The Earth includes a clearly identifiable biosphere, lithosphere, hydrosphere and atmosphere. All of these are mixtures of thousands of substances and the use of this pool of resources requires the separation of useful substances. The processes of separation will be determined by the physical and chemical properties of the substances.
In order to use the Earth’s resources effectively and efficiently, it is necessary to understand the properties of the elements and compounds found in mixtures that make up earth materials. Applying appropriate models, theories and laws of chemistry to the range of earth materials allows a useful classification of the materials and a better understanding of the properties of substances.
This module increases students’ understanding of the nature, practice, applications and uses of chemistry.
8.2.1 The living and non-living components of the Earth contain mixtures
.2.1 a) Construct word and balanced formulae equations of chemical reactions as they are encountered Method:
1. Identify reactants, products and reaction conditions
2. Write reactants and products with formulae (note valency numbers and balance electric charges) 3. Balance equation using laws of conservation of mass
.2.1 b) Identify the difference between elements, compounds and mixtures in terms of particle theory Atom: The smallest particle that cannot be divided by any physical or chemical means Molecule: Two or more atoms (the same or different) that are chemically bonded together Lattice: 3D array of oppositely charged particles (ions) held together by an electrostatic attraction Element: Consists of only one type of atom
Compound: Composed for two or more elements that are chemically bonded together. Contains a fixed number of atoms of each component element. Pure Substance: Have a fixed composition and fixed properties (for that specific substance). Cannot be decomposed by physical separation methods. Mixtures: Have variable composition and variable properties. Can be separated into components by physical separation methods.
* Elements are composed of atoms or molecules
* Compounds are composed of a fixed number of atoms of different elements * Mixtures have various particle types and compositions
* Homogenous mixtures Particles are distributed uniformly (E.g. glass, salt water – appears the same by naked eye) * Heterogeneous mixtures Not distributed uniformly
.2.2 Identify that the biosphere, lithosphere, hydrosphere and atmosphere contain examples of mixtures of elements and compounds Lithosphere
Rocks and weathering products (soil). Mixtures of minerals. * Minerals naturally occurring crystalline solid that has a fixed chemical composition (element or compounds) * Combined in different proportions to form sedimentary, igneous and metamorphic rocks * Examples:
* Compounds: Sand – silicon dioxide, Extraction of metals from minerals (aluminium from compounds) * Elements: Gold
* Mixtures: Mud
* Most abundant: oxygen and silicon at crust, iron because of core. Hydrosphere
Water with varying quantities of particles of chlorine, sodium, magnesium etc. * Most abundant: water (Hydrogen and oxygen)
- Mixtures: Salt water
Mixture of uncombined light elemnts
* Most abundant: Nitrogen (78%) and oxygen (21%)
* Compounds: Carbon dioxide
* Elements: Oxygen molecules
Living things: composed for many common chemical characteristics and Carbon as a basis * Most abundant: Oxygen and hydrogen (because of water in cells of living organisms) * Examples:
* Compounds: Carbon compounded basis for life (CHO, fats, proteins, nucleic acids)
.2.3 Identify and describe procedures that can be used to separate naturally occurring mixtures of: * Solids of different sizes