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Essential Chemistry for IGCSE - Particles And Purification (Section 1)

1
Which of the following is the process of a solid changing directly to a gas?
Answer
(B)
Sublimation
2
What type of experiment is used to demonstrate Brownian motion?
Answer
(B)
Observing the movement of pollen grains in water.
3
What will be the effect of impurities on the melting point of a pure substance?
Answer
(C)
It will decrease.
4
In chromatography, which phase does the mixture travel through?
Answer
(B)
The mobile phase
5
What happens to the particles during the process of evaporation?
Answer
(B)
They gain energy and escape the liquid.
6
What happens to the intermolecular forces when a substance changes from a solid to a liquid?
Answer
(B)
Intermolecular forces decrease.
7
Which technique could be used to separate a solid from a solution?
Answer
A
D
8
What effect do impurities usually have on the melting point of a substance?
Answer
(C)
They decrease the melting point.
9
What is the difference between accuracy and precision?
Answer
(A)
Accuracy measures how close the result is to the true value, while precision measures the repeatability of a measurement.
10
What are the two key factors that must be known to calculate the density of a substance?
Answer
(A)
Mass and volume
11
Which of the following will lower the melting point of a substance?
Answer
(A)
Adding a small amount of an impurity.
12
What is the most appropriate separation technique for separating a solution of salt in water?
Answer
(D)
Distillation
13
Which of the following is most appropriate for separating salt from water?
Answer
(A)
Distillation
14
In paper chromatography, the spot of the sample should be:
Answer
(B)
Above the solvent level
15
How would you describe a 'homogeneous mixture'?
Answer
(B)
A mixture where the components are evenly distributed.
16
What is the process of obtaining pure crystals from a solution called?
Answer
(B)
Crystallization
17
How are particles arranged in a crystalline solid?
Answer
(C)
In a repeating, ordered pattern
18
Why is it important to know if a substance is pure?
Answer
(D)
All of the above
19
What does the kinetic particle theory explain?
Answer
(C)
The behavior of matter in terms of the motion of particles
20
Which apparatus is best suited to measure the volume of 25.0 cm³ of a liquid?
Answer
(B)
A measuring cylinder
21
What is the purpose of filtration?
Answer
(B)
To separate an insoluble solid from a liquid.
22
What is the name of the process when a liquid becomes a gas at its boiling point?
Answer
(D)
Boiling
23
Which of the following is NOT a method to measure volume?
Answer
(D)
Thermometer
24
Which of the following is NOT a state of matter?
Answer
(D)
Solution
25
What observation provides evidence for the kinetic particle model and Brownian motion?
Answer
(C)
The random movement of pollen grains in water.
26
In paper chromatography, what is the stationary phase typically composed of?
Answer
(B)
Filter paper
27
What are the particles in a gas like compared to the particles in a solid?
Answer
(B)
Less ordered
28
Which of the following is/are key to obtaining pure crystals in crystallization?
Answer
A
B
29
Which of these is used to determine how well a separation has worked during chromatography?
Answer
(B)
R_f value
30
If a substance is impure, how will this affect its melting point?
Answer
(D)
The melting point will broaden and decrease.
31
What is the name of the process when a solid becomes a gas without becoming a liquid?
Answer
(C)
Sublimation
32
How are the different components separated in paper chromatography?
Answer
(C)
Based on their solubility and attraction to the paper.
33
What is the fundamental difference between a solid, a liquid, and a gas?
Answer
(B)
The arrangement and movement of the particles.
34
Which state of matter has particles that are most tightly packed and have strong forces of attraction?
Answer
(C)
Solid
35
Which of these techniques is most suitable for separating sand from water?
Answer
(B)
Filtration
36
Which state(s) of matter can flow?
Answer
B
C
D
37
Which techniques are commonly used to obtain a pure substance from a mixture?
Answer
A
B
C
38
What is the purpose of the solvent in paper chromatography?
Answer
(C)
To act as the mobile phase.
39
Which of these techniques can be used to separate mixtures containing liquids?
Answer
A
C
40
What is the purpose of a condenser in distillation?
Answer
(B)
To cool and condense the vapor.
41
In which state of matter are the forces of attraction between particles the weakest?
Answer
(C)
Gas
42
Which of the following processes can be used to purify a solid from a liquid?
Answer
B
C
D
43
Which of the following statements is/are true about the forces between particles in a substance?
Answer
A
B
D
44
Which of these is used in fractional distillation?
Answer
(C)
A fractionating column
45
What does the term 'melting point' refer to?
Answer
(B)
The temperature at which a solid changes to a liquid.
46
Which process involves separating components by their differing solubilities in a solvent?
Answer
(D)
Solvent extraction
47
What is the main purpose of solvent extraction?
Answer
(D)
To separate a compound from a mixture using a solvent.
48
What is the purpose of cooling the flask during fractional distillation?
Answer
(B)
To condense the vapor back into a liquid.
49
What is the best technique for separating different colored dyes in an ink?
Answer
(C)
Chromatography
50
What is the definition of a pure substance?
Answer
(B)
A substance with a fixed composition and distinct properties.