Science Investigation Essay, Research Paper
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Science InvestigationInvestigation:I have performed an experiment in order to see the
effects of varying the concentration of reactants on the reaction between
hydrochloric acid and marble chips. Planning: The experiment I have performed involved the
reaction between hydrochloric acid and calcium carbonate (marble chips) to
produce calcium chloride, water and carbon dioxide. The chemical equation for
this reaction is:?????????????????????? CaCO3? + 2HCl????????????? CaCl2
??+ H2 O + CO2Background Information:In order for a reaction to occur particles of the
reactants must collide with a certain minimal energy in order for products to
be produced.? This minimum energy must
be supplied in order to break the bonds in the reactants and allow new bonds to
be formed.There are a number of variables that will affect the
rate of a reaction.? In order to create
a fair investigation these variables must be examined and controlled so that
accurate results can be obtained and conclusions drawn.i)
Temperature-Increasing
temperature increases the kinetic energy of the particles.? This means that collisions between reactant
particles becomes more frequent and occurs with more energy.? Since a greater proportion of the particles
have sufficient energy to break the bonds in the reactants, more products can
be formed increasing the rate of reaction.??
In this investigation, temperature will be kept constant at room
temperature so that only the effect of concentration is being measured.ii)
Catalysts-Catalysts increase the rate of reaction by providing
an alternative pathway for the reaction to proceed that requires less energy
and therefore takes place more quickly.?
In this investigation, a catalyst will not be used since the reaction
should take place sufficiently quickly for accurate measurements to be taken. iii)
Surface Area-An increased surface area increases the number of
collisions between the reactants.? This
increases the number of collisions likely to be successful and therefore
increases the rate of reaction. In this investigation the size of marble chips
(used as a source of calcium carbonate) will be kept as constant as possible so
that only the effect of varying concentration is being measured. iv)
Concentration-Increasing
the concentration of reactants increases the number of particles available for
collisions and therefore the number of particles that can be converted in to
products, increasing the rate of reaction.Apparatus list: Marble chips (Calcium carbonate) Stop-clock Connection tube Retort stand Digital scales Boss and clamp Conical Flask Safety goggles Paper towels Mat Gas cylinder Rubber bung Hydrochloric acid Measuring cylinder Method:I first set up the apparatus as shown in the
diagram below. I used digital scales to weigh 6 sets of 15 ?medium?
chips individually at 3.0 grams and separated them into different beakers.
Then, using a measuring cylinder, I measured out 0.5, 1.0, 1.5 and 2.0M of
hydrochloric acid from the containers and into separate beakers. I then
collected the retort stand, boss and clamp and set them up in the correct
position. I collected a mat and conical flask, placing the flask on the mat in
front of the stand. I then collected a gas syringe and fixed it into the clamp
by tightening it at the middle of the syringe. I collected a rubber bung and
fixed the connection tube that comes with the gas syringe all the way through I
took the first set of 15 marble chips and tipped them into the conical flask. I
took the first beaker of (0.5M) hydrochloric acid, and poured the contents into
the conical flask, and then quickly fixed the connected bung into the top of
the flask, simultaneously starting the stop-clock. Then, every 10 seconds I
took a reading from the gas syringe of how much gas had been produced. I
continued for 3 minutes (180 seconds) or until the gas syringe has reached the
maximum volume, recording each result onto paper. I disconnected the bung from
the conical flask and then I reset the gas syringe to 0. I emptied the contents
of the conical flask into a container and rinsed the flask with water, drying
it thoroughly with paper towels. I placed the flask on the mat and repeated the
procedure until all the tests were complete. To remain safe while performing the different tests,
I wore safety goggles and an apron when using the hydrochloric acid. I also
ensured careful handling in all parts of testing.To keep the experiment fair throughout, I needed to
ensure the key variables remained constant throughout my experiment. This ensured
my chosen variable of concentration was isolated in the experiment; the results
are then more accurate and direct.For temperature, I realised that in washing the
conical flasks using tap water, the temperature of the flasks would vary
greatly. The first flask would not be washed, meaning it would not cool
significantly like the other flasks. As there were not enough flasks to use a
new one after each test, I washed the first conical flask and tried to get each
conical flask to the same dryness level, using paper towels. Another heat variable comes from moving the conical
flasks, prior to each test; the heat from my hands transfers to the flasks. To
minimise this I handled the conical flasks from the top. This means there is no
heat near the bottom of the flask, where the reaction takes place to affect it. For the key variable of catalysts, I ensured there
would be no necessary interference to the results by not using a catalyst in
any part of my experiment. For surface area, this applies to the marble chips.
