Investigate how concentration affects the rate of reaction we will be reacting calcium carbonate and hydrochloric acid.

Conical Flask with a bung and Delivery Tube: The bung with a delivery tube will be taken out as calcium carbonate and hydrochloric acid are added. As soon as the second substance is added and the variable (which in my experiment will be temperature) is controlled the bung must be placed back into the flask as soon as possible, thus ensuring that all carbon dioxide produced is collected in the water filled test tube being held up inside the water tray. The delivery tube must be inside the test tube, as then all carbon dioxide produced will rise up inside the test tube (This ensures that the results are correct and as precise as possible). This is a very good way to carry out the experiment as all carbon dioxide produced at different temperatures will be captured in the test tube and will be measured by how long it takes for 20cm³ of carbon dioxide to be produced. Burettes will be used to measure out precisely 20ml of acid for each experiment.

How to use a burette:

. Attach the Burette to a clamp stand

2. Make sure the tap is closed before adding a substance

3. Wear goggles

4. Fill the Burette using a funnel (Lift the funnel slightly so a vacuum is not created)

5. Fill the Burette at eye level so you do not hold acids etc above eye height as this is dangerous

6. Fill the burette to 0 on the scale

7. Place a beaker/test tube/substance holder under the Burette

8. Open the tap

9. Swirl the Beaker etc, until the reaction has occurred

0. Turn the tap off

1. Record the new reading on the scale

Scientific knowledge:

Reference: Ronald W. Armstrong (University of Maryland)

The thermal activation theory of Eyring (H. Eyring, J. Chem. Phys.) 4, 283 (1936), which, in his words, describes the rates of processes in which matter rearranges itself in surmounting a potential barrier, leads, as is well known, to a definition of a function of temperature and stress, the so-called volume of thermal activation, in terms of the rate of change of stress with respect to the logarithm of strain rate at constant temperature. Applying this relation to the yield stress of polymethylmethacrylate at various temperatures and strain rates as measured by Bauwens-Crowet(C. Bauwens-Crowet, J. Mater. Sci.) 8, 968 (1973). Shows that its yield stress may reasonably well be described by a thermal activation equation in which the volume of activation is inversely proportional to the yield stress. The thermal activation equation has also been applied to describe the dynamic elastic and plastic stress-strain behavior of polytetrafluoroethylene as a function of temperature, strain rate, and pressure (F. J. Zerilli and R. W. Armstrong, submitted to J. Appl. Phys.).

Prediction:

I predict that the higher the temperature the faster the reaction will take place this is because with a higher temperature the enzymes will be moving faster as the heat is changed into kinetic energy. This means that there will be a higher chance of the calcium carbonate molecules colliding with the hydrochloric acid and reacting. This should in theory increase the rate of reaction as the concentration is increased.

Activation energy should not be changed in this experiment though as the same amount energy will be required to break the bonds. This is because each particle has the same amount of energy the only reason the reaction is faster is because the particles are moving faster. This means activation energy will not have an effect on this experiment.

Variables

The variables that may have an affect on this experiment is: Size of marble chip- the size of the marble chip will affect our experiment because this dictates the surface area. The larger the surface area the higher the amount of acid in contact with the marble chips. This will allow more acid to react.

Concentration of hydrochloric acid- this is the proportion of hydrochloric acid in the solution.

Volume of acid- this will be the amount of hydrochloric acid that will be reacted with the marble chips.

Catalysts- by weakening bonds this increases the rate of reaction by lowering activation energy a catalyst will not be used in this reaction, however.

Mass of marble chips- the mass of the marble chips is a way of measuring the quantity of chips being used.

Temperature- the temperature adds energy to the reaction an affects how quickly the particles move. By doing this temperature affects the number of affective collisions. This is the variable being measured in this experiment.

Light intensity- the light intensity has a very small affect on the experiment so will not be measured in this experiment.

Outline Plan

We have chosen to investigate how temperature affects the rate of reaction

We will make sure our method is safe by wearing safety goggles and following safety procedures carefully

I have explained what I think will happen in this experiment by using scientific knowledge in my prediction

To make this a fair test I will control the variables I am not investigating and to find these values I have carried out preliminary experiments.

Safety

To make sure we are safe in the lab here are some of the things we will do in more detail.

Wear safety goggles because we are dealing with acids

Tuck stools in to make sure no one falls in the lab

Never run in the lab

Always stand up when carrying out experiments so we can move away if we are in any danger

When carrying out a titration always pour acid into the burette below eye level so that you are not holding acid above your head, as this is dangerous.

Obtaining evidence

While working all safety procedures were followed very carefully like the use of safety goggles and putting the bags under the table. The measurements I feel were fairly accurate as the results were what was expected. There was one anomalous result, however, which was repeated to get a more accurate result. We repeated the experiment three times so we could find averages and get more accurate results. The results were measured to the nearest centimetre cubed because this was the maximum accuracy of the cylinders. The results show the results we got for each experiment.

Results (first experiment)

Temperature

Time (Seconds)

0

63

20

40

30

30

40

21

50

5

60

0

70

6

Results (second experiment)

Temperature

Time (Seconds)

0

60

20

42

30

32

40

23

50

6

60

9

70

7

Mean results for both experiments:

Temperature

Time (Seconds)

0

61.5

20

41

30

31

40

22

50

5.5

60

9.5

70

6.5

Analysis and Conclusions

From these results we can conclude that by increasing the temperature the reaction rate is increased. This can be seen as the highest temperature had the highest reaction rate, a mean time of 6.5 where as the lowest temperature took 61.5 seconds to produce 20cm³ of carbon dioxide. The increase does seem to be proportional, as the gradient of the line seems to decrease by roughly the same amount each time.

The results that were found were what were expected to a certain degree. The reaction rate did not seem to show any signs of slowing down though which is what was expected.

The fact that the reaction rate was highest at the highest temperatures shows that the higher the temperature the faster the rate of reaction. This also proves tat activation energy does not play a part because if this did the gradients of the lines would not decrease by the amounts they did.

It was interesting to see that no enzymes became denatured in this experiment, as this would have caused temperatures above roughly 50 degrees to have slower times and the graphs produced would have shown a curve if that was the case.

Evaluation

The results that were derived from the experiments showed a pattern but and the prediction that was made was supported well by the results obtained. The temperatures were accurate to roughly within one degree of the temperature marked down allowing for either human error or a fault with the thermometer.

The method did show the relationship between the temperature and the rate of reaction but there was a slight margin of error because when turning the cylinder upside down a small volume of water was lost. To solve this problem we could use a gas syringe but the problem with this is we could not test the higher volumes of gas, which would mean the range of results would be lower which would mean the pattern we got would be less obvious. The other problem with using a gas syringe as found in the preliminary experiment was the reaction took place too quickly and there was a risk of the gas syringe breaking.

The experiments were fair tests to a certain extent but there was a certain margin of error because the measuring cylinder when turned upside down in the water tray lost some of the water held within it. Also the values of the controlled variables were not exact amounts so the may have been slightly differently each time which would have affected slightly the reliability of the results. This would have made little difference to the results.

To find if the prediction was supported or to find if the reaction rate did slow down at certain temperatures the experiment could be extended, for instance measuring for more than 20cm³ of carbon dioxide and investigating different temperatures for example above 70 degrees or below 10 degrees. More precise temperatures could also be measured for instance only going up by two degrees at a time instead of ten. This would also enable us to find weather the pattern changed after a certain time or the reaction rate just generally slowed down and we found a curve when comparing the temperature and the calcium carbonate.

Niall O'Connor Page 1 5/17/2007