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1. ClassAct SRS enabled. • In this presentation you will: • Explore the distillation process and the different types of distillation.

2. Distillation is a widely used method for separating mixtures. It can be used for separation, purification, or removal of a solvent. Next >

3. Molecules undergoing vaporization Vaporization To understand the distillation process we need to look at the concepts of vaporization, condensation and boiling point. When heat is added to a liquid, some of its molecules acquire enough kinetic energy (movement) to escape the surface of the liquid and become gas or vapor. This is known as vaporization. Next >

4. Molecules undergoing vaporization Molecules undergoing condensation Condensation If the same liquid is in a container with a lid, the vapor molecules will remain in the container. With time, the air above the liquid saturates and although it looks like nothing is happening, the molecules keep moving. Some molecules keep becoming vapor but, at the same time, some vapor molecules make contact with the liquid and get trapped by it, returning to the liquid state. This process is called condensation. Next >

5. Question 1 The process where liquid becomes gas is called: A) Vaporization. B) Condensation. C) Boiling point. D) Distillation.

6. Question 2 The process where gas returns to the liquid state is called: A) Vaporization. B) Condensation. C) Boiling point. D) Distillation.

7. Boiling Point When a liquid is in an opened container, the atmospheric pressure opposes the escape of the molecules of the liquid. When the liquid is heated, the vapor pressure increases. If we continue heating the liquid, the vapor pressure becomes equal to the atmospheric pressure. This is the temperature where the liquid will start boiling and is called the boiling point. Next >

8. 8800 meters high, water boiling point = 71°C Sea level, water boiling point = 100°C Normal Boiling Point Since the atmospheric pressure changes due to the altitude and the meteorological conditions, the boiling point of a liquid differs for different liquids. Those same liquid boiling points will also differ on different parts of the Earth. It is for this reason that the normal boiling point is defined as the temperature at which a liquid boils at standard atmospheric pressure (1 atmosphere). Next >

9. Question 3 The boiling point is where: A) the vapor pressure is lower than the atmospheric pressure. B) the vapor pressure equals the atmospheric pressure. C) the point before the liquid starts boiling. D) the point after the liquid starts boiling.

10. Question 4 The atmospheric pressure always decreases with increasing height. Which of the following is true? A) When the altitude increases the boiling point increases. B) When the altitude increases the boiling point decreases. C) The change in altitude does not affect the boiling point.

11. Simple Distillation In simple distillation, to separate a mixture of liquids, the liquid can be heated to force components, which have different boiling points, into the gas phase. The gas is then condensed back into liquid form and collected. Next >

12. Simple Distillation Imagine a mixture of water and a non-volatile material like common salt. If the mixture is heated until it boils, the water would be evaporated but not the non-volatile material. The water vapor condenses. It returns to a liquid state and collects in a container. The vapor obtained this way is called the distillate. In this case the distillate is pure water. Next >

13. Question 5 The boiling point of water is 100° C (212° F) and that of alcohol is 78.5° C (173° F). Which substance will vaporize first in the distillation process? A) Water B) Alcohol C) Both at the same time. D) Neither water nor alcohol would vaporize.

14. Fractional Distillation A typical lab fractional distillation setup would be like that in the picture opposite. The fractionating column is packed with glass beads (or something similar) to give the maximum possible surface area for vapor to condense on. The mixture is heated so that the thermometer shows the temperature of the boiling point of the more volatile component. That vapor now starts to travel up the fractionating column. Eventually it will reach a height in the column where the temperature is low enough that it will condense to give a liquid. Next >

15. Fractional Distillation It will start to run back down the column where it will meet new hot vapor rising. This will cause the condensed vapor to vaporize again. This new vapor will again move further up the fractionating column until it gets to a temperature where it can condense. Then the whole process repeats itself. Each time this happens the new vapor will be richer with molecules of the more volatile component. The aim is to balance the temperature of the column so that by the time vapor reaches the top, it consists only of the more volatile component. This will then escape the column and condense. Next >

16. Fractional Distillation The most important industrial application of fractional distillation is the distillation of crude oil. The crude oil is heated until it vaporizes. The vapors pass up a fractionating column, which is kept very hot at the bottom and cooler towards the top. The fractions with the lowest boiling point boil off first and rise to the top of the tower. The fractions with the highest boiling point condense first. Next >

17. Fractional Distillation The liquid formed is collected in a series of trays containing bubble caps. The bubble caps force the rising vapors to pass through the liquid in the tray. The vapors condense to a liquid when they arrive at a tray that is sufficiently cool. The liquids are then piped off separately. Next >

18. Question 6 Which property allows separating the components of a mixture in the fractionating column? A) The vaporization process. B) The condensation process. C) The different boiling points of the components. D) The height of the column.

19. Destructive Distillation In destructive distillation a material is usually heated so that it decomposes into compounds for collection. Destructive distillation is a chemical change. For example, in the distillation of wood, the end product (charcoal) cannot be turned back into wood. Next >

20. Summary After completing this presentation you should be able to : • Show knowledge and understanding about vaporization, condensation and boiling point. • Show knowledge and understanding about the distillation process. • Show knowledge and understanding about fractional and destructive distillation. End >