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Essential Chemistry for IGCSE - Particles And Purification (Section 7)

1
Which of the following is a key characteristic of a pure compound?
Answer
(B)
A sharp melting point.
2
What will happen to the rate of diffusion if you decrease the concentration gradient?
Answer
(B)
It decreases.
3
What term describes the change of state from a solid directly to a gas?
Answer
(C)
Sublimation
4
Which purification method is most appropriate for separating two liquids that form a homogeneous mixture?
Answer
(B)
Distillation
5
Which of the following is an example of sublimation?
Answer
(C)
Dry ice (solid CO2) turning into gas.
6
If two gases at the same temperature are allowed to diffuse, which gas will diffuse faster?
Answer
(B)
The gas with a lower molecular mass.
7
What property does paper chromatography exploit to separate the components of a mixture?
Answer
(B)
Different solubilities and affinities for the stationary and mobile phases.
8
Which parameters are crucial for determining a substance's purity?
Answer
A
B
C
9
What is the relationship between pressure and volume for a gas (at a constant temperature)?
Answer
(A)
As pressure increases, volume decreases.
10
In chromatography, the stationary phase is:
Answer
(B)
The medium that does not move
11
What is the name of the process when a gas changes directly into a solid?
Answer
(C)
Deposition
12
If you increase the temperature of a gas, what will happen to its particles?
Answer
(C)
They will move faster.
13
In paper chromatography, what is the role of the paper?
Answer
(C)
Stationary phase
14
Which of the following is a characteristic of a good solvent for recrystallization?
Answer
(C)
It dissolves the desired compound well when hot and poorly when cold.
15
If you add energy to a substance, what happens to its particles?
Answer
(C)
They move faster.
16
What is the key idea behind the kinetic particle theory?
Answer
(B)
All matter is made of particles in constant motion.
17
What are the key concepts when identifying a pure substance?
Answer
A
B
18
Which is the key apparatus in a fractional distillation setup?
Answer
(C)
Fractionating column
19
What does the term "eluent" refer to in chromatography?
Answer
(B)
The solvent used to carry the sample components.
20
Which of the following statements is NOT a key point of the kinetic particle theory?
Answer
(C)
The particles are attracted to each other.
21
Which purification technique relies on different solubilities in two immiscible solvents?
Answer
(C)
Extraction
22
Which purification method is best for separating a solid from a liquid?
Answer
(B)
Filtration
23
In paper chromatography, what is the function of the developing solvent?
Answer
(B)
To carry the components up the paper
24
Which purification process utilizes two immiscible solvents?
Answer
(B)
Extraction
25
What does the kinetic particle theory state about particles?
Answer
(B)
They are in constant motion.
26
What type of energy does a substance have when it is changing state?
Answer
(B)
Potential energy.
27
Which factor influences the speed of diffusion?
Answer
(A)
The mass of the particles
28
What is the purpose of using a drying agent?
Answer
(A)
To remove water from an organic solvent
29
What is the fundamental building block of matter?
Answer
(B)
An atom
30
What would cause a sample to have a wider melting point range?
Answer
B
C
31
What are the steps involved in separating sand and salt using the described method?
Answer
A
B
C
32
Which of the following affects the melting point of a substance?
Answer
A
B
33
How do impurities affect the melting point of a substance?
Answer
(C)
Impurities lower the melting point.
34
Which method would be most appropriate to separate ethanol from water?
Answer
(C)
Simple distillation
35
In paper chromatography, what is the name of the liquid that moves up the paper, carrying the sample?
Answer
(B)
The mobile phase (solvent).
36
What happens to the kinetic energy of particles when a substance is heated?
Answer
(B)
It increases.
37
What does the Brownian motion experiments help explain?
Answer
(B)
That the particles are in constant motion.
38
What is the effect of an impurity on the melting point?
Answer
(B)
Decreases it
39
Which of the following is used to separate two or more liquids that are miscible?
Answer
(C)
Distillation
40
Which of the following will increase the rate of diffusion?
Answer
A
D
41
Which of the following methods can be used to separate mixtures?
Answer
A
B
C
42
Which factors influence the Rf value in paper chromatography?
Answer
A
B
C
43
What is meant by the term 'concentration gradient'?
Answer
(B)
The difference in the amount of a substance in two areas.
44
What is the name given to the change from a liquid to a gas?
Answer
(B)
Evaporation
45
Which of the following methods would be the best for separating iron filings from sand?
Answer
(C)
Using a magnet
46
What happens to the particles during boiling?
Answer
(D)
They increase their kinetic energy and decrease the forces holding them together.
47
What are essential steps in recrystallization?
Answer
A
B
C
48
What is the basic unit of all matter?
Answer
(B)
An atom
49
Which of the following are methods that can be used to separate a mixture?
Answer
A
B
C
D
50
What is a molecule?
Answer
(B)
A group of atoms bonded together.