rate of reaction.
1.The temperature increases the number of collisions. When the
temperature is increased the particles all move quicker therefore there
will be more collisions
2. Concentration or pressure increases the number of collisions. If the
solution is made more concentrated it means there are more particles of
reactants knocking about the water molecules, which makes collisions
between particles more likely. In a gas increasing the pressure means the
molecules are more squashed up together so these are going to be
collisions.
3. The size of solid particles or surface area increases collisions. If one
of the reactants is a sold then breaking it up into smaller pieces will
increase the surface area. This means the particles around it in the
solutions will have more area to work on so there’ll be more useful
collisions.
4.catalyst
4.Catalyst increases the number of collisions. A catalyst works by giving
the reacting particles a surface to work on where they can bump into
each other. This obviously increases the number of collisions.
Faster collisions increase the rate of reaction. Higher temperature also
increases the energy of the collisions because it makes all the particles
move faster. Increasing the temperature only causes faster collisions.
Reactions only happen if the particles collide enough with enough energy
to make the reaction happen. This initial energy is known as the activation
energy and it’s needed to break the initial bonds.
Variables
The independent variable is the variable is to be changed. In this case
the independent variable is the concentration of Sodium Thiosulphate
solution. In this experiment the concentration of the Sodium
Thiosulphate solution to be used are:
? 50g/L
? 40g/L
? 30g/L
? 20g/L
? 10g/L
This range should be sufficient to give me adequate data to prove or
reject my predication.
The dependant variable is the variable to be measured. Therefore the
time taken for the cross to disappear is the dependent variable in this
experiment. The constant variables are the ones, which are to, be kept
the same (constant) to make sure that the test is a fair test.
Therefore the constant variables will be:
? No catalyst to be used~~ As the reaction is quick anyway
? Stirring~~to be done at the same constant rate or not at all.
? Volume of HCl~~ it will always be 5.0cm
? Concentration of HCl~~ will always be 0.5M
Fair testing
? To make the experiment is a fair rest a number of things would
needed to be done. Firstly one way to make sire that the test is an
fair rest is by using the same equipment all the time for the whole
experiment.
? Furthermore to make the experiment fair I would use the same
concentration and the same amount of hydrochloric acid.
? Also to keep it a fair test I would not use any catalyst at all for
each part of the investigation.
? Also to keep is an fair test I would not use any catalysts at all for
any parts of the experiment. Also I would not stir the solution at
all. Additionally to keep it an fair test I would swirl the flask same
amounts of swirls for each part of the experiment.
? Furthermore the temperature will be room temperature for all
parts of the experiment and I will use the same volume of sodium
Thiosulphate of an particular concentration.
? The main thing is that because I will investigate the affects of the
concentration of sodium Thiosulphate solution on rate of reaction I
have to keep all other variables that affect the rate of reaction
constant to keep it an fair test.
Accuracy
? To keep the investigation accurate I would have to use the most
suitable equipment. Therefore measuring the volume of the
chemicals I would have top use the correct measuring cylinder.
? Also for accuracy I will also look at the cross form the same
distance and angle.
Reliability
? To make the results reliable the experiment shall be repeated to
an minimum of three times but it could be repeated more than
thrice to give much reliable set of data. After experiment has
been completed three times or more than an average is to be
worked out.
Prediction
? I predict that as the concentration of Sodium Thiosulphate is
increased, the less time it will take for the solution to become
cloudy. This is because there are more particles of reactants
knocking about the water molecules . therefore the number of
collisions is increased.
? Also as the concentration of Sodium Thiosulphate is decreased,
the more time it will take for the solution to become cloudy. This is
because there are less particles of reactants knocking about the
water molecules . therefore the number of collisions is decreased.
Apparatus
Equipment
? An X on a card or paper.—I need the card it put under the conical
flask to see if it is visible when the reaction is on going.
? 1 Measuring Cylinder—measuring 50cm3—this is needed to measure
the volume of sodium Thiosulphate
? 1 measuring cylinder measure 50cm3 -this is needed to measure
the volume of distilled water
? 1 measuring cylinder measuring 10cm3- this is needed to measure
the volume of hydrochloric acid
? Timer- time how long it takes for the cross to disappear.
? Conical Flask measuring—100cm3 for the reaction to take place in.
