GCSE Chemistry - Fractional Distillation and Simple Distillation #50

Cognito
11 May 201905:35
EducationalLearning
32 Likes 10 Comments

TLDRThis video explores two distillation methods for separating liquid mixtures: simple and fractional distillation. Simple distillation, suitable for mixtures like seawater, uses a flask, thermometer, condenser, and heating device to evaporate and condense pure liquid. Fractional distillation, necessary for mixtures with similar boiling points like methanol, ethanol, and propanol, incorporates a fractionating column with glass rods to separate components by temperature. The process is illustrated with a step-by-step guide, making it accessible and informative.

Takeaways
  • 🔬 Simple distillation is used to separate a liquid from a solution, such as obtaining pure water from seawater.
  • 🧪 The equipment for simple distillation includes a flask, a bung, a thermometer, a condenser with a water jacket, a beaker, and a heating device.
  • 🌡 The process involves heating the mixture until the desired liquid evaporates, which then travels to the condenser and condenses back into a liquid.
  • 💧 In simple distillation, the condensed liquid is collected in a beaker, leaving behind the non-volatile components like salt in the case of seawater.
  • 🤔 Simple distillation is not effective for separating mixtures of liquids with similar boiling points, such as methanol, ethanol, and propanol.
  • 🔄 Fractional distillation is the technique for separating mixtures of liquids with similar boiling points.
  • 🌡️ Fractional distillation uses a fractionating column filled with glass rods to provide a high surface area for vapors to condense.
  • 📏 The fractionating column is taller, resulting in a temperature gradient from the bottom to the top, which is cooler.
  • 🔥 Methanol, with the lowest boiling point, is separated first by heating the mixture to around 65 degrees Celsius.
  • 🌡️ Ethanol is then separated by raising the temperature to approximately 78 degrees Celsius, leaving behind propanol.
  • 📝 The process can be repeated for each component, ensuring the purity of each liquid collected in the beaker.
Q & A
  • What is the purpose of simple distillation?

    -Simple distillation is used for separating a liquid from a solution, such as obtaining pure water from seawater.

  • What is the primary equipment used in simple distillation?

    -The primary equipment includes a flask containing the solution, a bung to seal the flask, a thermometer, a condenser with a water jacket, a beaker to collect the liquid, and a heating device like a Bunsen burner.

  • How does the condenser work in simple distillation?

    -The condenser works by having a main pipe surrounded by a water jacket. Cold water continuously flows through the jacket, cooling the vapor and causing it to condense back into liquid form.

  • What is the limitation of simple distillation when dealing with liquids with similar boiling points?

    -Simple distillation cannot effectively separate liquids with similar boiling points because more than one liquid will evaporate at the same time, preventing the separation into pure substances.

  • What technique is used to separate mixtures of liquids with similar boiling points?

    -Fractional distillation is used to separate mixtures of liquids with similar boiling points.

  • What is the key feature of a fractionating column in fractional distillation?

    -The fractionating column is full of little glass rods that provide a high surface area and is taller, resulting in a temperature gradient from the bottom to the top.

  • How does the fractionating column help in separating liquids with similar boiling points?

    -The fractionating column allows vapors to rise and cool as they come into contact with the glass rods. Liquids with lower boiling points evaporate first and condense, while those with higher boiling points condense back into the flask.

  • What is the process for separating methanol, ethanol, and propanol using fractional distillation?

    -First, heat the mixture to around 65 degrees Celsius to evaporate methanol. Then, raise the temperature to around 78 degrees Celsius to evaporate ethanol. Finally, increase the temperature again to remove propanol.

  • Why are the liquids shown as green in the video?

    -The liquids are shown as green in the video to make it easier to follow along, even though in real life they would be colorless.

  • How does the temperature control in fractional distillation help in separating specific liquids?

    -By controlling the temperature, only the liquid with the boiling point closest to the set temperature will evaporate and be separated, while others will condense back due to the cooler environment in the fractionating column.

  • What is the final step in the fractional distillation process after separating ethanol?

    -The final step is to raise the temperature again to boil off the remaining propanol, ensuring that only pure propanol is left in the flask.

Outlines
00:00
🔬 Simple Distillation Process

This paragraph introduces simple distillation, a method used to separate a liquid from a mixture, such as obtaining pure water from seawater. The equipment setup includes a flask containing the mixture, sealed with a bung to prevent gas escape, a thermometer to monitor temperature, a condenser with a water jacket for cooling vapors, and a beaker to collect the distillate. The process involves heating the mixture until the desired liquid evaporates, then cooling it in the condenser and collecting the condensed liquid. However, this method is ineffective for separating liquids with similar boiling points, such as methanol, ethanol, and propanol, which necessitates the use of fractional distillation.

