1. A table of results.
|
Iron
|
Paraffin
|
Starch
|
Iron(II)Sulphate
|
Melting Point
|
HIGH
|
LOW
|
HIGH
|
HIGH
|
Solubility in
Water
|
YES
|
NO
|
YES
|
NO
|
Solubility in
Acetone
|
YES
|
NO
|
YES
|
NO
|
Conductivity
|
YES *
|
NO
|
NO
|
YES
|
*Dissolved in a liquid
2. The type of bonding present in each substance.
Iron: metallic
bonding
Paraffin: covalent
bonding
Starch: covalent
bonding
Iron Sulphate:
ionic bonding
3. A secondary table to show “expected” results.
|
Iron
|
Paraffin
|
Starch
|
Iron(II)Sulphate
|
Melting Point
|
HIGH
|
LOW
|
LOW
|
HIGH
|
Solubility in
Water
|
NO
|
NO
|
NO
|
YES
|
Solubility in
Acetone
|
NO
|
YES
|
NO
|
NO
|
Conductivity
|
YES *
|
NO
|
NO
|
YES
|
4. A conclusion comparing the actual results with the expected
results.
As we can see when
we compare our results table and the expected results table, the experiments
with starch didn’t go as expected. Starch is considered a covalent compound,
however the results weren’t as they should be considering the type of compound
it is. This is because starch is an organic compound (more specifically a
carbohydrate). It is a chain of monosaccharide, forming a polysaccharide which
has a very fibrous structure and forms very strong bonds. This is the reason
that it has a high melting point and is insoluble in water. Starch doesn’t
dissolve in acetone because we’re assuming that acetone is a covalent compound
and therefore non-polar. However, acetone is an exception and is polar.
In the experiments
with iron and paraffin, the same happened with the solubility in acetone. The
polarity we were assuming acetone had was non-polar and this is why the results
varied.
Another thing that
shouldn't have happened according to the properties of the metallic bondings is
the dissolution of iron in water and acetone. This could be due to the state of
the iron. Maybe it was in a very light powder and this is the reason why it dissolved.
5. An evaluation that suggests improvements that could be made to your
method.
One of the
problems with this method is timing. We didn’t know the exact time at which the
solute melted or at what precise moment it totally mixed with the solvent
(water and acetone).
We could solve the problem of the melting points by using a Melting Point
apparatus, such as OptiMelt, which gives you the exact temperature at which the
substance melts. We could: use the machine to calculate the melting point of
the four substances, heat each substance (controlling its temperature with a
thermometer) during 3 min, and if in these three minutes the substance hasn't
reached the melting point temperature, it means that it has a high melting
point, while if it has already reached the exact temperature, it means that it
has a low melting point.
Also, we didn’t
wait the same amount of time in each experiment, so probably the results are
very weak and unreliable. This could be solved by using stopwatches and
recording the same amount of time for all the experiments. As we have said
before, 3 min should be enough.
The second problem
is also related to the solubility of the substances. Even if we timed the time
the solute took to dissolve, it would always be a rough measure as we were
seeing it with a naked eye, that is, stopping the stopwatch when we thought the
substance had dissolved. This could be solved by drawing something on a paper,
and placing the test tube or the beaker over it. Thus, when we stop seeing the
drawing, we know that the solute has dissolved.
However, when something dissolves in water the solution will most probably be
transparent so we won't be able to see if it has completely dissolved. To make
sure we have an accurate result we could draw a cross on a piece of paper and
put it underneath the beaker and when the cross is utterly visible we will know
that the substance is totally dissolved because the solution is transparent.
Finally, we think that the results were not as expected because we didn’t use
the same amount of substance in each experiment. This is, we couldn’t analyze
the results equally, as these types of changes in what should be an independent
variable are very significant. This could be improved by specifying how much
quantity of solute we have to use. To obtain a specific amount of solute
of all the experiments we should measure it in a scale. This way will be sure
that the amount is always the same.
6. A minimum of 2 references (APA format)
Green, J., &
Damji, S. (2001). Chemistry (1st ed.). Camberwell, Vic.: IBID Press.