I decided there were two factors, the number of chips, and the weight of the
chips. This only applies when the chips are roughly the same size, and means
the surface area will be as even as possible and there is the same amount of
each chip, i.e. density. To do this, for each experiment we used 15 ?medium?
sized chips and weighed each set to be 3.0 grams, using the sensitive digital
scales for the greatest accuracy.To be able to see the changes in each reaction
clearly and compare results, I tested 4 different moles of hydrochloric acid,
0.5, 1.0, 1.5, 2.0. To ensure the greatest degree of accuracy I tested each
mole twice, and then for plotting the results, I took the average for each
point. (Time against volume produced) I also chose to take a third test if the
two sets of results for one mole were significantly different, indicating an
unfair part to the test. I also chose to only time for 3 minutes as this would
be the maximum length of time I could allow due to the time available and
number of tests needing to be performed. This also gave me enough results in
order to see patterns in the graphs and compare more accurately.Other variables I was aware of and accounted for
were:Ø Any product gas escaping
between adding the hydrochloric acid to the marble chips and fitting the bung
in the conical flask. I minimised this by adding the acid at a steady flow each
time, and putting the bung in as soon as all the acid had been poured in. Ø
Shaking the flask to speed up the reaction. As I would
not be able to ensure the level of shaking or heat increase and what the
individual effect on each reaction would be, I decided that for all the tests I
would leave the flask untouched while the reaction took place.Ø
Resetting and checking the apparatus. This included
making sure the gas cylinder was reset fully after each test, and that the
apparatus was sealed properly prior to testing. Predictions:From the above and past scientific knowledge, i.e. a
preliminary experiment, I predict that the higher the concentration of acid,
the faster the rate of reaction. This is due to the concentration of reactants
being proportional to the rate of reaction. This knowledge can be demonstrated
by this example:If there are 100 particles of both reactants, A and
B. There is a certain chance of collisions that could then be successful. If
the particles of each reactant are doubled, the chance of collisions is
doubled. Therefore the rate of reaction is doubled.It is for these reasons that I predict that as
concentration increases, so does the rate of reaction. Prediction graph: Rate of Reaction ????????? ????? ????????????????????????????????????? Concentration I can also calculate the gas produced by the reaction: ???????????????????????????????? Moles?? =? Mass
(g) ?????????????????????????? ??????????????????????????M ????????? ????????????????????????????????????????????? =??? 3.0 ??????????????????????????????????????????????????? 100???????? =0.03 moles of CaCO3???????????????????
1 mole of CaCO3? produces 1 mole CO2????????????????
???Therefore 0.03 moles of CaCO3? produce 0.03 moles of CO2??????????????????????????????? 1 mole occupies 24 dm??????????????????????????????? 0.03 moles = 0.03 X 24?????????????????????????????? = 0.72 dm ????????????????????? ???????????????????
???????????= 720 cm??????????? Preliminary Experiment:To find out whether my method would be the most
suitable to receive accurate results I chose to perform a preliminary
experiment. I chose to use 15 ?medium? chips at 3.0 grams and
use 150ml of hydrochloric acid at 1.0M. ?????????????????????? Results table for
Preliminary Experiment ???????????????????? 1st ????????????????? 2nd ??????????? Average ? Time (seconds) Vol. of gas????????????? produced (cm3 ) ?Time (seconds) Vol. of gas produced
(cm3 ) ?Time (seconds) Vol. of gas produced.
(cm3 ) ?0 ??????????? 0 ??????????? 0???? ?????????? 0 ???????????? 0 ????????
0 10 ??????????? 3 ?????????? 10 ?????????? 5 ??????????? 10 ????????
4 20 ??????????? 5 ?????????? 20 ?????????? 5 ??????????? 20 ????????
5 30 ??????????? 7 ?????????? 30 ?????????? 7 ??????????? 30 ????????
7 40 ??????????? 9 ?????????? 40 ????????? 10 ??????????? 40 ???????
9.5 50 ?????????? 13 ?????????? 50 ????????? 14 ??????????? 50 ??????
13.5 60 ?????????? 18 ?????????? 60 ??????? ??21 ??????????? 60 ??????
19.5 70 ?????????? 25 ?????????? 70 ????????? 29 ??????????? 70 ???????
27 80 ?????????? 32 ?????????? 80 ????????? 34 ??????????? 80 ???????