05:04
🌡️ Fractional Distillation for Complex Mixtures

The second paragraph delves into fractional distillation, a technique for separating mixtures of liquids with similar boiling points. The equipment is similar to simple distillation but includes a fractionating column filled with glass rods to provide a large surface area and a temperature gradient from bottom to top. The process is illustrated using methanol, ethanol, and propanol, which are heated in stages to selectively evaporate and condense each component. Methanol, with the lowest boiling point, is first evaporated and collected, followed by ethanol at a higher temperature. The remaining propanol can be assumed to be pure or further heated to ensure purity. This method effectively separates components of complex mixtures.

Mindmap
Temperature Gradient
High Surface Area
Impurities Falling Back
Vapor Rising and Condensation
Heating to Specific Temperatures
Fractionating Column
Collection
Vapor Condensation
Heating Mixture
Heating Device
Beaker
Condenser
Thermometer
Flask
Color Coding
Advantages
Process
Equipment
Purpose
Limitation
Process
Equipment
Purpose
Educational Value
Visual Representation
Fractional Distillation
Simple Distillation
Distillation Techniques
Alert
Keywords
💡Distillation
Distillation is a process used to separate mixtures of liquids with different boiling points. It is the core technique discussed in the video, with two types being highlighted: simple and fractional distillation. The process is essential for understanding the theme of separating components of a liquid mixture, such as purifying water from seawater or separating alcohols with similar boiling points.
💡Simple Distillation
Simple distillation is a method used to separate a pure liquid from a solution, exemplified in the script by purifying water from seawater. It involves heating the mixture until the desired liquid evaporates, then condensing the vapor back into a liquid form and collecting it. This concept is foundational to the video's theme, illustrating the basic principles of liquid separation.
💡Fractional Distillation
Fractional distillation is a technique used for separating mixtures of liquids with similar boiling points, such as methanol, ethanol, and propanol. It is a more complex process than simple distillation, involving a fractionating column with glass rods to provide a high surface area for vapors to condense and separate. This keyword is crucial to the video's message, as it shows an advanced method for liquid separation.
💡Boiling Point
The boiling point is the temperature at which a liquid turns into vapor. In the context of the video, different boiling points are what allow for the separation of liquids during distillation. Methanol, ethanol, and propanol are used as examples to illustrate the need for fractional distillation when dealing with liquids with similar boiling points.
💡Flask
A flask is a type of container used in distillation to hold the liquid mixture. In the video script, the flask is described as being sealed at the top with a bung and containing a thermometer to measure the temperature of the mixture. It is central to the setup of both simple and fractional distillation processes.
💡Condenser
A condenser is a device used to cool and condense vapors back into a liquid form. The script describes a condenser with a main pipe surrounded by a water jacket, which is cooled by a continuous flow of cold water. The condenser is a key component in the distillation setup, facilitating the collection of the purified liquid.
💡Beaker
A beaker is a container used to collect the condensed liquid after distillation. In the video script, the beaker is placed beneath the condenser to capture the purified liquid, such as distilled water from seawater or separated alcohols in fractional distillation.
💡Bunsen Burner
A Bunsen burner is a heating device mentioned in the script for use under the flask to heat the liquid mixture during distillation. It is essential for initiating the evaporation process, which is the first step in both simple and fractional distillation.
💡Fractionating Column
A fractionating column is a key component of the fractional distillation setup. It is filled with glass rods to provide a large surface area for vapors to condense and is taller than it is wide, creating a temperature gradient from top to bottom. This allows for the separation of liquids with similar boiling points by condensing them at different heights within the column.
💡Methanol
Methanol is an alcohol with a low boiling point, used in the script as an example of a liquid that can be separated using fractional distillation. The video describes the process of heating a mixture containing methanol to evaporate it first, then condensing and collecting it separately.
💡Ethanol
Ethanol is another alcohol with a slightly higher boiling point than methanol. In the context of the video, ethanol is used to demonstrate the separation process in fractional distillation, where it is evaporated after the methanol and collected separately by adjusting the temperature.
💡Propanol
Propanol, with a boiling point higher than ethanol, is mentioned in the script to illustrate the complexity of separating mixtures with similar boiling points. It is the last liquid to be separated in the fractional distillation example provided in the video.
Highlights

Introduction to two types of distillation for separating mixtures containing liquids.

Simple distillation is used for separating a liquid from a solution, such as pure water from seawater.

Equipment for simple distillation includes a flask, thermometer, condenser, beaker, and heating device.

Process of heating the mixture to evaporate the desired liquid, which then condenses in the condenser.

Use of a fractionating column in fractional distillation for separating liquids with similar boiling points.

Fractional distillation equipment is similar to simple distillation but includes a fractionating column.

The fractionating column is filled with glass rods to provide a high surface area for condensation.

Temperature gradient in the fractionating column, cooler at the top than at the bottom.

Example of separating methanol, ethanol, and propanol using fractional distillation.

Heating the mixture to 65 degrees to evaporate methanol first.

