Topic 4: Separation Techniques Flashcards
Give three examples of materials which are mixtures?
Tea, mineral water, milk
Give 4 examples of pure materials?
Sugar, ethanol, vinegar, de-ionised water.
What is a solute?
A solid that will dissolve in a liquid solvent
What is a solvent
A liquid which dissolves a solid solute
What is a solution?
A mixture produced when a solute dissolves in a solvent
What will the method of separation depend on?
The method of separation used will depend on the nature of both A + B.
What do we mean by nature?
By nature we mean the properties of the substance. For example, is it a liquid or a solid? Does a solid dissolve in a liquid? (Then it is said to be SOLUBLE). Does a solid not dissolve in a liquid? (Then it is said to be insoluble). Liquids that are easily evaporated have low boiling points. Liquids that are difficult to evaporate have high boiling points.
What is evaporation?
A separation technique changing a liquid to a gas
How do we carry out evaporation?
Place a solution in an evaporating basin and heat over a Bunsen Burner
Give examples of mixtures that can be separated by evaporation?
Salt water, sugar - Water solutions
Draw and label a diagram of simple evaporation?
Look at book
How could yo improve the simple method of evaporation and why does it improve it?
Place a beaker of water under the evaporating dish to gently evaporate the water and prevent the evaporating basin spitting out
Which mixtures are separated by filtration?
Insoluble solids and solvents
How do we carry out filtration?
We use filter paper, conical flask, a filter funnel, a beaker (with liquid in it) and pour the liquid through the funnel
Give examples of mixtures that can be separated by filtration?
Sand and water
How do you fold a piece of filter paper?
Fold filter paper in half. Fold into quarters with top section smaller than bottom. Tear off corner of smaller section. Open cone
Draw and label filtration diagram?
Look at book
If small particles of an insoluble substance is put into a liquid what is formed?
Solution
When a suspension is filtered, what are left in the filter paper?
Insoluble particles. They cannot go through the filter paper
What is sand in water?
Insoluble
What is formed when the sand is stirred with water?
A suspension
How can sand and water be separated?
Filtration
On filtering, what is the sand and water?
On filtering, the sand is the solid and the water is the liquid
What is the chemical name for table salt?
Sodium chloride
What is rock salt?
A mixture of salt, sand and other impurities
Name two methods that are used to extract salt so it can be sold in the supermarket?
Solution mining to obtain rock salt or evaporation to obtain sea salt
Where in Northern Ireland is salt currently extracted from the ground?
Carrickfergus
What is this salt used for?
Gritting the roads
What was salt used for before there were refrigerators?
It was used as a preservative
What is the method for separating rock salt?
- Take a 10g sample (approximately) of rock salt and put it in the pestle and mortar.
- Mix the salt with just enough water.
- Slowly filter the suspension into a conical flask.
- Transfer the solution into evaporation basin and heat it over Bunsen.
- Let it evaporate until you have white crystals.
List the apparatus you will use to separate rock salt and include a diagram?
Look at book
What is the appearance of a sample and what is the name of the substance?
White crystals
Rock salt
What is the appearance of a solute and what is the name of the substance?
White salt
Salt
What is the appearance of a residue and what is the name of the substance?
Brown powder
Sand
Why is salt not an element?
Salt is not an element; it is sodium chloride which is a compound
Why was salt very important in the past?
Salt was very important in the past as Romans exploited the stuff and Domesday mentions ‘salt-houses’. Also it was used to cure some illnesses like gout, rheumatism and even insomnia!
What is brine?
Brine is salty water / a salt solution
Why was brine pumped?
So the salt water could reach the ground surface. The water could then be evaporated, leaving the salt behind.
Why would grind being pumped cause subsidence?
Removing some of the solid salt would create holes underground so land could subside
How would salt be obtained from brine?
Evaporation
Why is salt put on roads?
It lowers the melting point of ice so at 0°C the ice exists as a liquid. Hence the ice has melted.
How can they gain salt hot countries where no rock salt occurs?
They can evaporate it from sea water. This is called sea salt
What is filtration used to separate?
