Based on their structures, explain why sodium oxide, silicon
dioxide and carbon dioxide have different melting points.
Here are 6 real student answers to this question.
For each answer, consider
(a) Have they given the scientifically accepted explanation?
(b) How is the answer structured? Is the structure useful?
(c) Have they used science words and processes correctly?
(Don’t worry about grammar or spelling as long as the meaning
is clear.)
Add any comments and corrections to each answer.
Then put them into a 2-3-1 diamond ranking.
Ambaka
Sodium dioxide, silicon dioxide and carbon dioxide have giant ionic
structure, giant covalent structure and molecular structure
respectively. As the ionic bonds (attractive force) between the ionic
are very strong. Therefore more energy (heat) is required to break
the structure.
Thus, the melting point of ions is very high. The covalent bonds
between the atoms are very strong too. Therefore, more energy
(heat) is also required to break down the structure. The melting
point is very high. The Van der Waal’s force between the molecules
is weak. Therefore, less energy (heat) is required to break the
structure slowly. Thus, the melting point of the molecular structure
(carbon dioxide) is low.
Ben
As 3 of them have different structures, the strength of
their attractive forces are different. And different strength
of attractive forces cause different melting points. For
silicon dioxide, it has giant covalent structure. It’s
attractive bonds are covalent bonds, and covalent bonds
are strong force. For sodium oxide, it has giant ionic
structure, it’s attractive bonds are ionic bonds, and they’re
also strong force but not the same as that of covalent
bonds. For carbon dioxide, it has, it’s attractive force is Van
D W’s force, it’s a very weak force. As higher melting point
is needed to melt stronger force, difference strength of
force cause different melting point.
Catia
For sodium oxide, it’s an ionic compound. The ionic bonds between
the ions are strong. Therefore, large amount of energy is required
to break down the structure of sodium oxide as it has a giant ionic
structure.
For silicon dioxide, it’s a covalent compound. The covalent bonds
between the atoms are very strong. As the result, a very strong
energy is required to break down the silicon dioxide because it has
a giant covalent structure.
For carbon dioxide, it just has a simple molecular structure. The
Van der Waals’ force between the molecules is weak so that a less
energy is required to break it down.
Therefore, sodium oxide and silicon dioxide both have a higher
melting point. But carbon dioxide doesn’t.
Deshal
Sodium and oxygen combine to form sodium oxide by ionic bonds.
Two sodium ions lose one electrons in order to become stable as
well as an oxide ion receives two electrons to become stable. Then,
it has a giant ionic structure that large amount of energy is required
to break it down, so it has a high melting point.
Silicon and oxygen combine to form silicon dioxide by covalent
bonds. Silicon and oxide both share their electrons to become stable.
Then, a giant covalent structure is obtained that the giant covalent
structure require a large amount of energy to break it down. So
silicon dioxide has a very high melting point.
Carbon and dioxide combine to form carbon dioxide. But the Van
der Waal’s force between the molecules is weak. Because carbon
dioxide has a simple molecular structure that it can be broken down
easily.
Erika
The three compounds have different melting points
because they have different structures.
Their form of compounds are different. Some are solid and
some are liquid and gases. Solid have a higher melting
point compare with liquid and gases as the attractive
forces between them are stronger.
For the solid elements, some are metals and some are
non-metal. Metals have a higher melting compare with
non-metals as its ionic bonding is stronger. This lead the
difference of melting point on different compound.
Faisal
Sodium oxide is a giant ionic structure. It has a very high
melting point as the ionic bond is very strong between
them. More force is required to break down.
Silicon dioxide is a giant covalent structure. It also has
the highest melting point because the covalent bonds
between them is the strongest.
Carbon dioxide is a simple molecular structure. It has a
lower melting point since the van der Waals’ force
between them is not as strong as ionic bond and
covalent bond.