The Chemical Earth

The Chemical Earth

K8.2.1.1 identify the difference between elements, compounds and mixtures in terms of particle theory: The particle theory:

  1. Matter is made of tiny particles

  2. Particles of matter are in constant motion

  3. Particles of matter are held together by very strong electric forces

  4. There are empty spaces between the particles of matter that are very large compared to the particles themselves.

  5. Each substance has unique particles that are different from the particles of other substances

  6. Temperature affects the speed of the particles.  The higher the temperature, the faster the speed of the particles.

K8.2.1.2 identify that the Biosphere, Lithosphere, Hydrosphere and Atmosphere contain mixtures of elements and compounds.

    • Biosphere – consists of all living organisms and their life cycles. The most abundant elements are oxygen (60%), carbon (21%) and hydrogen (11%), which are mostly found within the DNA of living things and organic compounds such as amino acids, carbohydrates, fats and proteins.

    • Atmosphere – is the layer of gas surrounding the earth and is a mixture composed mostly of un-combined lighter elements, although composition varies according to location or climate. The two most abundant elements are nitrogen (75.3%) and oxygen (23.2%), which occurs in their gaseous forms or in compounds like carbon dioxide.

    • Lithosphere – is made up of the crust and the solid top of the mantle, and is composed mostly of rocks and soil (mixtures of minerals), which can have a definite composition or a range of compositions. Elements such as oxygen (47%), silicon (28%), aluminium (8%) and iron (5%) occur in silicate, oxide and carbonate minerals. Pure elements such as gold also occur in their pure form (un-combined) in the lithosphere.

    • Hydrosphere – is all the water on earth and is a discontinuous sphere. It has a varied composition (i.e., salt and fresh water), and is mainly made...