Name
Date
Pd
Unit 6 – Worksheet 2-key
Why Structure is Important
In the table below, identify the type of solid (atomic, molecular, ionic) each
substance forms. Then predict in which phase (solid, liquid or gas) each
substance would exist on the Earth, on Mercury and on Pluto.
Substance
Crystal structure
NaCl
Type
I
melting pt (°C)
boiling pt (°C)
801
1413
Phase at
room temp
on
Earth
(25°C)
S
Mercury
(450°C)
S
Pluto
(-230°C)
S
CaCO3
S8
Cu
H2O2
I
M
520
decomposes at
825
115
444
E
M S
P
S
E
S
M G
A
M
1084
2567
-0.41
150
P
E
S
S
M
S
P
S
E
L
M G
P
Modeling Chemistry
S
S
U6 ws 2 v1
PbI2
CO2
Ar
402
954
-78
-57
-189
-186
E
S
M
L
P
S
E
G
M
G
P
S
E
G
M
G
P
S
Account for differences in the melting and boiling points of the three types of
structures.
Ionic solids generally have high melting and boiling points due to the strong bonds
connecting the particles in a lattice. The molecules in a molecular solid are not as
strongly attracted to one another and have lower melting and boiling points. In an
atomic solid, if the atoms are not connected (as in Ar), the mp and bp are very low.
In a metallic solid (like Cu), each atom is strongly attracted to all its neighbors, so
these solids generally have high mp and bp.
Predict which of these substances would conduct electricity when molten.
Ionic solids form mobile charged particles when they melt, so they molten substance
would conduct electricity. The electrons in metals are very loosely bound to the
atoms, so a molten metal would also be a good conductor.
Would any of these conduct electricity as a solid?
Only metals conduct as solids, because the electrons are loosely bound to the atoms.
Modeling Chemistry
U6 ws 2 v1