CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Four powdered substances—A, B, C, and D—were analyzed. The measured physical properties are summarized in the table below.
Property
A
B
C
D
Melting point (°C)
40
1120
350
>2000
Electrical conductivity as a solid
none
none
high
none
Electrical conductivity when melted
none
high
high
none
Hardness (Mohs scale)
1.5
7
3
9
Vapor pressure at 25 °C
4 kPa
<0.01 kPa
<0.01 kPa
<0.001 kPa
Respond to the following.
(a) Classify each substance (A–D) as an ionic solid, a covalent network solid, a molecular solid, or a metallic solid. Justify every classification by citing one property from the table for each substance.
(b) The melting point of substance D could not be measured precisely in the available apparatus. Propose an additional qualitative or quantitative test that would help confirm your classification of D and describe the expected outcome if your classification is correct.
(c) Based on the data in the table, which substance has the highest vapor pressure at 25 °C? Explain your reasoning in terms of the types of forces present in the substance.