Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chemistryyyy > C2.1- Purity And Seperating Mixtures > Flashcards

C2.1- Purity And Seperating Mixtures Flashcards

1
Q

What is the relative atomic mass (Ar)?

A

It is the mean mass of an atom compared to 1/12 the mass of a carbon-12 atom

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

What does a chemical formula tell you?

A

It tells you how many atoms of each element there are in a unit of a substance

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

What is the relative formula mass (Mr)

A

Relative formula mass is the mean mass of a unit of a substance compared to 1/12 the mass of a carbon-12 atom

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

What is the difference between relative formula mass and relative molecular mass

A

Relative formula mass refers to all substances that consist of 2 or more atoms. Relative molecular mass refers to substances that exist as molecules

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

What is an empirical formula?

A

An empirical formula shows the simplest whole number ratio for each element in a compound.

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

What does pure mean in every day life?

A

Natural Substances that have not been processed or changed

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

What is ‘pure’ in science

A

A substance that consists of one element or compound.

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

Are the atoms in alloys the same or different sizes

A

They are usually different sizes

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

What is an alloy?

A

A mixture of a metal with one or more other elements.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the melting point of a substance?

A

It is the temperature at which it changes from the solid state to the liquid state.

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

How can you tell if a substance is impure from its melting point.

A
  • the melting point of a pure substance is a single temperature
  • an impure substance melts over a range of temperatures and its melting point is less than that of a pure substance.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When you determine the melting point it is important to…

A
  • Heat the substance slowly

- Stir the substance as is melts

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

Heating a substance allows…

A

The temperature of the whole sample to increase

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

What does mixing a sample ensure

A

That the entire sample is the same temperature.

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

What is a solution?

A

A mixture formed when one substance dissolves in another.

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

What is a solute

A

The substance that dissolves in a solvent

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

What is a solvent

A

A substance that a solute dissolved in

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

What happens to a substances particles when it dissolves?

A

It’s particles separate and become completely mixed with the particles of the solvent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does soluble mean

A

That a substance is able to dissolve in a solvent

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

What does insoluble mean?

A

A substance cannot dissolve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is filtration?

A

The process by which insoluble substances are separated from soluble substances using a filter

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

What does filtration do?

A

It separates insoluble substances in the solid state from substances in the liquid state.

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

How does filtration work? (Example of sand and water)

A

It works because filter paper has microscopic holes.

When you filter a mixture of sand and water, water molecules are small enough to pass through the filter paper but the larger grains of insoluble sand cannot.

The sand stays behind in the filter paper as the reside while the water passes through as the filtrate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is a filtrate?

A

The liquid that passes through the filter during filtration.

25
What is residue?
An insoluble material left behind during filtration
26
Why do chemists flute their filter paper?
This produces a larger surface area for the filtrate to pass through.
27
What is evaporation?
When a substance turns from the liquid to the gas state at a temperature below the boiling point.
28
What happens if you heat a substance too strongly?
You get a powder
29
What happens if you allow the solvent to evaporate slowly?
You get regularly shaped crystals
30
What is crystallisation?
The process by which crystals are formed during the evaporation of a solvent from a solution
31
How can you tell if a solution is saturated?
No more solute can be dissolved at that temperature.
32
What is solubility?
A measure of how much solute can dissolve in a given solvent at a certain temperature
33
How does crystallisation work?
- You need to heat the solution gently until it is a saturated solution - crystals will start to form at this point so you then let the solution cool slowly. - as the solution cools the solubility of the solute decreases so more crystals form. - you can separate them from the remaining solution by filtration.
34
What equipment is needed for filtration?
Filter funnel with filter paper | Conical flask
35
What equipment is needed for crystallisation
An evaporating basin with the solution A flask with boiling water A tripod Bunsen burner
36
What does simple distillation do?
It separates a solvent from a solution
37
How does simple distillation work?
- it relies on the solvent having a much lower boiling point than the solute - when the solution is heated the solvent boils but the solute does not. - the solvent escapes from the solution in its gas state - it is then cooled and condensed back to its liquid state by a condenser
38
What is condensation?
Changing from the gas to liquid state
39
What is a condenser
A piece of apparatus that is is kept cold using a flow of cold water
40
What is vapour?
A substance in its gas state and below its boiling point.
41
What does fractional distillation do?
It separates 2 or more substances from a mixture in the liquid state.
42
How does fractional distillation work?
- it relies on each substance having a different boiling point. - then both substances leave the liquid mixture as vapours - in the fractioning volume the vapours condense on the inside surface, hearing it up. When the temperature reaches the boiling point of one of the vapours (the one with the lower boiling point) it cannot condense any more so it passes into the condenser. While this is happening the one with the higher boiling point can condense further and water droplets fall back into the flask.
43
What are advantages of the fractioning column?
It has a large SA on which the vapours can continually condense. During fractional distillation it is hottest at the bottom and coolest at the top.
44
What is chromatography
A separation method that relies on the distribution of a substance between a mobile phase and a stationary phase.
45
What is the stationary phase
A substance in the solid or liquid state that doesn’t move during chromatography
46
What is the mobile phase?
A substance in the liquid or gas state that moves during chromatography
47
What are the mobile and stationary phase in paper chromatography?
Stationary phase- absorbent paper | Mobile phase - solvent in the liquid state
48
What is an Rf value ?
It is the relative distance travelled by a substance during chromatography
49
Why do we use Rf values
To compare the spots on a chromatogram.
50
How do you calculate the Rf value?
Distance travelled by substance ➗ distance travelled by solvent
51
What are the stationary and mobile phase in gas chromatography
Stationary phase- silica or alumina powder packed into a metal column Mobile phase- unreactive carrier gas which doesn’t react with the sample
52
What does gas chromatography do?
It separated the components of a mixture and also measures their amounts
53
How does gas chromatography work?
- The sample is turned into the gas state when it is injected into the column. - the carrier gas pushes the sample through the column. - a detector sends a signal to a computer as each component leaves the column. - the computer produces a chromatogram
54
What are the advantages of thin layer chromatography
It is quicker It is more sensitive so a smaller sample can be used There is a larger range of stationary phases and solvents to choose from.
55
How would you separate a mixture of soluble and insoluble substances?
Dissolving followed by filtration
56
How would you separate a solute dissolved in a solvent (a solution)
Crystallisation to obtain the solute, simple distillation to obtain the solvent
57
How would you separate a mixture of 2 or more substances in The liquid state
Fractional distillation
58
How would you separate a mixture of coloured soluble substances?
Paper chromatography or thin layer chromatography

Chemistryyyy (15 decks)

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