The following methods of increasing the rate of reaction can be explained by increasing the number of collisions between the reacting particles:
Sandeep Brar 10D2
- Temperature- When the temperature is increased in a reaction the particles begin to move around much quicker. This means that when they collide with each other they will collide harder.
- Catalyst- A catalyst works by giving the reacting particles a surface to stick to on which they can collide with each other on. This also increases the number of collisions between the particles.
- Size- If one of the reactants is a solid it will have a smaller surface area than a solid that is broken up into smaller pieces. This allows the particles in the solution to have a bigger area to collide in.
- Concentration- A more concentrated solution means there are more reactant particles moving about amongst the water particles. This makes collisions between the reactant particles more likely.
*In order to make my investigation results more reliable I controlled a number of different factors:
1) I must keep the temperature the same because if I allow the temperature to change I will also be increasing the rate of reaction. I must control the temperature throughout the entire investigation.
2) I must control the concentration of Hydrochloric acid being used in my investigation because if the concentration were changed the rate of reaction will also be affected. I will use the same concentration of Hydrochloric acid throughout the whole investigation.
3) If the volume of Sodium Thiosulphate being used was changed in the middle of the investigation then the rate of reaction will be affected.
Variables:
The concentration of Sodium Thiosulphate will be changed throughout the investigation and this makes it the independent variable in my investigation.
In my investigation the dependent variable will be the time it takes for the reaction between Sodium Thiosulphate and Hydrochloric acid to take place. This is because for the final result the time depends on the Sodium Thiosulphate concentration.
This diagram shows that if no collision occurs between the reactant particles then there is no reaction at all.
Sandeep Brar 10D2
This diagram shows a Hydrochloric acid particle and Sodium Thiosulphate particles colliding with one another. So if there is a collision between the reactant particles then it is likely that a reaction will soon follow between the two reactants.
Apparatus:
- Sodium Thiosulphate (varying concentrations)
- Hydrochloric acid
- measuring cylinder
- beaker
- Stopwatch
- glass rod
- Test Tube
- Black marker- to mark cross on measuring cylinder
- Goggles
- Lab coat
- 100ml water
- Burette
- Thermometer
- Pipette
*In this investigation I used a burette instead of a conical flask because I think a burette is more accurate than a conical flask.
Method:
- Collect all the apparatus listed in the apparatus list above.
- Set up all the apparatus as shown in the diagram below.
- Put on all protective clothing required-goggles and lab coat.
- Draw a medium sized black dot with a black marker on the test tube.
- Pour a 100ml of water into the beaker.
- Pour any concentration of Sodium Thiosulphate into the measuring cylinder.
- Pour 5ml Hydrochloric acid into the test tube.
- Carefully put the test tube containing Hydrochloric acid into the beaker and check that the black dot is not facing you. The black dot should be facing away from you.
- Carefully pour the Sodium Thiosulphate from the measuring cylinder into the test tube which should be placed inside the beaker containing 100ml of water.
- As soon as the Sodium Thiosulphate is poured into the test tube containing the Hydrochloric acid start the stopwatch. Stir the liquid in the test tube with the glass rod once or twice.
- Keep looking at the black dot you drew onto the test tube. Remember, the black dot should be facing away from you.
- Once you can no longer see the black dot through the test tube you have to stop your stop
watch.
Sandeep Brar 10D2
- The liquid in the test tube should have become too murky to allow the black dot to be seen through it. This would inform you that the reaction between the Sodium Thiosulphate and the Hydrochloric acid has been completed.
- The time you have on your stopwatch is the reaction time. To get the rate of reaction divide one by the number displayed on your stopwatch.
- Write down your reaction time, rate of reaction and the concentration of Sodium Thiosulphate you used for that reaction in a results table.
- Repeat the investigation until you have repeated it eight times in total. Each time you repeat the investigation you should use a different Sodium Thiosulphate concentration. After every investigation involving one concentration of Sodium Thiosulphate you must thoroughly wash the test tube to avoid any preliminary reactions occurring. Throughout the whole investigation the amount of Hydrochloric acid you use should remain at 5ml per reaction investigation.
Diagram:
Results Table:
Conclusion:
Once I had obtained all my results and completed my investigation successfully I came to the conclusion that my prediction was correct. After completing my investigation I came to the conclusion that as the concentration of Sodium Thiosulphate increases then the rate of reaction will also increase in proportion to the Sodium Thiosulphate concentration. In my investigation no anomalous results were present. The graph which I drew was based on the results I got from this investigation and once I had plotted the points and drawn a line of best fit I noticed that none of the
Sandeep Brar 10D2
points were far off from the best fit line and this suggests that I carried out my investigation successfully and that my results appeared and were correct.
Evaluation:
In this investigation I think I worked well as I was able to understand how to set-up and carry out the investigation quickly with ease. I think that none of the results that I obtained have been anomalous and this suggests that my results were all correct and that I carried out the investigation correctly. I was also able to understand why substances react with one another. This was partly due to my own research and the collision theory which states that reactant paticles collide with one another to cause the substances to react.
If I had another chance to carry out this investigation in a different way I would change a number of things. Firstly I would use different amounts and concentrations of both Hydrochloric acid and Sodium Thiosulphate. I would also change the colour of the cross on the boiling tube to observe what affect that has on the results of the investigation. I would also change the volume of the Hydrochloric acid that can be reacted with the Sodium Thiosulphate. I would change these things in order to compare the results between the two different investigations and also to observe what difference different concentrations make on both investigations.
If I had obtained any anomalous results I would have repeated those concentrations of Sodium Thiosulphate to find out why those results were anomalous.
If could have repeated the investigation the exact same way once or twice more to make sure my results are correct by comparing all the different results that I would have got.
I also could have used a wider range of concentrations of Sodium Thiosulphate in order to help me prove that my prediction was correct and also to check that the results were same to what I had already obtained.
