∙ Temperature – When the temperature is increased the particles all move quicker. If they are moving quicker, they are going to have more collisions. When you raise the temperature of a system the molecules bounce around a lot more (because they have more energy).
∙ Concentration – If the solution is made more concentrated it means there are more particles of reactant knocking between the water molecules, which makes collisions between the important particles more likely.
∙ Surface area – If one of the reactants is a solid then breaking it up into smaller pieces will increase its surface area. There will be more useful collisions.
∙ Pressure – Pressure affects the rate of reaction especially when you look at gases. When you increase the pressure the molecules have less space to move around. That greater concentration makes them collide with each other more often.
Safety
∙ Always wear goggles to protect your eyes from the acid
∙ Never heat the Hydrochloric acid because heating acid can be very dangerous
∙ Always wear gloves to protect your skin from the acid
Fair test
Concentration of the acid etc. affects the rate of reaction so to make sure it is a fair test I will keep all the factors the same. The only thing that won’t be staying the same is the temperature.
Ranges
I will use temperatures ranged between 10-100, going up in tens. So altogether I will have 10 different temperatures.
Replication
I will repeat the experiment at least 4 times and any results that are obvious anomalies will be repeated straight away. Obvious anomalies are results that are more than 3 seconds apart.
Apparatus
∙ Measuring cylinder (at least 25ml)
∙Conical flask
∙Pen and paper
∙Stop clock
∙Another measuring cylinder to measure 5ml of hydrochloric acid
Method
- First I measured 25ml of sodium thiosulphate with a measuring cylinder.
- Next I drew a cross onto a piece of paper and placed it under the conical
Flask.
- After that I heated the sodium thiosulphate to the different temperature
Ranges.
- Then I measured 5ml of hydrochloric acid with a measuring cylinder.
- At the same time I put both the sodium thiosulphate and the hydrochloric acid into the conical flask and started the stop clock
- When I could no longer see the cross On the paper I stopped the clock
- I carried this experiment out with the sodium thiosulphate at 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 degrees centigrade.
- I repeated the experiment at least 4 times at each different temperature.
Pre test
I did a pre test because they are very important. Pre tests are important so you can determine your ranges are ok. I tested the method out and have the pre test results at the top of the page.
Pre test results
Analysis
Increasing the concentration increased the rate of reaction. It was directly
Proportional. Also increasing temperature increased the rate of reaction. The results were a lot like my pre test results and my prediction.
Evaluation
Very accurate apparatus was used. There was very little chance of human
Error. My results are accurate because they are no more than 3 seconds apart
At each repetition. Accuracy was increased by doing repetitions and will
Reduce impact of anomalies.
Possible improvements
I could put a light sensor under the beaker that would overcome errors by human judgement. As soon as it reaches the desired point of cloudiness the underneath of the beaker will become dark. This will trigger it and log the time.
Future studies
My prediction of how concentration will affect rate of reaction is that as we increase concentration, the rate of reaction increases
