Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chemistry > 2 - Methods of purifying & separating substances > Flashcards

2 - Methods of purifying & separating substances Flashcards

(59 cards)

Start Studying
1
Q

What is a pure substance?

A

A single substance with a fixed composition that does not have anything mixed with it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the composition of a pure substance:

A
  • Cannot be changed
  • Is the same in all parts of the substance

E.g Pure gold only contains gold atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is an Element?

A

A simple substance made up of only one type of atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a Compound?

A

A substance that can be split into simpler substances because it contains the atoms of two or more elements joined together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a Mixture?

A

A mixture containing two or more different substances that are not joined together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How would a heating curve look like for a mixture?

A

Melts over a range of temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How would a heating curve look like for a pure substance?

A

Has a sharp melting point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is an insoluble substance?

A

A substance that cannot be dissolved in a certain liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Give me some examples of filtration in day to day life?

A
  • Cars
  • Vacuum cleaners
  • Air-conditioning systems
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a Solvent?

A

Describes the liquid in which a substance dissolves to make a solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a Solute?

A

Describes a substance that dissolves in a liquid to make a solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a Solution?

A

A mixture formed by a solvent and a solute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is Crystallisation?

A

Separating the solute from a solution by evaporating the solvent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does crystallisation form?

A

Solid crystals of various sizes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How would you get the crystals to be larger & form an ordered pattern in crystallisation?

A
  • Put the solution in an evaporating basin
  • Warm the solution by placing the evaporating basin over a boiling water bath
  • Stop heating before all the solvent has evaporated

After the remaining solution has cooled down, pour the excess liquid away (or filter it). Dry the crystals using a warm oven or in air.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens if the crystals in crystallisation form more slowly?

A

The particles have longer to form an ordered pattern & will make larger crystals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a Saturated solution?

A

Contains the maximum amount of solute that can dissolve in that amount of solvent at that temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How would you filter a solution?

A
  • A filter funnel is lined with filter paper that has fine holes in it
    —> The solvent & solute(s) pass through the fine holes to form filtrate
  • Some insoluble substances cannot fit through the holes and leave a residue in the filter paper
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How would you do crystallisation after you’ve filtered your solution?

A

A Bunsen burner is used to evaporate the filtrate but don’t overheat the solution once it is saturated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why must you take care to not overheat the solution once it’s saturated in crystallisation?

A
  • Hot crystals may spit out
  • Further heating may cause crystals to change chemically
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a Hazard?

A

Something that could cause harm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a Risk?

A

The chance of a hazard causing harm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is a risk assessment?

A
  • The hazards of doing an experiment are identified
  • Then, ways of reducing the risk of a hazard causing harm is considered
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How can the risks from spitting be reduced during crystallisation?

