Criterion B Lab Report Guide MYP 4-5
This is a student guide for Criterion B Lab Reports. Students should refer to this Guide when
completing a lab write up. Students can choose to use the matching Lab Template.
INTRODUCTION
A company that produces Sulfur dioxide(g) for creating sulfuric acid, which is then used to
produce disinfectant, refrigerant and bleach. This company is looking for a more efficient
way of producing it, and is approaching the way of changing the concentration of solutions.
In this lab, it will be investigated if changing the concentration of sodium thiosulfate would
take less time to produce the same amount of sulfur dioxide.
Background Information
Chemical reactions can be speed up by multiple factors. This process happens when
molecules bounce off of each other within a specific volume of space, which knocks off pre-
existing bonds within the molecules, forming new bonds. One that can speed up this process
is to increase the kinetic energy of the molecules, which is adding heat. Another one is
change the concentration, which is containing more moles of one substance in the same
volume. Lastly, catalyst could be added to the solutions. In this lab, concentration would be
tested. A real life parallel scenario to this would be adding vinegar into a jar with an egg in
order to dissolve the egg shell. If low a concentration (mixed with water) of vinegar is added
into the jar, then it would take a lot more time than to adding pure vinegar. This is due to what
was said above, the concentration. This is connected to the lab since the concentration of
sodium thiosulfate could be changed to reduce the time taken to produce sulfur dioxide. This
will be measured via the opacity of the solution, which is defined by a human eye testing if
an “x” placed behind the test tube could be seen. This is because when it is produced, sulfur
will also be produced, which causes the solution to become opaque, which acts as an
indicator of the process.
Research Question
What is the effect of increasing the concentration of sodium thiosulfate measured in
molarity(M), on the time, measured in seconds, taken for the water to turn opaque (not being
able to see the “x”)?
HYPOTHESIS
It is predicted that the higher the concentration of sodium thiosulfate is, the quicker the
solution will turn opaque. This is because when a higher concentration of it is being added,
the amount of molecules within the test tube would be larger than lower concentrations.
Therefore there are more molecules within the same volume, which would cause more
collisions happening at once. Hence causes the reaction to happen at a quicker rate. This
could be explained by collision theory, which states that all molecules have to collide in order
to react. On the other hand, if the concentration is low, less collisions would be happening in
the same time, thus less reactions would be possible within the same period of time.
METHOD
1. Put the tets tube on a lab stand
2. Add 20mL of hydrochloric acid into the test tube
3. Use a black marker to draw an “x” on a sticky note
4. Stick the sticky note on the other side of the test tube, so that you can see through the
solution
5. Prepare a timer
6. Add 20mL of sodium thiosulfate(xMolarity) into the test tube, and start the timer
7. Wait for the solution to turn opaque, and until you cannot see the x through the solution,
stop the timer
8. Increase the Molarity of the sodium thiosulfate and repeat the previous steps according to
how many trials are wanted
Independent Variable
The Independent Variable of this lab is the concentration of the sodium thiosulfate (20mL)
The concentration of the sodium thiosulfate will be manipulated by increasing 1 molarity for
each increment of change for 3 times starting from 1M.
The IV will lead to sufficient result because every time the molarity of sodium thiosulfate
increases by 1 molarity, the amount of molecules within the test tube will increase, causing
more collisions to happen.
There will be 4 different concentrations, and each of the concentration will have 3 trials. It
will be averaged for each concentration. The data will be averaged by result 1+result 2+result
3/3.
Dependent Variable
The dependent variable of this lab is the time taken for the solution to turn opaque.
The time taken for the solution to turn opaque will be measured through human eye looking
at the “x” behind the solution. The time will be measured by using a timer in the units of
seconds.
QUANTITATIVE OBSERVATIONS
Raw Data Table
What Goes In This Section:
Dependent
Var. Time
Taken for
the solution
to turn
opaque in
seconds
Ind. V. Trial 1 Trial 2 Processed
Concentrati Data:
on of Trial 3 Average
sodium
thiosulfate
in Molarity
(M)
1 70 70 70 70
2 35 35 35 35
20 20 20
3
GRAPHS
ANALYSIS OF THE DATA
As the concentration of sodium sulfate solution being added increases, the time taken for the
solution to turn opaque also increases. This is a direct correlation. This is because when a
higher concentration of sodium sulfate is added into the solution, there are more molecules
colliding with each other at the same time, therefore causing more reactions to happen
(collision theory). That causes the sodium sulfate to react with the hydrochloric acid at a
quicker rate, producing sulfur that turns the solution opaque.
EVALUATION
The data shown above supports the hypothesis made. This is because of sufficient reasoning
while predicting the results. Collision theory explains this experiment very well, therefore the
results are obvious, thus easier to predict. Another experiment supports this: the egg shell
dissolving experiment. As explained above, reactions happen at a quicker rate when high
concentration of solutions are added. This supports the data here, and also the hypothesis
made in prior.
Weakness and type of error How it connects to a variable Impact To Data
The method might have The definition of This might affect the
caused a systematic error, opaqueness is different for precision of the dependent
because the opaqueness of each person, therefore variable, time.
the solution is determined by depending on the person, the
human eye. time taken for the person to
determine if the solution is
opaque might be different.
IMPROVEMENT/EXTENSIONS
The method could be improved thus yielding to a more precise data by having an opaqueness
detector or a standard that determines what exactly is opaque. This can eliminate the
inconsistency of human eye, since it is subjective and would not be 100% precise all the time.
