We recorded the results,
We decided that the temperature would be very difficult to do accurately because it is very hard to measure the temperature exactly. Also it is very hard to keep the temperature at the same level during the experiment, as heat will obviously be given off and therefore cool down. This cooling down will have an affect on the particles colliding and therefore less acid will react with the indigestion tablet, obviously affecting the rate at which carbon dioxide is given off.
We therefore chose to try out concentration. We planned a basic experiment, which could be developed on if used as a final experiment. We varied the concentration from with in a select range to see the effects from 20% to 60%. We thought we should concentrate in between 20% – 60% as this spacing between each concentration can be constant and it allows us to look at a broad range of concentrations, (low – quite high).
- We took 5 different beakers and filled then with different shares of acid to water to vary the concentration by measuring the different quantities of acid in a measuring cylinder. This was then mixed to a certain quantity of water to produce 50 cmCUBED of the acid (5 beakers in different concentrations). We used half tablets and made the acid and water add up to 50 cmCUBED**
to reduce the amount of carbon dioxide given off so it could be collected by a measuring cylinder.
-We poured each beaker into a different chonical flask and added the amount of water needed to get 5 sets of different concentrations.
-A bowl was the filled with water and a bung connected to a delivery tube was held over the chonical flask. The end of the delivery tube was then placed under the bowls water.
-A measuring cylinder was then filled to its maximum capacity with water. It was then covered by hand and tipped upside down and placed under the bowl’s water, the water all remains in the tube and allowed us to measure the gas given off.
-The tablet was dropped in an immediately we sealed the bung onto the chonical flask. At the same time a stopwatch was started to record the time taken. When all signs of the carbon dioxide being given had stopped (no more fizzing and the tablet being no-longer visible in solution) we stopped timing and then recorded our results.
*concemtration prelim table of results
We decided that we should use concentration because the preliminary experiment worked well and so with improvements to the equipment we would be able to produce some accurate results. The changes we decided we wanted to the equipment were to:
- Change tap water to distilled water for experiment.
- Instead of half tablet use a whole one (otherwise surface area may vary per tablet die to cut in tablet).
- Use a burette not a measuring cylinder to measure out the different quantities of acid and water.
- Make sure no stirring takes place in any experiments as this will increase the rate of reaction due to the ‘collision theory’. This would be ok to do however, there is no way to ensure that you have stirred the each conical flask the same – making it an unfair test.
Variables,
Concentration,
The variable I am going to vary is concentration; the advantage of this is it can be varied accurately by simply adding water. However, there are also other variables as well that will affect the experiment if not considered.
With a higher concentration there is more particles per volume of substance. This means the more concentrated the acid is, the more particles there are ready to collide with the tablet particles (which are the same in all experiment). This means that as the concentration is raised the more particles there are that are free to react. If there is more particles than the other subject not all the particles will be used up and it will mean there will be less distance to find a particle it wants to react with, therefore being quicker.
Temperature,
When the temperature is increased the particles in the newly made solution will collide a lot quicker. This means that more reactions will happen quicker because when different particles collide together they react (depending on the strength of collision) this is called the ‘collision theory’.
Size of substance (surface area),
The surface area of the indigestion tablet is very important because if it is in one large piece the places that particles can collide will only be reachable at the sides, not in the inside. This means that for the acid particles to collide with the tablet, the side of the tablet has to react first before the layer underneath can. This really affects the rate of reaction and so must be controlled.
Catalysts,
A catalyst provides a surface for the particles to stick to and therefore come into contact with more particles to react with. This speeds up the rate of reaction however I shall not use any catalysts in my experiment.
Prediction,
We can predict what will happed because of the collision theory. The collision theory means that as the concentration is varied higher for the acid, more collisions will take place; this means that the rate of reaction will be higher. I think that as you increase the concentration more particles will be contained in the same volume of solution. This means that there will be more acid particles to indigestion tablet particles, so the particles will have to travel shorter distance to collide and will be easier to find.
I predict that at the beginning of the experiment (at 20%) there may not actually be enough acid to react with all the tablet and if there is enough it will be in the same volume of the others, so particles will have to travel further to collide as the particles are more spread out in the solution. However, if you take a more concentrated acid like 60% then there will be more particles in the same volume of acid. This means there may be a left over amount of particles after the acid and indigestion tablet has reacted. It also means that the particles will have to travel less far and it will be easier to find another particle to react with therefore making the rate of reaction faster.
Although very hard to predict the actual rate of the reaction it is not too hard to predict the gradient of a graph produced from this type of experiment.
Method,