Used to separate an insoluble substance from a solution e.g.sand from water
What is evaporation used to separate?
Used to separate a soluble substance from s solution e.g. Salt from salt solution
Fill in the missing words:
Distillation can be use to obtain a _________ sample of the solvent from a _________________. The mixture is heated so that it __________. A few anti-bumping granules are placed in the mixture to make it boil ____________. Distillation makes use of the __________________
in the substances’ boiling points. The distillate distill over because it has the _____________ boiling point. Simple distillation is the best method for separating a liquid from a soluble __________ since their boiling points are far apart. For example distillation can be used to obtain pure ___________ from a salt solution.
Pure, solution, boils, gently, differences, lower, solid, water
Draw and label a simple distillation diagram?
Look at book
What is the method for obtaining a sample of water from copper sulfate solution using distillation?
Place approximately 25cm3 of copper sulfate solution in a conical flask on top of a gauze on a tripod. Clamp the neck of the conical flask in place. Using test tube holders, hold a test tube around the delivery tube. Heat the conical flask strongly and collect the water produced in e test tube. Stop heating as soon as steam is seen escaping from the test tube and set the test tube in a test rack.
Give two ways in which we could confirm that the liquid produced is water?
If it has a boiling point of 100°C and freezes at 0°C.
If it is a pure clear substance.
Why did some of the water in the solution turn into steam in the conical flask?
This happened because we boiled it at 100°C
What happens to the steam in the delivery tube? Why does this happen?
The steam gets pushed through the delivery tube and into the boiling tube creating water. This happens because the steam has nowhere else to go as more and more comes out.
Why did the apparatus stop working after a few minutes?
The delivery tube became too warm, this meant that the steam would not condense because there was nothing to cool it down.
How could the apparatus be improved so that this does not happen?
If there was cold water constantly circulating it
Draw and label a diagram of improved distillation apparatus?
Look at book
If you were stranded on a desert island and desperately needed pure drinking water how might you obtain it from the sea water?
- Dig a hole in the sand where you will get lots of sun.
- Line it with a big palm frond that will hold a puddle of water.
- Go find a sheet of transparent plastic etc.
- Put the plastic over the hole, and then set a rock right in the middle so that it bows down slightly.
- Either try to put in another palm frond, or go off and find a mug that washed up on shore etc.
- Put the mug directly underneath the rock.
- Put water in the palm frond.
- The sun will cause the water to evaporate, and when it rises, it will hit the plastic, then run down to where the rock is sitting and drop off as fresh water into the mug you find, because evaporating water is always fresh water.
What is fractional distillation used to separate?
Two miscible liquids
Explain how the fractional distillation apparatus works?
The apparatus for fractional distillation, is the same as the apparatus for simple distillation except the vapor must travel of a long fractionating column before reaching the condenser. The fractionating column is filled with small beads off class which ensures that the substances are completely separated.
Name the two liquids that were separated by fractional distillation?
Ethanol and water
What difference did ethanol and water have in their properties which was used to separate the liquids?
They have different boiling points
What is the boiling point of ethanol?
78°C
Which of the two liquids distills over first?
Ethanol
Why does ethanol distill over first?
As the condensation goes farther up, the temperature decreases making it only possible for the ethanol to evaporate.
I was the first liquid distills over, what will the temperature shown on the thermometer be equal to?
78°C, the boiling point of ethanol
Draw and label a diagram of the fractional distillation apparatus?
Look at book
How do you separate to miscible double liquids?
Fractional distillation
What do you call two liquid that will not mix together?
Insoluble
How can insoluble mixtures be separated?
Using a separation funnel
How else is the method of using a separation funnel carried out?
This method of separation is carried all eat on a larger scale in oil storage tanks. Here the oil company must employ someone to drain water from the bottom off the storage tank. Oil is less dense than water so it floats on the top.
What is the method of using a separation funnel?
- Collect a separating funnel and a beaker from the tray at the side of the lab. If the separating funnel does not contain the oil and water mixture, your teacher will give you some.
- Separate the water (i.e.the red or blue liquid) from the oil (i.e. the cloudy liquid) by opening the top and running the water into the beaker. It is essential to remove the separating funnels stopper before doing this.
