Changes to the atmosphere
Carbon dioxide is a very Able to dissolve in solvent. For example, sugar is soluble in water because it dissolves to form sugar solution. gas. It When a substance breaks up and mixes completely with a solvent to produce a solution. readily in water. As the oceans formed, carbon dioxide dissolved to form soluble Substance containing carbonate ions. Most carbonates are insoluble (such as calcium carbonate) but sodium carbonate and ammonium carbonate are soluble in water. A substance formed by the chemical union of two or more elements. so the amount in the The layers of gases that surround the Earth. The important gases in the atmosphere are nitrogen, oxygen and carbon dioxide. decreased. Carbonate compounds were then A suspension of particles in a liquid formed when a dissolved substance reacts to form an insoluble substance, eg in a precipitation reaction. as Rocks that are formed through the deposition of sediments, eg limestone and sandstone. rocks, eg limestone.
Carbon dioxide was also absorbed from the oceans when the first plants and A group of organisms that photosynthesise but lack the complex range of cell types and organs found in land plants. Most algae are aquatic. All have chloroplasts. carried out A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic.. Many of these Living entity, eg animals, plants or microorganisms., and those in the food chains that they supported were turned into fossil fuels, eg Mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms., coal and A naturally occurring hydrocarbon gas mixture., which all contain carbon.
Crude oil and natural gas were formed from simple plants and tiny animals which were living in oceans and lakes. These small organisms died and their remains sank to the bottom where they were buried under sediments. The lack of oxygen prevented oxidation from occurring.
Over millions of years, heat and pressure turned the remains of the organisms into crude oil and natural gas. Natural gas contains the smallest molecules and is often found on top of crude oil, trapped under sedimentary rock.
Question
Describe two reasons why the amount of carbon dioxide in the atmosphere decreased over time.
Carbon dioxide dissolved in the oceans and primitive plants/algae used it for photosynthesis.
Plants make their own food by photosynthesis. In this process, carbon dioxide is reacted with water to produce glucose, with oxygen as a Something that is produced as a waste product.:
carbon dioxide + water 鈫 glucose + oxygen
6CO2+ 6H2O鈫 C6H12O6+ 6O2
Scientists think that algae first evolved approximately 2.7 billion years ago, and soon after this oxygen began to exist in the atmosphere. Photosynthesis by primitive plants and algae released oxygen, which gradually built up in the atmosphere.
Eventually, the amount of oxygen present in the atmosphere enabled animals to evolve. Photosynthesis also decreased the amount of carbon dioxide present in the atmosphere.
