From these theories we can identify what would make the fastest rate of reaction, which would be the concentration of acid and largest surface area which would be the smaller marble chips. Therefore from this I gave decided that I will use the effects of concentration on the smaller marble chips, because both have higher rates of reaction that any other variables.
Below shows what happens during the collision theory with the effects of concentration, the diagrams shows the more particels there are in a higher level of acidic concentration, the more reactions will take place and faster the products are produced.
Diagrams to show the particles reacting in a high concentration level and a low concentration level of hydrochloric acid
(This diagram shows the highest rate of concentration has a faster rate of reaction).
(This diagram above shows a low level of hydrochloric concentration producing a slower rate of reaction).
These diagrams show the comparison between the amounts of concentration in hydrochloric acid, proving that the higher the acidity compared to the diluted solution, the more the particles will react and produce C0 , because there are more particles to collide and react with successfully.
These diagrams also show the setup for a previous preliminary experiment conducted in class about the effects of the collision theory. This experiment is similar to this investigation variable, except it tests the factor of surface area rather than concentration. The class conducted two experiments:
- One testing the rate of which 5g large pieces of calcium carbonate and a fixed variable of 50cm3 hydrochloric acid reacted and how fast over a length of time it produced carbon dioxide.
- The other experiment was using 5g of small marble chips reacting in 50cm3 of hydrochloric acid and recording the amount of carbon dioxide to be produced over a period of time.
These results were compared, showing that the higher surface area from the small chips produced the highest rate of reaction. Here is the table of results for this experiment to show the differences in the large and small chips:
These results occurred because the collision theory suggests that the larger the surface area the more area there is for the particles in the hydrochloric acid to cause molecular collisions with surface of the calcium carbonate. Therefore because the small marble chips had a larger surface area, this meant there was more area for the particles to break the bonds, causing a faster reaction, therefore producing carbon dioxide as a product rapidly compared to the rate of reaction with the large marble chips.
This experiment has helped to plan this investigation because:
- It uses the same reactants of hydrochloric acid and calcium carbonate that I have decided to use for this experiment, and therefore will produce the same products as predicated (see prediction).
- This experiment also allows a design layout of apparatus, because it successfully collects and measures the amount of carbon dioxide being produced, from displacing water out of a cylinder, which is connected to a conical flask where the reaction is taking place. For this investigation, I have decided the design layout of apparatus will recorded the amount of time for 80cm3 of carbon dioxide to displace the water inside the cylinder. This creates a fair test to see how fast in seconds each concentration of hydrochloric acid can produce that certain amount of carbon dioxide as a product, that is reacting with the small pieces of calcium carbonate.
- Scientifically it allows us to view what type of results that might be produced, from using the smaller marble chips. It is already understood that particles will only react when they have enough energy to collide with one another, therefore I will use the largest surface area, because these results show that a faster reaction is gained from the small marble chips. This by allowing a faster reaction in this investigation if the particles have more area to collide with. Also it has been discovered from these results the more there is of one variable the higher the rate of reaction, for example: large surface area, high temperature and more catalyst, will produce a high reaction. Therefore it can be decided that this experiment has helped to plan the prediction because the greater the concentration of acid the higher the rate of reaction, because it will have more particles to react with.
Prediction
From the gathered background knowledge, the results should show the amount of time taken for a certain amount of carbon dioxide to be produced in ascending order, starting with the highest concentration level (see prediction table below). This prediction has been created, because according to the collision theory particales will only react succesfully IF they have enough energy to to collide with one another. This means that a high conentration level in a solution gives more particals in the reaction to react with and collide with one another, meaning a faster reaction, and in this experiment increasing the rate of which carbon dioxide is produced.
Below is a table showing the predictions I have made about this experiment:
Level of Hydrocloric acid Concentration (ml )
100
75 (25ml of distilled water)
50 (50ml of distilled water)
25 (75ml of distilled water)
0 (100ml of distilled water)
Time taken for C0 to be produced (seconds)
20
25
35
45
0
I predict that the higher the concentration the faster the reaction will take place this is because in a higher concentration there will more hydrochloric acid molecules per set volume. 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. However I also think that when there is no acid concentration level, but pure distilled water, there shall be no evident reaction, because it is neutral and does not have a high acidity level, it will not give more particles to the solution and will not cause a fast reaction.
The reaction rate, however, should decrease as the experiment progresses because as the reaction time increases the number of hydrochloric acid molecules present will decrease as they have been reacted to form water calcium chloride and carbon dioxide. The additional water and calcium chloride present as the experiment progresses should decrease the rate of reaction because of decrease in concentration. This should make a graph of the reaction curved as the reaction rate slows down.