- Pour the water back into the separating funnel and let someone else in the group have a go. Keep the oil in the separating funnel at all times.
- When you have finished, put the stopper back on the separating funnel containing both oil and water.
- Return both the separating funnel and beaker to the tray.
Name the five products that come from oil?
Crayons, plastics, heating oil, jet fuel, tires
What does the term crude oil stand for?
Crude oil is the term for “unprocessed” oil, the stuff that comes out of the ground.
How is crude oil separated at an oil refinery?
The oil refining process starts with a fractional distillation column.
Name the eight products that come from the fractional distillation column?
Petroleum gas, Naphtha or Ligroin, Gasoline, Kerosene, Gas oil or diesel distillate, Lubricating oil, Heavy gas or fuel, residuals.
What is kerosene used for?
Jet engines and tractors; starting material for making other products.
What are residuals used for?
Cake, asphalt, tar, waxes; starting material for making other products
Can you suggest another type of industry that carries out distillation?
Alcohol factories
What is ink a mixture of?
Different dyes
What is chromatography?
Chromatography is the technique that is used to separate the dyes found in a mixture
How is a chromatogram prepared?
A chromatogram is prepared using special chromatography filter paper. The chromatogram is then placed in a beaker of water and the water travels up the chromatography paper. As this water travels along the chromatography paper different dyes become dissolved in the water. These dyes will then come out off the solution at different rates as the water moves up the paper. The dyes are there for separated out.
Draw and label a diagram of chromatography?
Look at book
Name three areas of chemistry that use chromatography?
Forensic chemistry
Environmental chemistry
Pharmaceutical chemistry
What is the main advantage of carrying out chromatography?
Only tiny samples are required
How do you prepare chromatography paper?
- You will be given a piece of chromatography paper 5 cm long.
- Draw a pencil line 1 cm up from the base of the paper.
- You will be given four inks.
- Make for pencil marks equally spaced across the paper and label (also using a pencil) A (sample), B (Mr Brown), C (Mr Green, D (Mr Black).
- Dip a clean glass capillary tube into each ink and put a small spot on the paper.
- Add three droppers cell off water to a 100 cm³ beaker.
- Carefully lower the paper into the beaker. Make sure that the water doesn’t splash up above the pencil line.
- With as the water absorbs up the paper, carrying the dyes with it.
- When the water gets near the top, take the paper out and let it dry.
- Find out the rest of your information that you need to know.
What is the type of mixture separated and give an example for the separation technique of filtration?
Insoluble solid suspension from a liquid
Sand and water
What is the type of mixture separated and give an example for the separation technique of evaporation ?
Soluble solid from a solution
E.g. Separate salt from a salt-water solution
What is the type of mixture separated and give an example for the separation technique of distillation?
Solvent from solution
E.g. Water from a salt water solution
What is the type of mixture separated and give an example for the separation technique of fractional distillation?
A mixture of liquids
E.g. Crude oil to gain petrol
What is the type of mixture separated and give an example for the separation technique of separating funnel?
Oil from water
E.g. Oil and water
What is the type of mixture separated and give an example for the separation technique of chromatography?
A mixture of dyes
Food colouring
What method of separation is used for oil and water?
Using a separating funnel
What method of separation is used for iron sulfur?
Using distillation
Draw filter paper?
Look at book
Draw a filter funnel?
Look at book
Draw a conical flask?
Look at book
What is the general name for the solid which sits on the filter paper?
Insoluble solid residue
What is the general name for the liquid which drops into the conical flask?
Filtration
Name one mixture which could be separated by filtration?
Sand stirred with water
Name the separation technique that would provide the best separation of a mixture of water and ethanol?
Distillation
Give examples of two immiscible liquids?
Water and oil
Plan a practical method for the separation of a mixture of sand and water?
Filtration
Draw and label a diagram of filtration?
Look at book
Draw a labeled diagram to show the apparatus you would use in order to separate out salt from salty water.mthe method you should use is separation?
Look at book
What name is given to the method of separating dyes?
Chromatography