Chemicals
? Distilled Water—To dilute the sodium Thiosulphate
? Hydrochloric acid—for the solutions to react with (0.5m)
? Sodium Thiosulphate—to increase the concentration(50.0 g/L)
(stock solution provided by teacher)
Method
1.measure and pour 50.0cm3 Sodium Thiosulphate solution into 100cm3
conical flask
2.make an X on a piece of card or paper and put the flask on top of
the card.
3.measure and add 5.0cm3 of hydrochloric acid. Starting the timer at
the same time swirl the flask around three times to mix the chemicals.
4.once the solution has become cloudy sop that the ‘X’ cannot be seen
stop the clock and note down the time,
5.once the time has been noted then wash the flaks several times with
tap water and ten an final rinse with distilled water.
6.then repeat the above (1-5) three times using the same
concentration of sodium Thiosulphate.
7.then using the same method as before put the same chemicals in the
conical flask but this time only 40.0cm3 Sodium Thiosulphate to be
used and 10.0cm3 water to be used. But only 5.0m hydrochloric acid is
to be used.
8.once the sodium Thiosulphate,. and water has been put in the flask
and adds 5.0cm3 of hydrochloric acid. Starting the timer at the same
time swirl the flask around three times to mix the chemicals.
8.once the solution has become cloudy sop that the ‘X’ cannot be seen
stop the clock and note down the time,
9.repeat this part of the experiment three times as well.
10.once the second time has been noted then washout the flask
several times using the same method shown in step 5
11.Repeat the experiment using these amounts. Do each amounts
thrice before moving onto the next row.
Sodium
Thiosulphate
water
30.0cm3
20.0cm3
20.0cm3
30.0cm3
10.0cm3
40.0cm3
12.in all cases 5cm3 of hydrochloric acid is to be used. Then after all
the data has been collected then do an average of each of the three
times.
Safety
General Safety.
1. wear goggles(to protect eyes)
2. tie hair/scarves back (to avoid them getting in the way of any
chemicals or fire)
3. put bags/coats out of the area where you or anyone else is working.
(avoid people falling over. Especially with equipment in their hands.)
4. stand up whilst conducting the experiment. (if a chemical spills its
easier to bet away.
5. walk with chemicals and equipment. (if anyone were running then
things may get split and may hurt themselves especially with
glassware and other chemicals)
6. do not alter or disturbs anyone else’s work( it will cause there data
to be wrong and it is not fair.
Safety needed in this experiment
1. follow all general safety rules (it is always need dangerous or not.
It I still needed.
2. Make sure people who have asthma have their asthma pump(they
could have an asthma attack as sulphur dioxide is being given off
during this experiment)
3. Close all chemical bottles (to avoid spillage)
4. Make sure all glassware and equipment is on the middle of the
table. (if it was on the edge then the probability of it falling is
much higher.
5. be careful with using the acid.(acid is corrosive—Could Cause
Burns)
6. Do the experiment in an well-ventilated room. (sulphur dioxide is
being given off.
Results
Volume of
sodium
Thiosulphate
(Cm3)
Volume
of
water
(cm3)
Concentration
(g/L)
Time
1
(S)
Time
2
(S)
Time
3
(S)
Average
time for
cross to
disappear
(S)
Rate of
reaction
(S 1)
Volume
of
acid
HCl
(Cm3)
Time taken for the
cross to Disappear.
50.0
0.0
50.0
33.
49
42
42
0.0238
5.0
40.0
10.0
40.0
43.
93.
47.
61
0.0164
5.0
30.0
20.0
30.0
67
75
75
72
0.0139
5.0
20.0
30.0
20.0
115
164
129
136
0.0074
5.0
10.0
40.0
10.0
208
199
250
219
0.0046
5.0
Results analysis
I found out using the table the pattern and the rate of reaction. The
pattern in the results how is that thee concentration of sodium
Thiosulphate affects the time taken for the cross to disappear. As you
go down the results table, the times gets slower for the solution to get
cloudy there was an reading which is not on the pattern trend. Which is
on the time 2 column and the 40.0cm3 row. It says the time taken was 93
seconds. I realised that this was an error because it was higher than the
next row which does not fit the pattern trend also the other times on
either sides were different and far apart than the middle column. This
error may have occurred because may be to less acid was added or too
much water or the Sodium Thiosulphate solution was less. This shows it
was an good idea to do the experiment thrice because you can easily see
the error and where it was done. Also the error will not fit the pattern
trend. The average time did follow the pattern trends which made it
easier to prove my prediction and plot the data onto a graph easily .in
general my table of results shows as the concentration of sodium
Thiosulphate increased the time taken for the cross to disappear
decreases. when the concentration was 10.0g/L the average time taken
for the cross to disappear was 219 seconds. But when the concentration
of the sodium Thiosulphate solution was increased to 50.0g/L the average
time taken became 42 seconds. I calculated the rate of reaction dividing
1 by the average time taken for the cross to disappear. The data is in the
results table. The rate of reaction data shows that as the concentration
of sodium Thiosulphate increases he rate of reaction increased. When
the concentration was 10.0g/L the rate of reaction was 0.0046 s-1 but
when the concentration was 50.0g/L he rate was faster at 0.0238 s-1
Trends shown on the graphs.
