Mixtures solutions and pure substances

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Mixtures solutions and pure substances

  1. 1. MIXTURES, SOLUTIONS AND PURE SUBSTANCES
  2. 2. Matter and its appearance According to its appearance, there are two kinds of material systems:  Homogeneus systems: they have the same properties and compositions in all different parts of them.  Heterogeneus systems: different parts with different properties can be found in them.
  3. 3. Homogeneus Systems
  4. 4. Heterogeneus Systems
  5. 5. Heterogeneus Mixtures Systems with several different substances that can be distinguished:  Oil and water.  Granite is a rock that has three different substances: quartz, mica and felspar.  Blood: using a microscope we can see a liquid (plasma) and different kinds of cells.  Smoke: has solid particles in a gas (air).
  6. 6. Heterogeneous Mixtures How to separe their components: – If the components are a solid and a liquid, we can separe them by filtering. • E. g.: water and sand
  7. 7. Heterogeneous Mixtures How to separe their components: – Decantation: This method uses the different densities of the components to separe them: • (E.g.: oil and water)
  8. 8. Homogeneous Systems There are two kinds of homogeneous systems:  Pure substances: • They have an only component • They have constant composition and properties.  Solutions: • They have several components. • Their composition can be changed
  9. 9. Solutions A solution has, at least, two components:  Solute:  It is the component that is present in a lower quantity in the solution.  Solvent:  It is the component that is present in excess.  Its state never changes when the solution is being formed A simple sample: salty water:  There is much more water than salt  Water is a liquid and the solution too.  SOLUTE = SALT and SOLVENT = WATER
  10. 10. SolutionsThey are not always liquids
  11. 11. Solutions There three kinds of solutions:  Solvent + a small amount of solute = diluid solution.  Solvent + a large amount of solute = concentrate solution.  The quantity of solute that can be dissolved has a limit (solubility). In this case we have a satured solution.  If we try to dissolve more solute in a satured solution, the extra quantity of solute will fall onto the botton of the container. (precipitation)
  12. 12. SolutionsConcentration of a solution: – Expresses, in a numeric way, the quantity of soluto un a specific quantity of solution. amountofsoluto concentration= amountofsolution There are many ways of express it, depending of the unit we use. We are going to study three of them.
  13. 13. Solutions Concentration: grams per liter of solution. massofsoluto ( g ) concentration ( g / L )= VolumenofsolutionSample: we put 20 grams of sugar in a 500-mililiters flaskand fill it in with water.In the flask, there are: 20 g of soluto (sugar) Soluto and solvent with a total volume of 500 mL = 0,5 L concentration (g/L) = 20 g / 0,5 L = 40 g/L
  14. 14. Solutions Concentration: percentage in mass massofsoluto concentration ( mass )= · 100 massofsolutionSample: we add 25 grams of salt into a flask that contains100 grams of water.In the flask, there are: 25 g of soluto (salt) 100 g + 25 g = 125 g of solution (salt + water) % mass = (25 g / 125 g) · 100 = 20 % in mass
  15. 15. Solutions Concentration: percentage in volume volumeofsolutoconcentration ( volume )= · 100 volumeofsolution Sample: we mixure 20 mililiters of alcohol and 130 mililiters of water: We have: 20 mL of alcohol (alcohol) 130 mL + 20 mL = 150 mL of solution (alcohol + water) % mass = (20 mL / 150 mL) · 100 = 13.3 % in volume
  16. 16. Solutions How to separate its components: – Evaporation and crystallization: a liquid evaporates at room temperature, but a solid doesnt.
  17. 17. Solutions How to separate its components: – Distillation: this method is useful to separate: • Liquids whose boiling points are different enough • Liquids and solids
  18. 18. Pure Substances Pure substances:  They have a constant composition.  They cant be separated in simpler substances using physical methods. There are two different kinds of pure substances:  Chemical compounds: pure substances that can be separated in others using chemical methods.  Elements: pure substances that cant be separated in others
  19. 19. Compound Pure substance composed of two or more different elements joined by chemical bonds.  Made of elements in a specific ratio that is always the same  Has a chemical formula  Can only be separated by chemical means, not physically There are millions of different compounds in nature
  20. 20. Compound ¿Compound or Mixture?
  21. 21. Element It is the simplest kind of matter.  Has a chemical symbol.  Cant be separated in others substances There are only about one hundred elements in natures. All of them are in the Periodic Table
  22. 22. Four kinds of matter
  23. 23. Four kinds of matter
  24. 24. Four kinds of matter

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