33 90 ?????????? 39 ?????????? 90 ????????? 41 ??????????? 90 ??????
39.5 ???????? ????100 ?????????? 44 ????????? 100 ????????? 47 ?????????? 100 ??????
45.5 ???????????? 110 ?????????? 52 ????????? 110 ????????? 55 ?????????? 110 ??????
53.5 ???????????? 120 ?????????? 61 ????????? 120 ????????? 63 ?????????? 120 ???????
62 ??????? ?????130 ?????????? 69 ????????? 130 ????????? 71 ?????????? 130 ???????
70 ???????????? 140 ?????????? 77 ????????? 140 ????????? 79 ?????????? 140 ???????
78 ???????????? 150 ?????????? 82 ????????? 150 ????????? 85 ?????????? 150 ??????
83.5 ?????? ??????160 ?????????? 88 ????????? 160 ????????? 92 ?????????? 160 ???????
90 ???????????? 170 ?????????? 94 ????????? 170 ????????? 96 ?????????? 170 ???????
95 ???????????? 180 ?????????? 95 ????????? 180 ????????? 97 ?????????? 180 ???????
96 The experiment worked well and so I did not have to
change anything in the method for the actual testing. Graph ?A? shows the results for my preliminary
experiment and indicates the line of best fit and a straight average trend
line.From my results I could see that as time increased,
so did the gas being produced, indicating that the reaction was taking place
successful.Obtaining Evidence As I have previously mentioned, certain precautions were
taken and ensured throughout testing to certify safety.After recording the results, I needed to be able to
see, and thus understand them clearly in order to make graphs correctly and
accurately. ??????????????????????????????????? Results
table for 0.5M of acid ???????????????????? 1st ????????????????? 2nd ???? ???????Average ? Time (seconds) Vol. of gas????????????? produced (cm3 ) ?Time (seconds) Vol. of gas produced
(cm3 ) ?Time (seconds) Vol. of gas produced.
(cm 3) ?0 ??????????? 0 ??????????? 0???? ?????????? 0 ???????????? 0 ????????? 0 10 ?????????? 3.5 ?????????? 10 ?????????? 3 ??????????? 10 ???????? 3.5 20 ?????????? 3.5 ?????????? 20 ?????????? 3 ??????????? 20 ???????? 3.5 30 ??????????? 4 ?????????? 30 ????????? 3.5 ??????????? 30 ????????? 4 40 ????????? 4.5 ?????????? 40 ?????????? 4 ????? ??????40 ???????? 4.5 50 ??????????? 5 ?????????? 50 ????????? 4.5 ??????????? 50 ????????? 5 60 ??????????? 6 ?????????? 60 ?????????? 5 ??????????? 60 ???????? 5.5 70 ??????????? 7 ?????????? 70 ????????? 5.5 ??????????? 70 ???????? 6.5 80 ????????? ??8 ?????????? 80 ????????? 6.5 ??????????? 80 ???????? 7.5 90 ??????????? 9 ?????????? 90 ??????????? 7 ??????????? 90 ????????? 8 ???????????? 100 ?????????? 10 ????????? 100 ??????????? 8 ?????????? 100 ????????? 9 ???????????? 110 ???????? 11.5 ??? ??????110 ??????????? 9 ?????????? 110 ??????? 10.5 ???????????? 120 ???????? 12.5 ????????? 120 ?????????? 10 ?????????? 120 ??????? 11.5 ???????????? 130 ???????? 13.5 ????????? 130 ?????????? 11 ?????????? 130 ??????? 12.5 ???????????? 140 ????????? 15 ????????? 140 ????????? 12.5 ?????????? 140 ??????? 13.5 ???????????? 150 ?????????? 17 ????????? 150 ?????????? 14 ?????????? 150 ??????? 15.5 ???????????? 160 ?????????? 19 ????????? 160 ?????????? 16 ?????????? 160 ??????? 17.5 ???????????? 170 ? ?????????22 ????????? 170 ?????????? 18 ?????????? 170 ???????? 20 ???????????? 180 ?????????? 25 ????????? 180 ?????????? 21 ?????????? 180 ???????? 23 To do this, I have arranged my results as follows: ??????????????????????????????????? Results
table for 1.0M of acid ???????????????????? 1st ????????????????? 2nd ??????????? Average ? Time (seconds) Vol. of gas????????????? produced (cm3 ) ?Time (seconds) Vol. of gas produced
(cm3 ) ?Time (seconds) Vol. of gas produced.
