Activation energy is the energy that an atomic system must acquire before a process can occur.
Key Factor:
The key factor we are investigating will be concentration, this is because it is the most accurate experiment we could complete, other than temperature. Surface area would be harder to get a set of accurate results for, therefore we would have to use more than the 3 marble chip sizes we have accessible (Small, medium, large). A catalyst would be unsuited to this experiment as catalysts are hard to obtain and are usually quite expensive. Temperature is hard to maintain at a constant temperature, and concentration is easy to get at different values by just diluting with water. Therefore concentration is the factor we will be investigating.
Prediction:
I think that the higher the concentrate the acid is the quicker the reaction will happen. This is because there will be more particles to react with, which would mean more collisions, thus speeding up the rate of reaction.
Method:
Use a burette to measure 40cm³ of water, pour into a conical flask. Then measure 10cm³ of Sodium Thiosulphate using a burette and add to the conical flask. Swirl the flask to mix the solution. Measure 5cm³ of dilute Hydrochloric Acid using a syringe. Place the conical flask onto a piece of paper marked with a cross. Add the 5cm³ of dilute Hydrochloric Acid. Swirl the flask and start the stopwatch. Look through the solution from the top and stop the stopwatch when the cross on the paper disappears. Repeat using the different concentrates of Hydrochloric Acid.
Fair Test:
To make our investigation a fair test we will measure the Sodium Thiosulphate, water and different acid concentrations accurately. We will do this by using a burette when measuring the Sodium Thiosulphate and water, by doing this we are making sure the measurements are completely accurate, by using a burette it is more accurate than a measuring cylinder because the measurements are in more detail. Temperature is also another way of making our experiment fair. Before adding the acid we measured the temperature of the solution with a thermometer to assure it was fair. We made sure we used exactly 40cm³ of water, 10cm³ of Sodium Thiosulphate and 5cm³ of different concentrates of Hyrochloric Acid. We will keep the amount of acid the same each time we repeat the experiment, we will do this by using a syringe that has measurements on the side. We will also use the same cross and the same person to measure when the cross disappears.
Safe Test:
To make it a safe test we will; wear goggles at all times, wash our hands after chemicals are handled, clear up spillages as soon as possible and clear the surface we will be working on before we start the experiment.
Results:
Conclusion:
My results fit with what I said in my prediction because I predicted that the higher the concentrate of the acid the quicker the reaction would be, and this is proved in the results. When the concentration is at its lowest it took 463 seconds on average and at the highest concentration it only took 172 seconds on average. This is because the higher the concentrate the more particles there are to react with, hence a fast rate of reaction.
Evaluation:
I could improve my experiment by measuring the temperature of each solution before the experiment, this would make it a much fairer test. We could also use light meters so when it gets to a certain amount of light we stop the timer, this would increase the accuracy of the experiment. Most of the results fitted well as we didn’t have any anomalous results. I am pleased with how the experiment went.