Study These Flashcards
A
  • Wearing eye protection
  • Removing the Bunsen burner before the solution is completely dry
  • Using steam to heat the evaporating basin gently
25
What is **Chromatography**?
A technique of separating the components of a mixture | E.g. Different food colouring agents
26
What is the **Stationary phase** in chromatography?
The surface through which the solvent and dissolved substances move in chromatography
27
What is the **Mobile phase** in paper chromatography?
When the solvent moves along the paper carrying dissolved samples with it
28
What is a **Chromatogram**?
The piece of paper showing the results of chromatography
29
Explain what is *paper chromatography*:
The separation of mixtures of soluble substances by running a solvent (mobile phase) through the mixture on the paper (the paper contains the stationary phase) ---> This causes the substances to move at different rates over the paper
30
What is the **Rf Value**? | And what do they range from?
| Rf values range from 0 - 1
31
What is *paper chromatography* used for:
* Distinguishing pure & impure substances * Identifying substances by calculating their Rf values * Identifying substances by comparing the pattern on the chromatogram with the patterns formed by known substances
32
How can you 'distinguishing pure & impure substances' in a paper chromatogram?
Pure substance = one spot Impure substance/mixture = two or more spots | *On the chromatogram
33
How can you 'Identify substances by comparison with known substances' in a paper chromatogram?
* They produce the same number of spots and match in colour. t * The spots have the same R f value
34
How can you 'Identify substances by calculation and use of Rf values' in a paper chromatogram?
Substances which are the same will have the same Rf value
35
What is **Distillation**?
The process of separating a liquid from a mixture by evaporating the liquid and then condensing it (so it can be collected)
36
What is **Simple distillation**?
Separation method used to separate a solvent from a solution.
37
When does *Simple distillation* work?
When the dissolved solute has a much higher boiling point than the solvent
38
How does *Simple distillation* work?
When the solution is heated, solvent vapour evaporates from the solution The gas moves away and is cooled and condensed. The remaining solution becomes more concentrated in solute as the amount of solvent in it ⬇️.
39
Which way does water go in and out in the condenser?
40
What is a **Still**?
A piece of apparatus used to carry out distillation or fractional distillation
41
Why is this method of simple distillation NOT efficient?
Much of the vapour is lost
42
What is **Fractional distillation**?
A method of separating a mixture of liquids with different boilng points into individual components (fractions)
43
What are some of the uses of *Fractional distillation*?
* To separate the different products in crude oil * To make alcoholic drinks (e.g. Whiskey, Vodka) * To separate the gases in the air, after the air has been cooled & turned to a liquid at -200 degrees Celsius
44
Is the fractions in fractional distillation pure substances?
It can be pure or a mixture
45
Why is this method of fractional distillation efficient?
The condenser keeps the tube cool, so that almost all of the vapour condenses turn into a liquid
46
What is **desalination**?
A process that produces fresh drinking water by separating the water from the salts in salty water
47
What does **potable** mean?
Safe to drink
48
Using which process can sea water be made potable?
Simple distillation
49
When is purifying sea water by distillation carried out on a large scale?
* Where energy resources are cheap / plentiful * An abundant supply of sea water
50
What is **Chemical analysis**?
Using chemical reactions or sensitive machines to identify & measure the substances in a sample
51
What will happen if the water used in *Chemical analysis* contains dissolved salts?
Incorrect results will be obtained
52
What will happen if you use tap water in *Chemical analysis* ?
Tap water contains small amounts of dissolved salts ---> May react to form unexpected cloudy precipitates May hide the correct result of the analysis
53
What is an **Aquifer**?
Underground rocks containing groundwater
54
What does *fresh water* from reservoirs, lakes, rivers or aquifers contain? | And give an example of each point
* Objects (e.g. Leaves, Twigs) * Small insoluble particles (e.g. Grit, Salt) * Soluble substances (e.g. salts, pesticides & fertilisers) * Bacteria / other microorganisms that may be harmful to health
55
What is **Chlorination**?
The process of adding Chlorine to a substance (often water)
56
What is **Sedimentation**?
The process in which rock grains & insoluble substances sink to the bottom of a liquid
57
What steps are needed to deal with impurities in *fresh water* so it can be made potable?
* Screening using a sieve * Sedimentation * Filtration (using tanks containing beds of sand & gravel) * Chlorination (chlorine kills microorganisms in the treated water)
58
# Core practical: Investigating inks How would you use **simple distillation** to separate a sample of the **solvent from the ink**?
1) Set up apparatus 2) Heat the flask of ink using a Bunsen burner. Make sure ink simmers gently and does not boil over delivery tube 3) Continue heating until you have collected enough distilled solvent 4) Note max temp obtained
59
# Core practical: Investigating inks How would you use **paper chromatography** to separate the *coloured substances* in samples of **ink**?
1) draw a pencil line on a chromatography paper (around 2cm from bottom) 2) Add a small spot of ink to pencil line 3) Add water to a container to a depth of about 1cm 4) Place paper in container (make sure its supported). Allow water to travel through paper 5) Take paper out before it reaches the top 6) Calculate the Rf value for each substance

Chemistry (29 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions