Find out and observe how factors such as heat or concentration can affect the rate of reaction between two solutions.

      results as there may be some solution left in the beaker which may unbalance  

      the equal amount of solution there should be.

     

4. Again, to keep the amount of the solutions balanced, we will have to wash out

the measuring tubes in which we measured out 40ml of each solution. Also, we will have to make sure that the tubes which we measure out the Hydrochloric acid and the Sodium Thiosulphate should be kept separate and not be swapped or mixed up as if we first measure out Hydrochloric acid in a tube then measure out Sodium Thiosulphate in the same tube, a reaction may take place inside the tube as access or left over drops of Hydrochloric acid will react with the sodium Thiosulphate even before we start to time the reaction in the beaker.

 

5. The person with the stopwatch, timing the reaction by pressing the start and  

     stop button will have to stay the same as well. This is because, different people in the group may have different reflexes or may have slower or faster reactions to sound, in this case, the word GO said by the person watching the reaction from the top.

6)  Another factor that can affect the rate of reaction is heat or temperature. This will also, be have to kept the same each time we do the experiment. The temperature of both solutions.

   

I predict that the temperature and the concentration will affect the rate of reaction between the Hydrochloric acid and the Sodium Thiosulphate. Temperature, meaning heat, is a factor known in many other reactions as well, for speeding up the reaction.

For example, the reaction of ice melting, and the more heat there is, the faster the reaction. I think, the warmer the solutions will be, the faster the reaction will take place between the Hydrochloric acid and Sodium Thiosulphate.

The concentration of the solutions is also another main factor that is likely to have affect on the rate of reaction. Therefore I predict that the lower the concentration of any of the solutions, the slower they will react. The higher and stronger the concentration of the solutions, the faster they will react. This is because, the higher the concentration, the denser the solution will be. This means there are more molecules in the solution to react as they will be hitting and colliding with each other more frequently and quicker, where as if the concentration is low, then there are less molecules and there will be less collision taking place.    

                                                   

We will be investigating what are the factors that affect the rates of reaction. We will use Sodium Thiosulphate and Hydrochloric acid to experiment with. There are a few key factors I am going to take into consideration before I under go the investigation. The first consideration is the temperature of the reactants, because when the temperature of the reactants increases, the rate in which the particles move also increases. Meaning the faster the particles move the more collisions being produced by both particles causing a faster rate of reaction. Thus proving the collision theory. The second key factor I am going to take into consideration is the concentration of the Sodium Thiosulphate, because a higher concentration of the sodium Thiosulphate will cause more particles to be produced, causing more particles to be involved in the reaction causing more collisions in which may cause a faster or slower reaction.

To test how the first factor, the temperature of the reactants, affects the reactions we used Hydrochloric acid. Each time we did the experiment, we heated the Hydrochloric acid to different temperatures, but we used the same volume of it every time to keep it a fair test. We used Hydrochloric acid, which was 50 degrees, the warmest, and we mixed it with 40 ml of Sodium Thiosulphate in a beaker that was placed on top of a white mat. The mat was white because it made it easier to view the black cross that was also under the beaker and we had to look at it through the top of the solution as it reacted. We also used a stopwatch to time how long the black cross was visible for through the solution as it reacted and turned cloudier, into a yellowy colour, until the cross was no longer visible. This also meant that the solutions had properly and fully reacted.  

Each time, we used a measuring tube to measure out 40 ml of hydrochloric acid and then we heated it to a certain temperature (50 degrees, 45 degrees, 40 degrees). Then we measured out 40 ml of Sodium thiosulphate and poured in both solutions into a beaker and watched and observed them while they reacted.

Here are the results:-

By doing this, I have found out that a reasonable temperature of HCl to use is approximately room temperature, between 20-30 degrees because the reaction takes place at a reasonable pace. It doesn’t take place too fast (3.7 seconds, at 50 degrees) which is too fast for us to observe properly, or it doesn’t take place too slow (8.54 seconds, at 5 degrees) at this rate we might be waiting all day. Also, this will make it a fair test, as the acid will be at the same temperature each time, without us having to heat or cool the acid. The temperature will come naturally.

The other thing we experimented with was the amount of HCL and Sodium Thiosulphate we should use, as in the volume. We decided in the end that 40 ml was the best amount of each solution to use. We did a number of tests with different volumes of solutions because this would tell us how much we should actually use in our final exam, mainly, it would keep the whole experiment more fair. First we measured out 5 ml of both Hydrochloric acid and Sodium Thiosulphate. Then we mixed them together in a beaker and timed the reaction with a stopwatch. We found out that we needed to increase the amount of both the solutions as the reaction of such a little amount of solutions was too quick for us to observe properly. So we increased the amount of both solutions by 5 ml and we repeated the experiment and timed how long the black cross under the beaker is visible for. We continuously repeated this experiment, trying to find just the right amount of solutions to use that would give us reliable results, and that wont react too fast or too slow.

Here are the results-    

We came to the decision that we would use 40 ml of Hydrochloric acid and Sodium Thiosulphate. This is because, we thought that if we use 5 ml of each, the reaction will take too long and we only have one science lesson to carry out the experiment within. Also, according to a shared opinion, we thought that 5 ml is an amount too little and difficult to measure out. As we increased the volume, we noticed that the time for the reaction to take place decreased. The last or highest volume we tested was 50 ml as the time of reaction was getting slightly too quick for us to observe.

Also, 50 ml of hydrochloric was more than enough to do a single test with, as we would be then using 50 ml each time. This would be a waste of solution. We looked back at our results and thought that 40 ml was a reasonable amount of solution to use as the time of reaction wasn’t’ too slow or quick to time, we were comfortable with it. This amount is also easier to measure out. We wouldn’t go too much over or pour out too less while measuring out this amount, which also saved time.      

1. 1080 ml of Hydrochloric acid
2. 540 ml of Sodium Thiosulphate
3. 540 ml of water
4. A white safety mat
5. A black laminated cross
6. 2 measuring cylinders
7. A stopwatch
8. Goggles
9. A beaker

     10) A pipette

1. Place a white mat on the table with a black cross on it. Then place a beaker on top of them both which will be used to pour in the solutions so they can react.

2. Measure out 40 ml of Hydrochloric acid and 40 ml of Sodium Thiosulphate in      

            measuring tubes.

     

3. Have one person holding a stopwatch ready to time the reaction, have another    

person who will be pouring in the solutions in to the beaker either one at a  

time or together and have a last person overlooking the beaker ready to say  

      stop as soon as the black cross is no longer visible to him.  

4. Pour in the solutions from each tube into the beaker, and as accurately as  

possible, time the reaction between the two. Record the time it takes to react or the black cross underneath to disappear.

5. Repeat this experiment, the reaction between 40 ml of Hydrochloric acid and  

     40 ml of Sodium Thiosulphate. At the least, do it thrice, and then record the  

     time of each reaction. Record this data in a table and then work out an average        

     time of reaction by using the results you get.

6. Next, before doing the experiment, make sure the beaker you used has been    

      washed out and dried or has been changed. Then place the beaker back on the  

      cross ready to do the next test.

7. For the next test, you will need to measure out 40 ml of hydrochloric acid in  

      the same tube you used before but only 35 ml of Sodium Thiosulphate as you

      will be mixing it with 5 ml of water.

8. Have each person ready to time, pour in the solutions and to watch the  

reaction, ready to do the next set of tests. You will have to do this test the same number of times you did the previous tests.

9. For the next tests, again measure out 40 ml of Hydrochloric acid and now only  

      30 ml of Sodium Thiosulphate and mix it with 10 ml of water. Do the test 3    

      times again and record the results in the table and work out the average time of  

      reaction. Make sure to keep washing out or changing the beaker between  

      every test.

10.  Carry on the experiment by reducing the amount of Sodium Thiosulphate  

       each time by 5 ml and increasing the amount of water you mix with it by 5 ml

       each time as well. (25ml Sodium Thiosulphate with 15ml water, then 20ml  

       Sodium Thiosulphate with 20ml water and so on all the way until the test is

       done with 40ml Hydrochloric acid and 40ml water)  

Here are the final results for the concentration experiment:

After carrying out and completing the experiment successfully, my results show that both, the factors of heat and concentration, affect the rate of reaction between Hydrochloric acid and Sodium Thiosulphate. The heat factor, in any case, whether it is the Hydrochloric acid or the Sodium Thiosulphate that is heated, will increase the speed of the reaction. Also the more it is heated, the faster the reaction will take place.  

My results also show us that the concentration of any solution can also have a great affect on the rate of reaction. When we completed the experiment, we found out that the lower the concentration is, the slower the reaction will take place because as we can see in the table of our results, the reaction takes place in about 4.5 seconds when the concentrations are at their highest. (40ml of Hydrochloric acid and 40ml of Sodium Thiosulphate). When the concentration of the Sodium Thiosulphate is about half of this (40ml of Hydrochloric acid, 20ml of Sodium Thiosulphate mixed with 20ml of water), we could see that the time of reaction increased, meaning took longer to react, to approx. 16 seconds.

This supports my prediction because I predicted that, the concentration would have had an affect on the time the solutions take to react. The higher the concentration, the faster the reaction will take place. We have clearly seen this. My prediction followed the collision theory. This theory tells us that the more particles there are in a certain amount of space, the quicker and more often the particles will collide with each other and will react whereas if there are less particles in the same amount of space, there will be less collisions and les reaction.

                                                                                   

                                                                                       

                               

                               

           

           

I think that over all this experiment went well and was successful as it gave us some clear and reliable results. It showed us how some factors can affect the rate of reaction so it helped us to achieve our aim. All of our variables such as the temperature and the concentration were controlled. The main variable we tested and used was concentration. We changed this variable by 5ml every time to slowly reduce the concentration. This was measured out as accurately as possible every time we did the test. Some arts of the experiment could have gone better.

We may have made mistakes while carrying out some of the tasks, such as measuring out the solutions for the experiment or timing the experiment because the stopwatch cannot be 100% accurate as it is manual and is controlled by a person. Also the person viewing the reaction could have made the mistake as the human eye can also make errors. If we had the equipment, we could remove the human eye errors by using light sensors to detect when the black cross is no longer visible. This can be used in conjunction with a timer, for example the conical flask could be connected to a light detector and a timer. The light sensors will detect when there is no light shining through the substance, this will automatically stop the timer, therefore this will give me a better and more accurate result also this will make it a fairer test to time the reaction as they can be 100% accurate and not have to got through 2 people, one co-ordinating and the other timing, which can affect the experiment.

We could have made our experiment even more accurate by doing various things such as spending more time doing the experiment. This is because then we wouldn’t be racing against the time factor and would have been able to take our time to measure out the solutions as accurately as possible and not measure too less or measure out too much in a hurry, which may disturb the pattern in our results.  

If I were to do this experiment again, I would spend more time doing the experiment and make sure all the solutions are measured out as accurately as possible before the experiment. I would also use a light sensor to measure the rates of the reactions because this would make our results 100 % accurate and we would be able to see the pattern of the affect clearly.