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

(cm3 ) ?Time (seconds) Vol. of gas produced.

(cm3 ) ?0 ?????????? 0 ??????????? 0???? ?????????? 0 ???????????? 0 ????????? 0 10 ?????????? 7 ?????????? 10 ?????????? 9 ??????????? 10 ????????? 8 20 ????????? 12 ?????????? 20 ????????? 14 ??????????? 20 ???????? 13 30 ????????? 19 ?????????? 30 ????????? 22 ??????????? 30 ???????? 21 40 ????????? 26 ?????????? 40 ????????? 30 ??????????? 40 ???????? 28 50 ????????? 36 ?????????? 50 ????????? 37 ??????????? 50 ??????? 36.5 60 ????????? 48 ?????????? 60 ????????? 50 ??????????? 60 ???????? 49 70 ????????? 57 ?????????? 70 ????????? 58 ??????????? 70 ??????? 57.5 80 ????????? 68 ?????????? 80 ????????? 64 ??????????? 80 ??????? 65.5 90 ????????? 76 ?????????? 90 ??????? ??79 ??????????? 90 ???????? 78 ???????????? 100 ????????? 90 ????????? 100 ????????? 90 ?????????? 100 ???????? 90 ???????????? 110 ???????? 103 ????????? 110 ???????? 105 ?????????? 110 ??????? 104 ???????????? 120 ????????? 120 ?????????? 120 ?? ??????????130 ????????? 130 ?????????? 130 ???????????? 140 ????????? 140 ?????????? 140 ???????????? 150 ????????? 150 ?????????? 150 ???????????? 160 ????????? 160 ?????????? 160 ???????????? 170 ????????? 170 ?????????? 170 ???????? ????180 ????????? 180 ?????????? 180 Observations:When I reacted the marble chips with the

hydrochloric acid, I observed different effects taking place. In the first

instant that the two reactants made contact, I observed nothing occur. However once

the acid had settled inside the flask a second later fizzing began to occur,

producing bubbles that rose to the surface in a whitish mix, after travelling

upward through the acid while some bubbles that formed, stayed on the marble

chips for longer.? As this bubbling

occurred, there was an audible ?fizzing? sound I detected directly from where

the reaction was occurring. I did not observe a colour change different to the

marble chips, nor did I notice a visible gas rising through the already present

air in the flask.Graph ?B? shows the lines of best fit for the four

different concentrations of Hydrochloric acid.Graph

?C? shows the straight trend lines for the four different concentrations of

Hydrochloric acid.Rates

of reactions:To find out whether my predictions are correct, I need to

directly compare the concentration of Hydrochloric acid with the rates of

reaction on a graph. From this I can then make a straight trend line that will

clearly show me what the trend in my results are.To

find the different rates of reaction I divide the increase of gas by the time

in seconds for each Mole of Hydrochloric acid.0.5

= 23 ??????? 180?

=? 0.127 Concentration Rate ????????? 0.5 ???? 0.127 ????????? 1.0 ???? 0.483 ????????? 1.5 0.815384165 ??? ??????2.0 ?????? 0.9 1.0

= 87 ??????? 180?

=? 0.483?? 1.5

= 106 130

=? 0.8153846152.0

= 90 ??????? 100?

=? 0.9 Graph ?D? shows the trend line for concentration of Hydrochloric acid

against the rates of reaction.Analysing:From looking at graph B, I can see my results by looking at the line of

best fit. As time increases so does the volume of gas produced.? For all the moles of acid this increase

starts gradually before then building up to create a steeper part of the curve.

