Separation Flashcards
What is a pure substance?
A substance that only contains one element or compound
What is an impure substance?
A substance that contains one or more elements or compounds
What is the everyday definition for pure?
A substance that has not been processed or changed
How can we use melting points to differentiate between pure and impure substances?
- The melting point is less than that of the pure substance
- Often melts over a range of temperatures
What is filtration?
A separation process that separates an insoluble solid and a liquid by using filter paper, a filter funnel and a beaker. Works because the filter paper has microscopic holes in it that allow water to pass through, however stop the larger solid from.
What is Crystallization?
Process of gradually heating the solution until crystals form, then cooling the solution to let even more crystals form, and then filtering out the crystals
Why do crystals form?
Crystals form because as the liquid evaporates, the solid will get more concentrated and form crystals
What is a mixture?
A mixture is made from different substances that are not chemically joined.
What is a compound?
A compound is a substance formed when two or more different types of atoms are chemically bonded together.
What is a molecule?
2 or more atoms, held together by chemical bonds
What is an element?
An element is a pure substance that consists of only one type of atom and cannot be broken down into simpler substances.
What two things does a successful chromotography need?
A mobile phase and a stationary phase
What is a phase?
Substance that is a solid, liquid or gas.
In paper chromotography, what is the mobile and the stationary phase?
Mobile phase - Solvent (often water)
Stationary Phase - Paper
What does the solubility of a substance mean in chromotography?
TThe more soluble a substance is, the further it will travel.
What do we call the final results?
A chromotogram
What is the first step of chromatography (paper)
Take a piece of paper and draw a line near the bottom of it with a pencil
What is the second step of chromatography?
Next, we add a sample of ink to the pencil line
What is the third step of chromatography?
Then we fill a beaker with a shallow amount of solvent underneath the baseline
What is the fourth step of chromatography?
Place the paper into the solvent
What is the fifth step of chromatography?
Put a lid onto the beaker to stop it evaporating.
How does chromatography work?
A mobile phase (solvent) carries the components of the mixture through the stationary phase
The further a component moves, the more it is _______ in the solvent?
Soluble
Chemicals that are more soluble spend ____ time in the mobile phase?
More
What does Rf stand for?
Retention Factor
How do you carry out crystalisation?
Slowly heat the solution, preferably in a water bath. Then, once you start to see crystals forming, take the evaporating basin out of the water bath and let it cool, allowing more crystals to form. Then, you can either evaporate the water or filter out the crystals. Then dry
Why do crystals form when the solution is left to cool?
The solubility of the solid decreases.
What is one thing you need to carry out distillation?
Your mixture’s components must have different boiling points
How do you carry out distillation?
Heat the flask with the solution until it evaporates. One of the liquids will evaporate and rise. Then pass this liquid through a condensor and condense it into a liquid, and then collect
Equipment needed for crystallisation?
Water Bath, Evaporating basin. If filtering, Filter paper and filter funnel and beaker, or if evaporating, bunsen burner
What are the two types of distillation?
Fractional and simple
Equipment needed for distillation?
Flask, column, Liebig condenser, beaker, Bunsen burner.
Equipment needed for filtration?
Filter paper, filter funnel, beaker
How does filtration work?
Filter paper has microscopic holes that can let one substance through, but not the other
How do you carry out distillation?
Heat the flask with the liquid in it. Then, as the liquid with the lowest boiling point evaporates, it will pass through the condenser as vapor and condense back into a liquid, where it will drip into a separate beaker.
How do you carry out chromatography?
First, get a pencil and draw a baseline near the bottom of the paper. Then you get a sample of ink and put it on the baseline. Then fill a beaker with a shallow amount of solvent, make sure that the baseline is not submerged in the solvent. Finally, put the paper in the beaker and put a lid on it.
What do we use to put a sample of ink on the baseline?
Capiliary tube
How do you calculate the Rf value?
Total distance travelled by component / Total distance travelled by solvent
What can the Rf value never be more than?
1
What is a solute?
Something that dissolves in water.
What is a solvent?
Something that dissolves other materials
What is faster, Crystallization or evaporation?
Evaporation
What do we often use to heat the solution with when we are carrying out crystallisation?
A waterbath
What is the difference between fractional distillation and simple distillation?
Simple distillation cannot seperate liquids with similar boiling points
What is the condenser in distillation know as?
Liebig condensor
What technique would we use to seperate ethanol and water?
Distillation
What technique would we use to separate sand and water?
Filtration
What technique would we use to separate salt and water?
Crystallisation
What technique would we use to separate crude oil
Fractional distillation
What is the plate in TLC chromatography coated with
Silica gel
What solvent is used in paper chromatography?
Water
What are the three types of chromotography?
Gas chromatography, TLC and paper
If there is an impure substance, what would we see on the chromatogram?
Multiple spots
What would be the result of a pure substance being tested using chromatography?
Produces a single spot
What is an inert substance?
Non reactive substances used in TLC chromatography
Method to test purity of a solid
Melt the solid and check the temperature it melted at, and then compare it against the value known in the data books
After testing it is found that the boiling point of distilled water is 100 degrees, while the boiling point or salt water is 105 degrees.
How can we use these results to explain why the salt water is not pure?
Salt water has higher boiling point than pure water. So, the prescence of salt imputities raises the boiling point of the water, showing us that this is an impure substance.
What is the change is melting point/ boiling point from pure and impure substances
The melting points and boiling points are varied
Boiling points are higher
Melting points are lower
Why can water and ethanol be seperated through distillation?
They have different boiling points
Why must the baseline not be drawn in pen?
The pen ink could dissolve in the solvent
What is a concentrated solution?
Solution that has large amount of solvent relative to the amount that could dissolve
What is a dilute solution?
Solution when there is a relatively small amount of solute dissolved in a given solvent.
What is a saturated solution?
Solution that cannot dissolve any more solute at a given temperature, any extra solute added will remain undissolved.
What does a larger Rf value suggest?
The substance is more soluble than others
What is a Bung?
Rubber stopper to stop gas escaping test tubes?
When carrying out distillation, what do you put through a bung?
A thermometer
What does distillation seperate?
A liquid from a solution
In distillation, what is the condensor made up of?
Main pipe, water jacket. The water jacket has a stream of continually flowing cold water to cool the gas.
In the water jacket, where does the water enter and exit from?
Enters from the bottom and exits form the top.