I drew 2 graphs to represents my data and my findings to the
experiment. The first graph graph A was the concentration of sodium
Thiosulphate against the time in seconds. Which was varying from the
lowest average time form 42 seconds to 219 seconds being the highest. I
drew a line of best fit, which was an curve it went from top of the graph
to the bottom. There were some points, which were not touching the line
of best fit. The graph shows that the higher the concentration the less
times for the cross to disappear. Furthermore the highest concentration
which was 50g/L took the lowest amount of time to for the laminated
cross to disappear. Whereas the lowest concentration 10g/L took the
longest amount of time as the graph shows the differences between the
two. The second graph graph b was showing the rate of reaction against
the concentration of sodium Thiosulphate . I drew a line of best fit. the
graph shows that the lower the concentration the lower the rate. The
graph therefore followed my prediction. Form graph b I can see that
when the concentration of the solution was 30g/L the rate of reaction
was 0.0139s-1 and when the concentration was 10g/L the rate form graph
b was 0.0046. in general when the concentration of sodium Thiosulphate
doubled the rate of reaction also doubled.
Conclusion
My data shows that the prediction that I made about the experiment was
correct which was as the concentration of the sodium Thiosulphate gets
higher, the less time it will take for the solution to become cloudy. That
is as the concentration increases the rate also increases. Also as the
concentration of Sodium Thiosulphate is decreased, the more time it will
take for the solution to become cloudy. This is because there are less
particles of reactants knocking about the water molecules . therefore
the number of collisions is decreased. this because of one of the basic
fact about rates of reactions if the concentration of sodium Thiosulphate
is higher then it means what there are more particles of reactant
knocking about, which makes collisions between particles more likely.
Therefore if the concentration was lower then the particles will be less
likely to collide and it will collide much slow. The experiment which was
conducted in a laboratory has followed my prediction all the way through.
The evidence is my data collected. It followed the pattern trend all the
ay through. This shown that my prediction is correct is form the result,
which I ended up with, are table drawn up and the graph showing the line
of best fit. In an nutshell the evidence shown to that my prediction is
strong because the results provide strong evidence t9o support my
prediction
Further work which could be done to look at the rate of reaction of
sodium Thiosulphate that
? The temperature of one of the reactants could be changed to show
how long it will take for the cross to disappear. It will also show
how the rate of reaction is affected.
? A catalyst could be added and we could see how this differs in the
reaction time for the cross to disappear
? Also instead of changing the concentration of sodium Thiosulphate,
the concentration of hydrochloric acid could be changed. Then we
could measure how long it takes for he cross to disappear. Also we
could see how it differs how sodium Thiosulphate.
Evaluation
Why was the investigation successful
The investigation as successful because the minimum requirements of the
experiment we needed to do was done. Also we managed to finish the
experiment to a minimum of three times. We also had all the method and
equipment list in pour exercise books to use. That is we planned the
experiment thoroughly making sure it was an fair test. Also a results
table was already drawn up which helped us to write up all the data and
what amount s we were using of each substance. Also we had the columns
clearly labelled with the heading and the units. It was easier to write
down our data and interpret the findings. Also to keep the experiment
accurate and successful we measured volumes of the reactants at eye
level and same angle and distance. We were sure that the cross had
disappeared because we made sure not an sight of the cross was visible.
Also to keep the it a fair test we watched the reaction form the same
distance and angle and the same pair of eyes. Furthermore I made sure
that I stirred the flask at a constant time and sand the same manner.
These things made the investigation successful. The planning part was
most important and during the experiment I observed all safety
precautions to ensure that the study was successful.
