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Science Investigation Essay Research Paper Science (стр. 1 из 2)

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

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