For 1.0M of acid, I can also see this curve begin to fall towards the

horizontal indicating that the gas produced is now decreasing. As for Moles 1.5

and 2.0 of acid, I can see the same pattern where the curve is steepest at

about half way through the test (90s). I expect that if the time were increased

for these two tests, I would see the same drop toward the horizontal. For 0.5M

of acid, the entire pattern is there, but as the results are only deviated a

little it is difficult to see clearly. From looking at graph ?C?, I can clearly see how different the results are

from each other as it shows a straight trend line for each M of acid. The

greatest difference can be seen between 0.5 and 1.0M, the second largest was

between 1.0 and 1.5 and the smallest difference was between 1.5 and 2.0M of

acid. I can also see that there is a pattern at the start of each test.Graph

?E? shows the graph for 1.0M of Hydrochloric acid.In Graph ?E? I have chosen to use a line of best fit as I

can see how some points are not in sync with it. I have also chosen to use 1.0M

of acid to demonstrate a pattern, as it is most prominent in these results. I

noticed that for each set of results, the first point on each line was above

the lines of best fit as indicated.? I realised

that this was occurring when I placed the bung in the conical flask. As I did

this, the air inside the conical flask would of compressed thus pushing air

through the connection tube into the gas syringe. The amount of increase in the

syringe would then be varied as the amount the bung was pushed in.From looking at graph ?D? I can see how concentration

affects the rate of reaction directly by use of a straight trend line. It is

clearly obvious that the rate of reaction is directly proportional to

concentration. Predictions:As I predicted in a statement and a graph, the rate of

reaction is directly proportional to the concentration. This is seen from graph

?D?, where each point for concentration is higher for the rate of reaction than

the previous. Again indicated by the straight trend line that shows positive

correlation. Conclusion:My prediction is correct because the concentration of

reactants is a critical factor that affects the rate of a reaction. This can be

explained by understanding how reactions occur and how different factors affect

them.For reactions to occur, particles must collide with a

sufficient force. The concentration of a reactant determines how many particles

of that particular reactant will be in a solution. If you increase the

concentration, thus increasing the number of reactant particles, then

collisions are more likely to occur. This can be demonstrated clearly by the

diagram below:If you increase the number of collisions between the

particles of reactants, you will consequently increase the rate of reaction.I can also demonstrate this by my rate of reaction

results:1.0M is half of 2.0M of Hydrochloric acid So the rate of reaction for 1.0M should be half the rate

of reaction for 2.0M of Hydrochloric acid1.0M = 0.4832.0M = 0.9As you can see, the rate of reaction is near to doubled,

from 1.0M to 2.0M Evaluation: For this investigation, I found repeated results were

similar to the first, indicating a good method with no substantial mistakes. I

also found my results to be similar to some other people?s, while exceeding the

standard of others. To have fair results in this investigation I needed to

ensure several factors remained constant throughout testing. However I can only

attain a level of accuracy depending on how fair my testing is. I feel, for the

equipment and materials we were allowed to use, I achieved a high standard of

accuracy that gave me excellent results with minimal anomalies.Here I will list the factors that may be the cause for

slight inaccuracies in my experiment. This will show how anomalies can be

accounted for:·

Scales not correctly read or set, giving different

measurements of calcium carbonate.·

Variations in pouring Hydrochloric acid, more or less

agitation of the marble chips, varying surface area.·

Arrangement of chips when placed in flask, varying

surface area for acid.·

Friction in the gas syringe moving at a minimal

pressure, i.e. not smoothly.·

Displacement of gas when inserting bung into flask.·

Calcium carbonate dust that is weighed and then not

used in the reaction.·

Marble chips not of equal surface area.·

Differences in water left from washing the conical

flask after each test.The only way a completely fair test could occur with the

most accurate results, would be to follow the following factors and to account

for the previous ones.§

A completely sterile and constant laboratory

environment. §

Exact Hydrochloric acid volumes or larger quantities of

acid and marble chips i.e. 500ml of acid and 10 grams of calcium carbonate thus

reducing surface area as a factor.? §

Exact chip number, weight and surface area. §

Pure Calcium Carbonate. §

Allow all of the reaction to occur irrespective of

time. §

Take an infinite number of tests and average exactly. &sect