The increase in the concentration should be directly proportional to the increase of the reaction rate at a given time. This is because by doubling the number of hydrochloric acid molecules present the chance of a collision should be doubled, as there is now twice the possibility of a collision-taking place initially. This can be thought of as like people in a refined space, if there are twice the number of people there will be twice the chance of people colliding.
The Experiment
The outline of the plan
- We have chosen to investigate how concentration affects the rate of reaction by using an appropriate approach, through the use of previous experiments, accurate measuring, and a good designed layout to collect and produce precise and reliable evidence and results to show how concentration affects a solid or surface area.
- We will make sure our method is safe by following safety procedures carefully
- I have explained what I think will happen in this experiment by using scientific knowledge in my prediction and justified my thoughts.
- To produce reliable evidence by making all measurements as accurate as possible and repeat these experiments.
- 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, which show the highest rate of reaction is gained from higher use of any factor.
The following headings show how the experiment was conducted, apparatus used, what variables remained the same, what measurements were taken to measure the rate of reaction and safety aspects used throughout the experiment:
Measurments
Inputs
These measurements are to ensure the concentration for the hydrochloric acid is accurate and correct and therefore would not interfere with the sets of results gathered from these experiments and make any results anomalous. The following tests below show the amount of hydrochloric acid that will be used to effect the quantity of concentration:
Experiment No. Amount of Hydrochloric acid (ml) Amount of Distilled Water (ml)
1: 100 0
2: 75 25
3: 50 50
4: 25 75
5: 0 100
These experiments will be repeated to gain an average set of results to prevent any anomalies by comparing the results and also they should be in an ascending order of time (seconds) as the concentration of hydrochloric acid decreases.
Outputs
These measurements are the outputs that the reaction will give as products. In these experiments the product should be the amount of carbon dioxide produced in the fastest time, depending on the amount of concentration. The reaction will have to produce 80cm of CO which will be measured by the gas displacing water out of a water filled cylinder which is connected to a side-arm flask where the reaction is taking place. A timer will be used to measure the amount of time the rate of reaction can produce 80cm of CO for each individual concentration.
Fair Test
I am changing the concentration of Hydrochloric acid in my experiment so all other variables must be kept the same, if they are not then they may interfere with my experiment. Certain factors will be difficult to keep the same such as the temperature but as long as the experiment is carried out quickly and during one session I do not think it will effect my results to the point of them being anomalous. To create a fair test in this investigation I will control each experiment by:
- Using the same mass of calcium carbonate (or marble chips) for each concentration worth 5g. This allows all the results to be in relation with one another, otherwise the results will be different than what is expected because if they range in mass, then the marble chips will vary in surface. This means that a higher reaction will occur for more surface area, and will not test the effect of concentration accurately.
- The same size chips will be used as well, instead of varying from large to small marble chips (which can affect the surface area and therefore the highest and lowest rate of reaction results) for each test, the smaller chips will be used, to keep the surface area the same.
- The temperature of each concentrated solution will also have to remain the same, (at room temperature – 22 c) this variable has to remain the same, so that the particles in the solution do not gain extra energy from a higher temperature, and therefore causing more collisions and increasing the rate of reaction. Therefore the initial temperature will be taken before the conduction of each experiment.
- The same amount of carbon dioxide has to be produced from each experiment. Each reaction has to produce exactly 80cm of CO , because this is to measure the rate of reaction fairly and accurately, and to view which concentration can produce this much the fastest.
- I will use the same amount of solution, no matter the acidity of concentration, which will be 100mg, to ensure that each level of concentration to water is accurate and does not alter the acidity of concentration therefore affecting the results.
- If the test tube is not clean then whatever chemical is lining it could affect the outcome of the experiment by changing the reaction. Also I have to make the decision whether I'm going to keep the test tube still or whether I'm going to shake it. This is an important choice, as if I shake one of the test tubes then I'll have to shake all of my experiments. However, I'm choosing to keep the test tube still.
- Repeating the process as many times as I can and get an average by adding them all together and dividing by the number of results I get.
- I will also use the same equipment for each experiment conducted, and making sure the flask and cylinders have been cleaned and dried thoroughly.
The only variable that will change in this experiment is the amount of concentration, which will affect the rate of reaction. For my conclusion to be firm and accurate, my results will have to be reliable and sufficient by making these variables correct. Reliable is not something that I can guarantee, but sufficient is something that I can try to do by using these methods of reliability by controlling measurements and factors. However sometimes the reliability of apparatus can be poor or the chemicals can have been corrupted, this in turn may effect the rate of reaction or accuracy of results and evidence.
Apparatus
The following apparatus and chemicals were set up for this method (see diagram for set-up):
Side arm flask with bung
5g of Small Marble chips (CaCO3)
Amount necessary of Hydrochloric Acid (HCL)
2 Measuring cylinders (100 ml)
One filled to the brim with water
- One filled with a concentration of hydrochloric acid and diluted water if necessary.
