Prediction-
I predict that the powder size CaCO3 will have
the fastest rate of reaction,the small size chips will have the second
fastest reaction rate and the large size chips will have the slowest
reaction rate due to scientific knowledge.
Preliminary
work-
Results for powder...
Ways to improve our method so that accurate and
reliable results can be gained when doing main experiment...
- make sure apparatus are set out well
- when turning measuring cylinder
upside down into the large bowl of water, make sure there are
no bubbles as it might affect the reading. - pour HCl
carefully into the conical flask where the CaCO3 powder are to
make sure there are no spills.
- remember to check the volume of gas every 5 seconds when
doing the experiment
Apparatus-
30 cm of hydrochloric acid
measuring cylinders
Calcium carbonate
(powder,small chips,large chips-must weigh 3g each) stopwatch
scale
goggles
large bowl of water
deliverey tube
conical flask
Method-
1) First, set out equipment
as on the diagram on the next page...
Range of sizes of CaCO3...
- powder
- small
- large
2) Put the required size of CaCO3
into conical flask. It must weigh 3 grams for each experiment so
the results are reliable (use scales). 3) attach deliverey
tube to conical flask. 4) fill a
measuring cylinder completely full of water. Turn it up-side
down into the large bowl of water carefully ensuring there are no
bubbles.
5) Put the other end of the deliverey tube through to the
measuring cylinder.
6) Measure 30 cm of HCl with a measuring cylinder.
Read from the bottom of the reniscus. Must be the exact amount
each time as surface area is the only variable we are changing.
7) Pour HCl carefully into the conical
flask, making sure ther are no spills. Close the lid straight
away. 8) Start the stopwatch
at the same time. Once every 5 seconds, record the volume of gas
produced. Try to get the timing right inorder to obtain accurate
results. 9)
Once reaction has finished, stop the stopwatch and turn the
measuring cylinder right way up with care in order to get an
accurate reading on the downward displacement of water.Read
from the bottom of the reniscus.
Fair testing and safety
procedures... - wear goggles
throughout carring out experiment. -
other variables- concentration, temperature etc- must remain
constant. - repeat each experiment 3 times.
Results-
Powder...
Small chips...
(P.T.O.)
Large chips...
Analysis / Conclusion-
As predicted, the powder CaCO3 had the fastest
reaction rate. At the end of 50 seconds, there was an average of 88 cm
of gas. If you compare the powder results with the other results, you
would see that already an average of 21 cm of gas was produced after
5 seconds, while the others were reacting not as fast. This is because
the acid molecules could hit the most surface area and react. The
more surface area there are, the more collisions there are. Therefore,
the faster the reaction rate.
For the small chips, the three results obtained from the three
experiments are very different from each other (see graph). At the
end of 50 seconds, an average of 76cm of gas was produced. This was
lower than the powder CaCO3, as expected. It did not have as much
surface area as the previous, so there was not as much collisions.
The large chips reacted the
slowest with only an average of 9 cm of gas produce after 50 seconds.
This was due to the fact acid molecules had the least amount of
surface area to work on, therefore, there was even less collisions
occuring than the chips with more surface area.
Overall, the pattern of the results were compatible with
our scientific knowledge and prediction.
Evaluation-
In general, the investigation
went well and the procedure was carried out properly. The general
pattern of the results proved our scientific knowledge and prediction
to be right and the method used was a good one for carrying out the
investigation and obtaining results. However there were anomalous
results and they were likely to be due to...
- the rate in which HCl was poured into the
conical flask. It was noticed that if it was poured slowly than it would
make the reaction rate slower. If it was poured quickly than the
reaction rate was quicker, but with the powder it reacted too quickly
and so some of the solution went over the edge. This could have
affected the reliability of the results.
- when we were reading the volume of gas produced, because
the measuring cylinder was turned up-side down, we could have read
the measurements wrong. This could have also made the results less
reliable. - we have to obtain each result at a short time of 5
seconds, and because we are put under pressure, this could have also
affected the way we read the measurements.
To improve our experiment,
or to gain more accurate and reliable results, I would be more careful
with the issues mentioned above. I would also repeat each
experiment a few more times. Then we could compare these with the
results we already have and could be use to make a firmer conclusion.
However, I did compare my results with those of my friend's. Here are
their results...
Powder...
Small Chips...
Large chips..
Their results are similar to mine as the
collision theory applies to both of our's. From their results the
powder reacted the fastest, then the small chips, than the large chips.
Therefore our results match. For futher
work, I would investigate how other variables affect the rate of
reactions. These other variables are- temperature, concentration and
catalyst.