What problems occurred why do you think they occurred
The problems that occurred during the experiment are that one of the
sinks was blocked with pieces of paper thrown down it. This therefore
wasted some time to get the paper taken out by the teachers. If this was
not done then we could have finished it to a minimum of three times but
we were lucky that we got to finish it at an minimum of three times. Also
another problem as that the temperature. The temperature of our hands
may have affected the rate of reaction and also the room temperature
but the room temperature was constant to improve the experiment I
should have noted the temperature and may be place the reaction flask in
a water bath to control the temperature better. Furthermore an problem
was that the sulphur, which was an product of this reaction, is a solid and
it was deposited at the bottom of the flask. So cleaning the flask was
hard. An major problem with this experiment is using the naked human
eye to judge or decide whether the black cross at that bottom of the
flask had completely disappeared. Even though we looked at the cross
from the same distance and angle it was still hard to decide the exact
moment when the cross-had disappeared if I could ,this area needed t o
be improved. one way this could be done would have been to use a
electronic method to decide when the reaction mixture had become
sufficiently cloudy. A beam of light would have been passed through
reaction mixture and when the mixture became cloudy the beam of light
of light would be broken and the sensor of the other end would have
stopped the timer automatically. this would have been very accurate way
of timing the reaction.
How organised were we in our groups? how well did we work
together?
We were well organised in our group because we had all the equipment-
looked aftered well and the result table and pens was all with us, we
quickly got in to our groups. We cooperated well with each other in our
groups .also we took equally part in the experiment. we managed to
complete the experiment three times for each concentration of sodium
Thiosulphate .this was because we knew what to do and had everything
organised. this was by while one person watched over the time and the
product the other person measured the reaction for the next part of the
experiment . this saved a lot of time, and this therefore meant that we
could swiftly on easily move on to the next part of the experiment.
How well do you think you’ve completed the experiment?
why?
We completed the experiment quite well. This was mainly because of the
cooperation within the group members and organisation .we all had an
equal part in the experiment and we all did equal things such as measuring
the reactants , watching the time. The factor, which contributed to the
experiment to be successful ,is having everything organised and good
planning. Equipment, results table and stationary needed. All the
equipment was well provided by the teacher and all the rules were well
explained as well as the explanations.
What improvements can be made? how and why?
The improvements that can be made for reliability is by doing the
experiment more than three times so we can have a higher reliability
table. This can be done by the main factors ,which is organisation and also
we can follow by what we did by saving time . this then will give us the
opportunity to do the experiment more than three times for each
concentration of sodium Thiosulphate. Therefore a higher reliable table
ill is shown in the graph and table. This will be a much more stronger
evidence to follow and support my prediction.
How good is my data and how well does it follow my
prediction
The data, which I got fully, supports the prediction that I have made at
the star of the investigation. I got good data because I planned the
experiment well. I carefully worked in the lab I’ll say that my data was
good because more of my data points were on or close to the best fit
lines I drew graph A and graph . looking at graph A two data points one
for 40.0g/L and the other for 30g/L were not on the best fit line they
were quite close. The reason why they are not on the best fit line
because of experimental error. The data points at 30g/L was a little out
but it could have been due to the way I drew the line of best fit or be an
error in the way I made the solution or the timing of the cross
disappearing. With Graph B 3 data points were on the best fit line but
two at 20.0g/L and 40.0g/L were lower than expected. These two data
points seem to be my anomalous results.
Percentage Error for 20g/L =0.0095-0.0075 X100 =21%
0.0095
percentage error for 40g/L =0.0190-0.0165 X100 =13%
0.0190
For all the other data points 10.0g/L and 20.0g/L and 30.0g/L the
percentage error was about 0%. These data points were on or very close
to the line of best fit in graph B. The reason for the anomalies data for
20.0g/L and 40.0g/L could be because I made the concentration of
sodium Thiosulphate to dilute than it should be. Another reason may be
because I did not time the reaction properly and I was late in stopping
the timer when observing the black cross. The reason is more likely as I
was very careful when I made the various concentrations of sodium
Thiosulphate from the stock solution given to us. I also did have problems
deciding when to stop the time because sometimes I was thinking to
myself has the cross disappeared. This bit of the experiment was flawed
and not very precise despite my attempts. One way round this would have
been to increase e the reliability of data but repeating the experiment
more than three times so around eight or nine times for each
concentration. The only problem is I would have taken more time then we
had available. Overall my data is strong evidence that supports my
prediction.
Self Evaluation
I think and I am sure that I did what was needed to do in the
experiment. I had an equal part in it. I had listened quite well to
instructions also I had an a good plan and table drawn up to help me write
in the data. This made the experiment went well.
Sumaiya Vora 10z Science coursework Page 17 of 17