Ethanol and propanol may also evaporate but will condense back into the flask upon contact with cooler glass rods.

Repeating the process for ethanol by raising the temperature to 78 degrees Celsius.

Assumption that what remains in the flask after evaporating ethanol is pure propanol.

Option to raise the temperature again to ensure all propanol is boiled off for purity.

Conclusion of the video with an invitation for feedback in the comments.

Anticipation of the next video in the series.

Transcripts
00:04

in today's video we're going to look at

00:06

the two types of distillation that we

00:08

can use to separate out mixtures that

00:11

contain

00:14

liquids let's start with simple

00:17

distillation

00:18

which is used for separating out a

00:20

liquid from a solution

00:23

for example we could use simple

00:25

distillation to separate pure water from

00:28

seawater

00:31

before we cover how it works though we

00:33

need to be familiar with the equipment

00:37

first we have a flask

00:39

that contains the solution or the liquid

00:42

mixture that we're trying to separate

00:44

and the flask is sealed at the top with

00:46

a bung so that no gas can escape

00:50

we then put a thermometer through the

00:51

bung so that we can measure the

00:53

temperature inside the flask

00:57

next we have our condenser

00:59

which consists of a main pipe surrounded

01:01

by a water jacket which contains a

01:03

stream of continually flowing cold water

01:07

with the water being fed into the water

01:08

jacket at the bottom

01:10

and coming out at the top

01:13

then beneath the end of our condenser

01:15

we'll have some sort of beaker to

01:17

capture our pure liquid

01:20

and finally we're going to need some

01:22

sort of heating device like a bunsen

01:23

burner which we place under the flask

01:30

our first step is to heat up the mixture

01:33

so that the liquid that we want

01:35

evaporates

01:37

as it rises to the top of the flask the

01:39

pressure will force it down the

01:40

condenser

01:42

and because we're pumping cold water

01:44

through the water jacket

01:46

the vapor will cool and condense into

01:48

liquid form

01:50

which will then run down the pipe and

01:52

collect in the beaker

02:00

so in our case as we heat the seawater

02:03

we'll get more and more pure distilled

02:05

water

02:06

until eventually all we have left in the

02:08

flask is salt

02:14

now imagine instead that we were trying

02:16

this technique with a different mixture

02:19

one containing some different liquids

02:21

like methanol ethanol and propanol

02:27

because these liquids all have similar

02:29

boiling points

02:30

when we heat them more than one of them

02:32

will evaporate

02:33

and so they won't be separated into pure

02:36

substances

02:41

in this case we'd have to use a

02:43

different technique called fractional

02:45

distillation

02:46

which is the main technique used for

02:48

separating mixtures of liquids

02:52

the equipment for this is pretty similar

02:55

but instead of the gas passing straight

02:57

from the flask into the condenser

03:01

the vapors have to first pass through a

03:03

fractionating column

03:05

which has two key features

03:08

one is that it's full of little glass

03:10

rods which provide a really high surface

03:13

area

03:15

and the other is that because the colon

03:17

is so tall

03:19

it's actually cooler at the top than it

03:21

is at the bottom

03:24

to understand why this is important

03:26

let's imagine that we were trying to

03:28

separate those three liquids that we

03:29

mentioned before

03:31

methanol

03:32

ethanol and propanol

03:35

which all have similar boiling points

03:38

although you don't need to remember them

03:40

and before we continue just be aware

03:42

that in real life these would all be

03:44

colorless not green

03:46

we're just showing them as green to make

03:48

it easier to follow along

03:54

now because methanol has the lowest

03:56

boiling point we'd heat the mixture to

03:58

around 65 degrees first

04:02

this would cause the methanol to

04:03

evaporate and then rise up the

04:06

fractionating column

04:08

it would then pass into the condenser

04:10

and condense into liquid methanol

04:13

which would then collect in our beaker

04:17

however just by chance some of the

04:19

ethanol and maybe even propanol would

04:22

also evaporate

04:24

but as they rise up the fractionating

04:26

column and come into contact with all of

04:28

those glass rods which are much cooler

04:30

than their boiling point

04:32

they'd condense back into liquid form

04:34

and fall back into the flask

04:39

this means that the only liquid that

04:40

will get out the other side will be pure

04:42

methanol

04:46

the next step would be to do the same

04:47

thing all over again for ethanol by

04:50

raising the temperature to around 78

04:52

degrees celsius

04:53

which will allow us to evaporate off the

04:55

ethanol

05:03

at this point all that should be left is

05:05

the propanol

05:07

so we could just assume that what we

05:09

have in the flask is pure propanol

05:12

or we could raise the temperature again

05:14

to boil off the propanol just to make

05:16

sure

05:21

anyway that's all for today so hope you

05:24

enjoyed this video if you did then

05:26

please let us know down in the comments

05:28

and we'll see you next time