without clearly stating that carbon atoms combine with oxygen atoms present in the air during the process.

Measuring Carbon Dioxide

• The graph displays the increase in atmospheric carbon dioxide from 1960 to 2021.
• Measurements from a specific observatory are tracked over time.

Carbon Dioxide Removal

• Photosynthesis is a process involving atmospheric carbon dioxide uptake.
• Dissolving is another process for carbon dioxide removal from the atmosphere.

Chemical Weathering and Climate Change

• Chemical weathering processes naturally remove atmospheric CO2.
• Warmer temperatures increase weathering rates.
• Climate affects the rate of weathering, creating a complex feedback loop.

Warming Oceans

• An increase in water temperature decreases the rate at which carbon dioxide dissolves in the oceans.

Changing Levels of CO2

• The rate at which carbon dioxide is added to the atmosphere is greater than the rate at which it is removed.
• Reducing the rate of addition of carbon dioxide to the atmosphere could lower levels.

What Dissolves?

• Salt, sugar, and copper sulfate dissolve in water, but gases like oxygen and carbon dioxide do not dissolve in water as readily.

Fizzy Water

• The amount of fizz and how much carbon dioxide is released from a bottle of water depends on the temperature of the water. Cooler water is able to hold more carbon dioxide than warmer water.
• This means colder water is capable of releasing more carbon dioxide after initial opening.

Reversing Climate Change: Nature and Technology

• Reforestation: Planting trees absorbs CO2.
• Enhanced weathering: Spreading crushed rocks accelerates CO2 absorption.
• Carbon capture: Technology removes CO2 from emissions.
• Renewable energy reduces CO2 emissions.