Chemical Earth Notes

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Chemical Earth
1. The living and non-living components of the Earth contain mixtures. Identify the difference between elements, compounds and mixtures in terms of particle theory. An mixture is an impure substance that is, a pure substance contaminated with small amounts of one or more other substances. An element is a pure substance which cannot be separated into other simpler substances. A compound is a pure substance which can be decomposed into simpler substances e.g. elements. Identify that the biosphere, lithosphere, hydrosphere and atmosphere contain examples of mixtures of elements and compounds. The biosphere consists of atmosphere, lithosphere and hydrosphere. The atmosphere contains mixture of gases, and mainly the mixture of nitrogen, oxygen and argon and contains small amounts of gaseous compounds e.g. water, carbon dioxide, nitrogen dioxide, sulphur dioxide and carbon monoxide. The lithosphere contains an extremely diverse variety of mixtures: - rocks: compounds of silicon, oxygen, and many metals

- sand: mainly silicon dioxide and fine dirt
- soils: clays, aluminium, silicon, oxygen, metals and decomposing animal and vegetable matter - mineral ores: oxides, sulphides, carbonates, sulfates, chlorides - coal, oil and natural gas: mixtures of compounds or carbon formed from decayed plant and animal matter Elements: iron, gold, silver, copper

The hydrosphere major component is the compound water with small quantities of elements such as oxygen and nitrogen and compounds such as carbon dioxide, sodium, calcium and magnesium chloride and sulphates. Apart from dissolved oxygen and nitrogen the mixtures of the hydrosphere contain only compounds. Identify and describe procedures that can be used to separate naturally occurring mixtures of: solids of different sizes, solids and liquids, dissolved solids in liquids, liquids and gases. Separation of solids of different sizes: Solids of different sizes can be separated by sieving Separation of solids and liquids: Solids and liquids can be separated by filtration e.g. sand from sea-water. Sedimentation is also a process of separation, decantation (pouring the liquid off and leaving the solid at the bottom undisturbed) can be done after this. Separation of dissolved solids in liquid: evaporation is a method used so that the solid is left while the liquid is evaporated. Separation of liquids: distillation can be used, it is the process in which a solution or mixture of liquids is boiled with vapour formed by being condensed back to a liquid in a different part of the apparatus, and thus separating. Fractional distillation can also be used if the boiling points of two liquids are close together. Separation of gases: Gases are generally separated by using either differences in boiling points or differences in solubilities in liquids such as water.

Identify the industrial separation processes used on a mixture obtained from the biosphere, lithosphere, hydrosphere or atmosphere and use the evidence available to: - identify the properties of the mixture used in its separation - identify the products of separation and their uses

- discuss issues associated with wastes from the processes used Separation of solids of different sizes: Solids of different sizes can be separated by sieving, separation of solids and liquids through sedimentation or decantation. Separation of dissolved solids in liquid by evaporating, separation of liquids with distillation or fractional distillation, separation of gases by using either differences in boiling points or differences in solubilities in liquids such as water. When separating salt water, that is sodium chloride (NaCl) and water (H2O), this will result in normal drinking water and table salt. 2. Although most elements are found in combinations on Earth, some elements are found uncombined Explain the relationship between the reactivity of an element and the likelihood of its existing as an uncombined element. The...
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