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Chemistry
| Term | Definition |
|---|---|
| Pure substances (example) | Substances which have a definite and fixed composition, ie, elements and compounds. |
| Compounds | Forms of matter that consist of two or more different elements that are chemically combined in a definite whole number ratio. |
| Mixture | Forms of matter that consist of two or more different elements which are not chemically combined and occur in any ratio. They are not chemically combined and are able to be separated by physical techniques, eg filtration, distillation or chromatography. |
| Hetereogeneous (example) | Mixed unevenly -eg. Concrete, orange juice, clay, wood |
| Homogeneous | Mixed evenly-eg. Air, sea water, soft drinks, brass, these are also known as solutions |
| Common properties of pure substances (hint, there are 5) | Fixed composition- cannot be separated by physical means Constant boiling and melting points Fixed density Well-defined and constant chemical properties |
| Sieving | Separating components of a mixture based on particle size. Mixture is passed through a mesh that filters out larger particles depending on the size of the mesh. |
| Filtration and evaporation | Separates the substances in a mixture based on their differing solubility and volatility. While sieving and filtering are similar, the size of the holes are different. (normal filtration paper has a hole size of 2-25 micrometers) |
| Microfiltration | Separates substances in a mixture based on their size. Microfiltration uses a hole size of 100-1000 nanometers. Can filter muddy particles and microorganisms like bacteria and protozoa. |
| Ultrafiltration and nanofiltration | Used to filter smaller particles and viruses, molecules and ions. Pore size 0.5-5 nanometers. |
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