- Glass tube
Digital Timer
- Water bath half-filled with water
Digital scale measurer
Diagram to show the setup of appartus
Safety
The following safety precautions have to be proceeded with care throughout the experiments, to ensure that there are no accidents and errors when working in the lab:
- Wear goggles at all times to prevent acid from irritating the eye if it happens to have been transferred by accident. (through fingers e.t.c)
- I will have to check the apparatus for any broken pieces, that way, I can avoid injury to myself or avoid a mistake in my experiment through a leak, for instance through the water bath.
- Do not run with anything in hands around the lab, especially acid, incase of collision will other people, therefore the environment around should be observed of what others are doing also.
- Wash hands before and after the experiment to remove grease and any form of acidic solution. This is to prevent acid from entering the stomach or attack the eye.
- Wear overalls to protect clothing from concentrated solutions.
- Clear up any water or solution spillage quickly encase of further accidents for instance slipping over with objects in hands.
Method
By using the preliminary research, I have devised the following method below which shows the procedure for each experiment that will be conducted:
- Set-up apparatus accordingly and carefully following safety rules.
- Measure the amount of hydrochloric acid (cm ) needed (or diluted water - cm ) for the acidity of the concentration that is being tested. Then measure 5g of small calcium carbonate chips on the measuring weighing scales, and fill the water bath and a 100cm cylinder of water.
- Place the water cylinder over the side-arm flask tube in the water bath, being cautious not to loose any water from the cylinder and make sure there are no air bubbles, to ensure accurate measuring therefore accurate results. Prepare the timer.
- Place the small measured chips inside the side arm flask beaker, and pour in the measured amount of concentration, place the bung securely on the top and start the timer.
- Watch the reaction and measure how much carbon dioxide is being produced by leaving the timer until 80cm of carbon dioxide has been produced, (from it displacing water in the cylinder) and stop the timer exactly, to gain the best possible results.
- Record the results from the timer obtained in seconds and clean up all apparatus for the next experiment.
- Once all experiments have been conducted clear apparatus away.
Obtaining Evidence
Introduction
Once all the experiments had been conducted, I decided to check the results and view the obtained evidence to see if they were accurate enough and the prediction made was accurate when they were compared. If the results looked odd then either the experiment had been set incorrectly or a variable or a piece of apparatus had been altered. I collected sufficient evidence and decided to develop them through repeating and averages, and have recorded an appropriate range of reliable evidence:
I decided to do this by:
- Creating a result table showing all results obtained.
- Create an average between both tests for one experiment.
- Create a graph using those averages processed from both sets of results.
Results Table
By creating several tables I would be able to compare the data obtained, and therefore view any errors from both experiments’ results. The two tables below show and present all the results obtained precise to one second and accurate in cm for each solution, from the first and second set of experiments conducted:
Tables to show the results obtained from the effects of different concentrations on marble chips on the varied rates of reaction.
First Experiment
Second Experiment
I then decided to create a table showing the averages obtained accuratly, that had been processed by using the method of adding the results of both experiments for each indivual set of concentration levels and divided by two, to gain an overall average. This method allows to see any anomlaies in the results and if there is, these results would be shown on the graph created, because the line of best fit would not go through all the points, but be isolated from the line. Below is the table to show the averages gathered:
Table of results to show the set of averages processed from each experiments concentration results.
Graph – Showing the rate of reaction from differnet concentrations
On the next page viewed will be the result graph, to see any anomalies in the averages obtained from both sets of results. The line of best fit will show how fast the rate of reaction occurred, depending on the rate of reaction, if my prediction is correct the line will be a curve and will increase as the concentration gets higher. Along the ‘x’ axis will show the amount of hydrochloric acidity concentration level, and along the ‘y’ axis will show the time in seconds how long the reaction took to displace 80cm of water when producing carbon dioxide.
This graph will show the rate of reaction from the effects of different acidic concentration on marble chips, and records through a different medium the averages obtained, allowing a suitable range of reliable evidence to be viewed and analyzed.
Analysing and considering evidence
Introduction
The evidence obtained shows that the higher the level of acidic concentration the faster the rate of reaction of which a product is produced. My method was conducted successfully as it was proved from the graph, that the highest concentration of 100cm compared to the lowest concentration of 25cm of hydrochloric acid would create a faster rate of reaction in producing carbon dioxide as a product. The pattern of ascending values on the graph proves that my prediction was accurate from the preliminary evidence used in the planning. I stated that as the concentration became stronger the carbon dioxide would be produced at a faster rate and would produce a curved graph.
