Separation

Question 1

What is a pure substance?

Answer 1

A substance that only contains one element or compound

Question 2

What is an impure substance?

Answer 2

A substance that contains one or more elements or compounds

Question 3

What is the everyday definition for pure?

Answer 3

A substance that has not been processed or changed

Question 4

How can we use melting points to differentiate between pure and impure substances?

Answer 4

• The melting point is less than that of the pure substance
• Often melts over a range of temperatures

Question 5

What is filtration?

Answer 5

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.

Question 6

What is Crystallization?

Answer 6

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

Question 7

Why do crystals form?

Answer 7

Crystals form because as the liquid evaporates, the solid will get more concentrated and form crystals

Question 8

What is a mixture?

Answer 8

A mixture is made from different substances that are not chemically joined.

Question 9

What is a compound?

Answer 9

A compound is a substance formed when two or more different types of atoms are chemically bonded together.

Question 10

What is a molecule?

Answer 10

2 or more atoms, held together by chemical bonds

Question 11

What is an element?

Answer 11

An element is a pure substance that consists of only one type of atom and cannot be broken down into simpler substances.

Question 12

What two things does a successful chromotography need?

Answer 12

A mobile phase and a stationary phase

Question 13

What is a phase?

Answer 13

Substance that is a solid, liquid or gas.

Question 14

In paper chromotography, what is the mobile and the stationary phase?

Answer 14

Mobile phase - Solvent (often water)
Stationary Phase - Paper

Question 15

What does the solubility of a substance mean in chromotography?

Answer 15

TThe more soluble a substance is, the further it will travel.

Question 16

What do we call the final results?

Answer 16

A chromotogram

Question 17

What is the first step of chromatography (paper)

Answer 17

Take a piece of paper and draw a line near the bottom of it with a pencil

Question 18

What is the second step of chromatography?

Answer 18

Next, we add a sample of ink to the pencil line

Question 19

What is the third step of chromatography?

Answer 19

Then we fill a beaker with a shallow amount of solvent underneath the baseline

Question 20

What is the fourth step of chromatography?

Answer 20

Place the paper into the solvent

Question 21

What is the fifth step of chromatography?

Answer 21

Put a lid onto the beaker to stop it evaporating.

Question 22

How does chromatography work?

Answer 22

A mobile phase (solvent) carries the components of the mixture through the stationary phase

Question 23

The further a component moves, the more it is _______ in the solvent?

Answer 23

Soluble

Question 24

Chemicals that are more soluble spend ____ time in the mobile phase?

Answer 24

More

Question 25

What does Rf stand for?

Answer 25

Retention Factor

Question 26

How do you carry out crystalisation?

Answer 26

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

Question 27

Why do crystals form when the solution is left to cool?

Answer 27

The solubility of the solid decreases.

Question 28

What is one thing you need to carry out distillation?

Answer 28

Your mixture's components must have different boiling points

Question 29

How do you carry out distillation?

Answer 29

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

Question 30

Equipment needed for crystallisation?

Answer 30

Water Bath, Evaporating basin. If filtering, Filter paper and filter funnel and beaker, or if evaporating, bunsen burner

Question 31

What are the two types of distillation?

Answer 31

Fractional and simple

Question 32

Equipment needed for distillation?

Answer 32

Flask, column, Liebig condenser, beaker, Bunsen burner.

Question 33

Equipment needed for filtration?

Answer 33

Filter paper, filter funnel, beaker

Question 34

How does filtration work?

Answer 34

Filter paper has microscopic holes that can let one substance through, but not the other

Question 35

How do you carry out distillation?

Answer 35

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.

Question 36

How do you carry out chromatography?

Answer 36

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.

Question 37

What do we use to put a sample of ink on the baseline?

Answer 37

Capiliary tube

Question 38

How do you calculate the Rf value?

Answer 38

Total distance travelled by component / Total distance travelled by solvent

Question 39

What can the Rf value never be more than?

Answer 39

1

Question 40

What is a solute?

Answer 40

Something that dissolves in water.

Question 41

What is a solvent?

Answer 41

Something that dissolves other materials

Question 42

What is faster, Crystallization or evaporation?

Answer 42

Evaporation

Question 43

What do we often use to heat the solution with when we are carrying out crystallisation?

Answer 43

A waterbath

Question 44

What is the difference between fractional distillation and simple distillation?

Answer 44

Simple distillation cannot seperate liquids with similar boiling points

Question 45

What is the condenser in distillation know as?

Answer 45

Liebig condensor

Question 46

What technique would we use to seperate ethanol and water?

Answer 46

Distillation

Question 47

What technique would we use to separate sand and water?

Answer 47

Filtration

Question 48

What technique would we use to separate salt and water?

Answer 48

Crystallisation

Question 49

What technique would we use to separate crude oil

Answer 49

Fractional distillation

Question 50

What is the plate in TLC chromatography coated with

Answer 50

Silica gel

Question 51

What solvent is used in paper chromatography?

Answer 51

Water

Question 52

What are the three types of chromotography?

Answer 52

Gas chromatography, TLC and paper

Question 53

If there is an impure substance, what would we see on the chromatogram?

Answer 53

Multiple spots

Question 54

What would be the result of a pure substance being tested using chromatography?

Answer 54

Produces a single spot

Question 55

What is an inert substance?

Answer 55

Non reactive substances used in TLC chromatography

Question 56

Method to test purity of a solid

Answer 56

Melt the solid and check the temperature it melted at, and then compare it against the value known in the data books

Question 57

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?

Answer 57

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.

Question 58

What is the change is melting point/ boiling point from pure and impure substances

Answer 58

The melting points and boiling points are varied Boiling points are higher Melting points are lower

Question 59

Why can water and ethanol be seperated through distillation?

Answer 59

They have different boiling points

Question 60

Why must the baseline not be drawn in pen?

Answer 60

The pen ink could dissolve in the solvent

Question 61

What is a concentrated solution?

Answer 61

Solution that has large amount of solvent relative to the amount that could dissolve

Question 62

What is a dilute solution?

Answer 62

Solution when there is a relatively small amount of solute dissolved in a given solvent.

Question 63

What is a saturated solution?

Answer 63

Solution that cannot dissolve any more solute at a given temperature, any extra solute added will remain undissolved.

Question 64

What does a larger Rf value suggest?

Answer 64

The substance is more soluble than others

Question 65

What is a Bung?

Answer 65

Rubber stopper to stop gas escaping test tubes?

Question 66

When carrying out distillation, what do you put through a bung?

Answer 66

A thermometer

Question 67

What does distillation seperate?

Answer 67

A liquid from a solution

Question 68

In distillation, what is the condensor made up of?

Answer 68

Main pipe, water jacket. The water jacket has a stream of continually flowing cold water to cool the gas.

Question 69

In the water jacket, where does the water enter and exit from?

Answer 69

Enters from the bottom and exits form the top.