Chemical Earth Notes

Topics: Atom, Electron, Chemical bond Pages: 14 (3685 words) Published: August 18, 2010
8.2 Chemical Earth
8.2.1 The living and non-living components of the Earth contain mixtures * Construct word and balanced formulae equations of chemical reactions as they are encountered Combustion reaction (burning)

element + oxygen → oxide
e.g. 4Na (S) + O2 (g) → Na2O (s)

Reaction with hydrogen
element + hydrogen → hydride
e.g. Ca (s) + H2 (g) → CaH2 (s)

Reaction between an oxide and water
metallic oxide + water → hydroxide
* metallic oxide is also known as “basic oxide”
e.g. Na2O (s) + H2O (l) → 2NaOH (aq)
non-metallic oxide + water → acid
* non-metallic oxide is known as “acidic oxide”
e.g. SO2 (g) + H2O (l) → H2SO3 (aq)

Reaction between active metals and water
active metal + water (liquid or gas) → hydroxide + hydrogen gas e.g. 2K (s) + 2H2O (l) → 2KOH (aq) +H2 (g)

Reaction between acids and carbonates
acid + carbonate → salt + water + carbon dioxide
e.g. 2HNO3 (aq) + MgCO3 (s) → Mg(NO3)2 (aq) + H2O (l) + CO2 (g)

Decomposition reactions by heating
carbonates ∆H oxide + carbon dioxide
e.g. CaCO3 (s) ∆H CaO (s) + CO2 (g)
metallic oxide ∆H metal + oxygen
e.g. 2HgO (s) ∆H 2Hg (s) + O2 (g)
hydroxide ∆H oxide + water
e.g. Mg(OH)2 (s) ∆H MgO (s) + H2O (l)

Reaction between metallic oxides and acids
metallic oxide + acid → salt + water
e.g. MnO (S) + 2HCl (aq) → MnCl2 (aq) + H2O (l)
Reaction between non-metallic oxides and bases
non-metallic oxide + base → salt + water
e.g. CO2 (g) + 2NaOH (aq) → Na2CO3 (aq) + H2O (l)

Precipitation (2 solutions mixed together form a solid)
e.g. AgNO3 (aq) + HCl (aq) → AgCl (s) +HNO3 (aq)
Ag+(aq) + Cl-(aq) → AgCl (s)
* note: H+ and NO3- are not directly involved in the reaction; hence they are “spectator ions” e.g. BaCl2 (aq) + Na2SO4 (aq) → BaSO4 (s) + NaCl (aq)
Ba2+(aq) + SO4 2-(aq) → BaSO4 (s)
* Identify the difference between elements, compounds and mixtures in terms of particle theory Element – A pure substance consisting of the same type of atoms and cannot be decomposed or broken down by physical or chemical means. Compound – A pure substance consisting of 2 or more different elements chemically combined together in a fixed ratio. Mixture – An impure substance comprising of two or more pure substances which are physically mixed together. Its components can be separated by physical means (e.g. distillation, filtration). * Identify that the biosphere, lithosphere, hydrosphere and atmosphere contain examples of mixtures of elements and compounds Biosphere

The living things on Earth
* Mixtures: wood, blood, sugarcane
* Compounds: carbohydrates (or sugars), proteins, fats and vitamins * Elements: oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus, chlorine, sulphur Lithosphere
The earth’s solid outer mantle and crust
* Mixtures: metal ores, sandstone, granite
* Compounds: quartz/sand (SiO2), calcite (CaCO3)
* Elements: oxygen, silicon, aluminium, iron, calcium, sodium, potassium, magnesium Hydrosphere
The earth’s water
* Mixtures: sea water
* Compounds: water, carbon dioxide and sodium, calcium and magnesium chlorides and sulphates * Elements: oxygen, hydrogen, chlorine, sodium, magnesium Atmosphere
The mixture of gases surrounding the Earth
* Mixtures: air
* Compounds: water, carbon dioxide, nitrogen dioxide, sulphur dioxide and carbon monoxide * Elements: nitrogen, oxygen, argon
* 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
* Gases
* Assess separation techniques for their suitability in separating examples of earth materials, identifying the differences in properties which enable these separations Separation Method | Property used in separation |

Sieving | Particle size of solids |
Evaporation| Solubility |
Crystallisation| Solubility|...
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