The Chemical Earth
K184.108.40.206 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.
K220.127.116.11 identify that the ...view middle of the document...
It has a varied composition (i.e., salt and fresh water), and is mainly made up of the compound water (H2O) but also contains many water soluble sulfates and soluble carbonates, and elements like chlorine and sodium dissolved as ions.
K18.104.22.168 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
K22.214.171.124 assess separation techniques for their suitability in separating examples of earth materials, identifying the differences in properties which enable these separations
Separation Procedures: - usually separations require a number of processes or procedures to separate the constituent substances from a mixture. These separations are physical separations.
• Filtration – separates undissolved solids from liquids or gases by passing the mixture through a screen such as filter paper which is fine enough to collect the particles of the solid.
• Solution – usually used in combination with another separation method, and is based on the fact that some constituents in a mixture dissolve in a solvent such as water more readily than others. That is, a mixture is added to a solvent and can be separated through the fact that one constituent will dissolve more readily than the others (although to fully separate the mixture, another method such as filtration would have to be used).
• Evaporation – relies upon the varying evaporating points of the constituent substances within a mixture. A mixture is heated (in an evaporating basin and the process is usually sped up using a Bunsen burner) and one substance will evaporate, leaving the other substance behind.
• Crystallisation - depends on the components of the mixture having different solubilities in a selected liquid (usually water) at different temperatures. For example, a mixture of salt and baking powder are both soluble in hot water, but when the hot water (with the mixture dissolved in it) is cooled, the baking soda will crystallise because it is much less soluble at cooler temperatures.
• Sedimentation – occurs when solid particles are allowed to settle from water (or other liquids) or air. This occurs most readily when the solvent is not moving.
• Decantation – the process of pouring off a liquid above a solid which has been allowed to settle by sedimentation.
• Sieving – the process of separating solid particles of various sizes.
• Centrifugation – involves a centrifuge that spins and separates solids and liquids.
• Distillation – is effective where the constituent substances of a mixture have very different boiling points. The mixture is heated and the substance with the lowest boiling point boils, is cooled in a condenser and is collected as a pure liquid. The components with the higher boiling points remain in the distilling flask. Fractional distillation is also used to...