I will firstly select the first concentration of acid, which will be the lowest concentration solution, which is 40cm3 acid and 10cm3 water and measure that out.
Place the marble chips in the flask and then as quickly as possible place the acid concentration into the flask and apply the stopper, which is connected to the tube. At the same time that goes on my partner will start the stopwatch.
I will watch the stopwatch for 1 minute then stop the investigation by pulling out the stopper. I can measure the speed of the reaction by how much gas is given off. I am going to measure this in cm3 in a gas syringe.
Now read the gas syringe to see how much gas has actually been given off and then record it in my results table
Here is the table I will follow for my concentrations of acid
Water (cm3) Acid (cm3)
50 0
40 10
30 20
20 30
10 40
Fair Test
To be sure I can rely on my results I will repeat he experiment twice or three times if necessary, because there is chance of inaccurate results for many reasons.
Keep the out side temp the same by using a thermometer as It is important to keep the starting temperatures constant for all the reactions as this can affect the results by giving the particles more energy (and making it faster).
Use the same weight of marble chips so that there is not more marble chips in one of the experiments which will mean there will be more for the acid to reacted with
always keep to the same amount of concentration, which is 50cm3 so that each experiment is fair otherwise if one has more solution then they may be more acid which would result in more reactive particles and an unfair test
Preliminary Experiment
I have carried out a preliminary experiment so that I would have extra information so I would be able to know if my previous plan would succeed in the experiment. Everything that I have described above I have kept the same and have treated it as a fair test. Here are my Results
Water (cm3) Acid (cm3) Gas given off
Exp. 1 exp. 2 exp.3 Av.
50 0 3 3 4 7.3
40 10 7 6 8 15.6
30 20 42 42 40 41.3
20 30 62 61 64 62.3
10 40 100 101 105 102
So from my results I can see that my plan does work and that my results show that the higher the concentration the quicker the reaction. I now have all the information I need to go on and predict what will happen in my actual experiment.
Prediction
When the concentration of acid increases, more gas will be given off faster. I know this, as I will be investigating the effect of concentration on the rate of a reaction. If a solution is made more concentrated, then there are more reactant particles per set volume. This makes collisions between the reactant particles more likely. Therefore there will be more collisions per second and as a consequence, more particles reacting per second. so, the rate of the reaction is increased
I predict that the solution with the high concentration of acid will have a much faster rate of reaction than the weaker solution I have predicted this from my scientific knowledge and the knowledge I gathered from my preliminary experiment. I think that this happened because the more acid in the solution the greater the concentration and there will be more particles colliding and more energy and therefore a faster rate of reaction. The reason I think that the rate of reaction will increase is that the experiment is exothermic, this means that it will give itself more energy and therefore more collisions and faster collisions. Therefore I predict that the rate of reaction will increase with the concentration of the acid solutions
