1.4 The Ever-Changing Earth (WJEC GCSE Chemistry): Flashcards

False.

Tectonic plates move at a rate of only a few centimetres per year, not metres.

Radioactive atoms in the Earth's core decay, releasing thermal energy that heats the mantle and causes convection currents, which slowly move the tectonic plates.

Continental drift is the slow movement of tectonic plates, which causes the continents to change position over millions of years.

The main weakness of Wegener's theory was that he could not explain the mechanism by which continental drift happened. His evidence was observational and he lacked a scientific explanation for how the continents moved.

True.

Wegener found fossils of the same plants and animals on different continents. For example, the fern Glossopteris was found in South America, Africa, Asia, Australasia and Antarctica.

Ocean floor studies revealed that rock in the middle of the ocean was younger than rock at the edges, and that no Atlantic Ocean rock samples were older than around 175 million years. This suggested new ocean floor was being created and spreading outwards.

A constructive plate boundary is a boundary where two tectonic plates move apart, allowing lava to erupt and form new igneous rock. Both volcanic eruptions and earthquakes occur here.

The only geological hazard at a conservative plate boundary is earthquakes. There are no volcanoes because the plates slide past each other and no melting occurs.

False.

Volcanoes form at constructive and destructive boundaries, but not at conservative boundaries. At conservative boundaries, plates slide past each other and no melting occurs, so no volcanoes form.

At a destructive plate boundary, plates move together and one plate is pushed down into the mantle where it melts to form magma.

A conservative plate boundary is a boundary where two tectonic plates slide past each other in opposite directions or at different speeds. Only powerful earthquakes occur here, as no melting takes place.

Scientists use the epicentres of major earthquakes and the sites of active volcanoes to identify the locations of tectonic plate boundaries, as these events occur at the edges of plates.

The Mid-Atlantic Ridge is an example of a constructive plate boundary. The boundary between the Nazca plate and the South American plate is an example of a destructive plate boundary.

True.

At destructive plate boundaries, one plate is forced beneath another into the mantle where it melts. The resulting magma rises to produce explosive volcanoes.

The Earth's early atmosphere consisted mainly of carbon dioxide and water vapour, along with nitrogen, hydrogen, and small amounts of ammonia and methane. There was little or no oxygen present.

True.

The early atmosphere consisted mainly of carbon dioxide and water vapour, which is similar to the present-day atmospheres of Venus and Mars.

Carbon dioxide levels in the early atmosphere decreased because CO₂ dissolved in the oceans, was used in photosynthesis by plants and algae, and became locked up in sedimentary rocks and fossil fuels.

Fractional distillation is the process used to separate the useful gases in air, such as nitrogen, oxygen, neon and argon, by exploiting their different boiling points.

Approximately four-fifths (about 78%) of the atmosphere is nitrogen and one-fifth (about 21%) is oxygen. The remaining gases include carbon dioxide, water vapour and noble gases.

False.

Photosynthesis is the opposite. It consumes carbon dioxide and releases oxygen. Respiration and combustion are the processes that consume oxygen and release carbon dioxide.

Combustion of fossil fuels releases carbon that was locked away millions of years ago. This adds extra carbon dioxide to the atmosphere beyond what the carbon cycle can reabsorb, disturbing the current equilibrium and increasing global warming.

In the early atmosphere, nitrogen formed when ammonia in sunlight decomposed by reacting with oxygen to produce nitrogen and water.

The greenhouse effect is the process by which greenhouse gases such as carbon dioxide trap extra heat energy from the Sun in the atmosphere, causing the Earth to warm up.

When fossil fuels are combusted, water vapour, carbon dioxide and sulfur dioxide are produced. This is because fossil fuels contain carbon, hydrogen and small quantities of sulfur.

True.

Fossil fuels contain small amounts of sulfur. When the fuel is combusted, the sulfur is oxidised to form sulfur dioxide: S (s) + O₂ (g) -> SO₂ (g).

Sulfur dioxide can be further oxidised to sulfur trioxide, which dissolves in rainwater to form sulfuric acid, a component of acid rain.

Climate change is a long-term shift in worldwide weather patterns and conditions, caused by increasing levels of greenhouse gases raising the average temperature of the Earth.

Consequences of climate change include:\n\n1. Rising sea levels (due to melting polar ice caps and glaciers)\n2. More extreme weather events such as storms, heatwaves and changing rainfall patterns\n3. Loss of habitats\n4. Increased drought

True.

Clean rain is weakly acidic with a pH of 5.5, whereas acid rain has a pH in the range of 2 to 4, making it significantly more acidic.

Acid rain damages limestone and marble structures because both materials contain calcium carbonate, which reacts with the sulfuric acid in acid rain. This causes the stonework to corrode and weaken over time.

Carbon capture and storage (CCS) is a process that reduces carbon dioxide emissions by capturing CO₂ from industrial processes, compressing and transporting it, then injecting it into rock formations deep underground for permanent storage.

True.

Fossil fuels are the source of both carbon dioxide and sulfur dioxide emissions. Using less fossil fuel reduces both gases simultaneously.

Sulfur scrubbing is a process used to reduce sulfur dioxide emissions from coal-fired power stations, in which waste gases are passed through a scrubbing chamber where a slurry of calcium oxide and calcium carbonate reacts with and removes the sulfur dioxide.

To address acid rain, farmers can add lime to soil to reduce its acidity. Weak alkalis can also be used to neutralise rivers and lakes affected by acid rain.

Three ways individuals can reduce carbon dioxide emissions include:\n\n1. Using renewable energy such as solar or wind power instead of fossil fuels\n2. Using public transport or car-sharing to reduce vehicle use\n3. Reducing household energy consumption by turning off lights and using efficient appliances

False.

Carbon capture and storage (CCS) is only carried out on a large scale, for example in coal or natural gas fired power stations and in steel or cement factories.

The three steps in CCS are:\n\n1. Capture, where CO₂ is separated from other waste gases\n2. Transport, where the CO₂ is compressed and moved by pipeline, road or shipping\n3. Storage, where the CO₂ is injected into rock formations deep underground

In sulfur scrubbing, waste gases are sprayed with a slurry containing calcium oxide and calcium carbonate. These react with sulfur dioxide to produce calcium sulfate.

Limewater is an aqueous solution of calcium hydroxide used as a chemical test for carbon dioxide. Carbon dioxide turns limewater milky or cloudy.

To test for carbon dioxide, bubble the gas through limewater (aqueous calcium hydroxide). A positive result is that the limewater turns milky or cloudy.

True.

The test for oxygen uses a glowing splint placed into a test tube of gas. If oxygen is present, the splint relights.

To test for oxygen, place a glowing splint into the gas. If oxygen is present, the splint will relight.

False.

Extinguishing a burning splint only shows there is insufficient oxygen to keep the flame going. Other gases such as nitrogen would also do this, so it is not a definitive test for carbon dioxide.

To test for oxygen, place a glowing splint into a test tube of the gas. A positive result is that the glowing splint relights.

Extinguishing a burning splint is not a valid test for carbon dioxide because it only shows a lack of sufficient oxygen. Other gases such as nitrogen would also extinguish the flame, so this result is not specific to carbon dioxide.