Amy Kiefer, Jessica Tierney
3 2 1 MELT DOWN!
Introduction (Table of Contents)
The definition of solubility
is the amount of substance that will dissolve in a given amount of another
substance (Webster 1936). The rate of
solubility is the amount of time it takes a substance to dissolve in another
substance. The substance, which
dissolves, is the solute (Webster 1936).
The substance capable of or used in dissolving something is the solvent
(Mebane 1985). The sugar cube is the
solute and the water is the solvent.
Temperature
increases the rate of solubility. If
you put salt into a tube of cold water some salt will dissolve, but if you then
heat the tube more salt will dissolve in the warmer water (Ardley 1984). As the temperature increases or decreases so
will the rate of solubility, because heat can travel through solid objects
faster (Walpole 1995). We will graph
the changes in the rate of solubility.
When
there is a greater amount of substance on one side of a mixture then the other
side, a downhill transport occurs which is called diffusion (Duve 1984). When a solution reaches its equilibrium
diffusion stops. Equilibrium is when
there is a state of balance (Webster 1936).
So when there is a large amount of sugar cube at the bottom of the glass
we know that the sugar cube has met its solubility (equilibrium).
The purpose of the study is to find temperatures impact on the rate of solubility of a sugar cube. From our resulting data we will create charts and graphs.
Many
aspects effect solubility: Temperature, pressure, and equilibrium of solute
versus solvent (Ardley 1984). So it
would be in our best interest to manipulate these areas and find the optimal
conditions for solubility.
Temperature
will be manipulated through the water temperature. Since temperature flows through solid and liquid objects we can
increase or decrease the temperature of the sugar cube (Walpole 1995). As the temperate of the solute increases or
decreases the rate of solubility will increase or decrease (Ardley 1984).
Our
hypothesis is that a change in temperature will result in a change in
solubility. As we increase the
temperature we believe that the solubility will also increase. We are certain of this because when a
substance is heated its molecules move faster, increasing the rate of solubility. This theory is referred to as entropy.
MATERIALS (Table of Contents)
·
ruler
·
bowl
·
glass
·
syringe
·
sugar
cubes
·
duct
tape
·
timer
(stop watch)
·
thermometer
·
water
(hot and cold)
METHOD (Table of Contents)
In order to prove our
hypothesis, that an increase in temperature causes an increase in solubility,
we are going to dissolve sugar cubes using both hot water and cold water. We hope to show that hot water will dissolve
the sugar cube faster than the cold water.
We begin our experiment by setting up an apparatus. This apparatus consists of a glass bowl in
which an upside-down glass sits. The
base of this glass is therefore in the air, our sugar cube resting upon it. The glass we choose to use is a wineglass
because it has a small base, allowing room for the cube, yet preventing
puddling. The water should flow off the
glass into the bowl. This keeps sitting
water from dissolving the cube and ruining data. Next we connect a ruler to the side of the bowl. This is to keep us from changing the length
of the water flow.
Following this we fill a syringe first with cold
water. Holding the syringe at the 8cm
mark on the ruler, above the cube we started our timer. At the same time we begin pushing the water
out of the syringe at a constant rate until it is empty. This syringe is filled with 60 ml of water
each time, and the process is repeated 10 times. From here we will repeat the whole process using hot water. Our data for time varies only 3 seconds
(each trial taking between 4 and 7 seconds) showing we are keeping the rate of
water flow basically constant.
RESULTS (Table of Contents)
The actual experiment seems
to be a success; the hot water is obviously melting the cube faster than the
cold water. However we still need to
analyze our resulting data. From here
we put our collected data into two charts.
One chart, page 5, is the information yielded from the cold water trials
and the other chart, page 6, is the information yielded from the hot water
trials. Each chart includes five
things: the temperature of the water, the amount of time each trial takes, the
percentage of the cube that dissolves, the dissolving rate, and the flow rate
of the water. These charts allow us to
analyze the information from each experiment separately; they are shown below. From here we put both the cold water and hot
water data into one graph, page 7, in order to compare the two. Our x-axis is the temperature of the water
during a trial, and the y-axis is the amount of the sugar cube dissolved during
that trial. This graph shows us that
the hotter temperatures have a faster dissolving rate. To find the dissolving rate we take the
percentage dissolved during the trial and divide it by the amount of time that
trial takes. The graph is shown below. The next graph, page 8, shows, yet again,
that hotter temperatures cause the cube to melt faster. Our x-axis is temperature and our y-axis is
percentage dissolved. The last graph,
page 9, shows that flow rate does not have a strong impact on the percent
dissolved. This leaves the main factor
to be temperature. Our x-axis is the
flow rate and our y-axis is the percent dissolved. In order to find the flow rate of each trial we take our 60-ml of
water and divide it by the amount of time that trial takes.
DISCUSSION (Table of Contents)
Our overall analyses of data, and the experiment in
itself, show us that hotter temperatures do increase the rate of solubility of
a sugar cube. We used the process of
trial and error in order to come up with a working apparatus and experiment. We began using a completely different set
up, and even a different solute altogether.
We started with sweet tarts and a contraption that looks like this. 
However, how accurate our experiment and data
collected from that experiment is, is another question all together. Many variables in our project are not accurate
because the are not monitored closely enough.
The first variable is time; data shows that our time uncertainty is 3
seconds. This may seem as though we
control the time pretty well, and as though it was basically constant. On the contrary, since our longest time is
only 7 seconds a 3-second difference doubles the amount of time the experiment
lasts. This tells us that in a future
trial we need to have one set time. Also
our temperatures differ. Yes we need
two temperatures, a cold and a hot in order for the experiment to work, but we
should have had one set cold temperature and one set hot temperature. Our cold-water temperature stays at 70
degrees, which is good, but our hot-water temperature keeps dropping too
quickly. In order to keep the data more
accurate and easier to compare we need to find a way to keep the hot water
constant as well as the cold water. In
order for an experiment to be accurate there should only be one changing
variable, we have two, the time and the temperature. We need to decide whether our temperature or our time is going to
be the changing variable not both. Over
all this experiment gives us a successful conclusion data-wise, but leaves more
to be desired from the accuracy of the experiment itself. In the future, along with keeping only one
changing variable, other changes can be made to this experiment. For example pressure can be added into
consideration, along with diffusion and equilibrium. However, our data supports our hypothesis showing that however
limited the topic, we have a successful experiment.
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This graph shows the correlation between temp. and dis. rate
This
graph shows %dis. with the water speed
This
graph shows the %dis. with temperature
LINKS (Table of Contents)
DATA LINK
http://library.thinkquest.org/2690/exper/exp23.htm - This is an similar experiment on solubility that you can perform on your own.
http://www.akucell.com/solu.htm - Shows temperatures impact on solubility with processed foods