(cm3 ) ?0 ??????????? 0 ? ??????????0???? ??????????? 0 ???????????? 0 ????????? 0 10 ??????????? 5 ?????????? 10 ??????????? 4 ??????????? 10 ???????? 4.5 20 ??????????? 7 ?????????? 20 ??????????? 6 ??????????? 20 ???????? 6.5 30 ??????????? 9 ?????????? 30 ??????????? 8 ??? ????????30 ???????? 8.5 40 ?????????? 13 ?????????? 40 ?????????? 11 ??????????? 40 ???????? 12 50 ?????????? 15 ?????????? 50 ?????????? 14 ??????????? 50 ??????? 14.5 60 ?????????? 18 ?????????? 60 ?????????? 17 ??????????? 60 ??????? 17.5 70 ?????? ????23 ?????????? 70 ?????????? 22 ??????????? 70 ??????? 22.5 80 ?????????? 28 ?????????? 80 ?????????? 26 ??????????? 80 ???????? 27 90 ?????????? 34 ?????????? 90 ?????????? 32 ??????????? 90 ???????? 33 ???????????? 100 ?????????? 40 ????????? 100 ?????????? 38 ?????????? 100 ???????? 39 ???????????? 110 ?????????? 47 ????????? 110 ?????????? 44 ?????????? 110 ??????? 45.5 ???????????? 120 ?????????? 53 ????????? 120 ?????????? 50 ?????????? 120 ??????? 51.5 ???????????? 130 ?????????? 59 ?????? ???130 ?????????? 57 ?????????? 130 ???????? 58 ???????????? 140 ?????????? 67 ????????? 140 ?????????? 64 ?????????? 140 ??????? 65.5 ???????????? 150 ?????????? 74 ????????? 150 ?????????? 70 ?????????? 150 ???????? 72 ???????????? 160 ?????????? 79 ?????????
160 ?????????? 75 ?????????? 160 ???????? 77 ???????????? 170 ?????????? 84 ????????? 170 ?????????? 80 ?????????? 170 ???????? 82 ???????????? 180 ?????????? 89 ????????? 180 ?????????? 85 ?????????? 180 ???????? 87 ??????????????????????? ????????????Results table for 1.5M of acid ???????????????????? 1st ????????????????? 2nd ??????????? Average ? Time (seconds) Vol. of gas????????????? produced (cm3 ) ?Time (seconds) Vol. of gas produced
(cm3 ) ?Time (seconds) Vol. of gas produced.
(cm3 ) ?0 ??????????? 0 ??????????? 0???? ??????????? 0 ???????????? 0 ????????? 0 10 ??????????? 6 ?????????? 10 ??????????? 5 ??????????? 10 ??????? 5.5 20 ?????????? 10 ?????????? 20 ??????????? 9 ??????????? 20 ??????? 9.5 30 ?????????? 16 ?????????? 30 ?????????? 15 ??????????? 30 ?????? 15.5 40 ?????????? 22 ?????????? 40 ?????????? 21 ??????????? 40 ?????? 21.5 50 ?????????? 31 ?????????? 50 ?????????? 29 ??????????? 50 ??????? 30 60 ?????????? 38 ?????????? 60 ?????????? 36 ??????????? 60 ????? ??37 70 ?????????? 47 ?????????? 70 ?????????? 45 ??????????? 70 ??????? 46 80 ?????????? 57 ?????????? 80 ?????????? 55 ??????????? 80 ??????? 56 90 ?????????? 67 ?????????? 90 ?????????? 65 ??????????? 90 ??????? 66 ???????????? 100 ?????????? 76 ? ????????100 ?????????? 74 ?????????? 100 ??????? 75 ???????????? 110 ?????????? 84 ????????? 110 ?????????? 83 ?????????? 110 ?????? 83.5 ???????????? 120 ?????????? 97 ????????? 120 ?????????? 95 ?????????? 120 ??????? 96 ???????????? 130 ????????? 107 ????????? 130 ????????? 105 ?????????? 130 ?????? 106 ???????????? 140 ????????? 140 ?????????? 140 ???????????? 150 ????????? 150 ?????????? 150 ???????????? 160 ????????? 160 ?????????? 160 ???????????? 170 ????????? 170 ?????????? 170 ???????????? 180 ????????? 180 ?????????? 180 ??????????????????????????????????? Results
table for 2.0M of acid ???????????????????? 1st ????????????????? 2nd ??????????? Average ? Time (seconds) Vol. of gas????????????? produced (cm3 ) ?Time (seconds) Vol. of gas produced