How I will keep this a fair test
To keep this a fair test I am going to make sure that for each experiment all the following variables stay the same.
. Same wattage of bulb is used.
. Same concentration of sodium thiosulphate.
. Same volume of reactants.
. Keep the position of the lamp the same.
. Make sure the room temperature is about the same on each day.
The only variable I will change in the main test is the concentration of sodium thiosulphate. The reason for keeping the other variables the same is so that all the results match up because if, for example, the room temperature was a noticeable amount hotter one day then it was another the results would change because based on the ‘collision theory’ warmer particles move around much faster then colder ones therefore they are much more likely to collide and react so something like this would completely mess up the whole experiment.
Prediction
I think that when the concentration of sodium thiosulphate is higher the reaction will take place much faster. My idea is mainly based on the ‘collision theory’, which is explained elsewhere in this piece.
Hydrochloric + sodium Sodium + sulphur + sulphur
Acid thiosulpahte chloride dioxide
Also I think that when a higher concentration of hydrochloric acid is used it will make the reaction happen much faster because there are more particles moving around in the mixture and therefore they stand a much greater chance of colliding and creating a successful reaction.
Method
Setting up equipment
. Plug in lamp.
. Make sure USB data logger is connected and turn computer on.
. Set up clamp with logging sensor facing upwards touching the bottom of the clamped vial.
. Make sure the logger is turned on, if not press the green button once.
Before you start
. Load up data logging insight and select datameter 1000 from the top drop down box and USB from the bottom dropdown.
. Once the program is loaded go to set-up, time span and make sure it is set to at least 4 minutes for the weaker concentrations.
. Also check along the left side that the logger is measuring light by going to set up then selecting sensing.
Doing the experiment
. For each experiment you must measure 25ml of sodium thiosulpahte, the concentration of this will vary depending on the one you want to use.
. Also for each experiment you will need 2.5ml of hydrochloric acid, which in our main experiment was always the 2Molar concentration.
. Pour the 25mls of sodium thiosulphate into the glass vial.
. Squirt the hydrochloric acid in the vial with the sodium thiosulphate with a syringe and instantly turn on the lamp and press ‘start’ on the data-logging program so the computer can begin to record the data. Note: it is best that two people do this part
. Stop it when the light intensity goes just below 76%.
. Go to analyze then data from the menu bar and find the time where it reached 76% light intensity and record the time.
. Do this 3 times for each different concentration used convert the minutes to seconds then work out the average.
Particle Diagrams
This particle diagram (above) shows a high concentration reaction
Preliminary testing: Table of results
Main test: Table of results
Time Graph showing the time taken to reach 76% light intensity.
Rate of reaction graph
Rates of reaction coursework
Analyzing section.
When the concentration of sodium thiosulphate was higher the reaction was faster this happened because, based on the collision theory when there are more particles in one are (the higher concentration) moving around they stand a higher chance of colliding and making a successful reaction. When the concentration of sodium thiosulpahte was lower there was more gaps between the important particles and the water particles so there was a much greater chance of them not colliding and not making a successful reaction. All this information is clearly shown in the particle diagrams and the two scatter graphs.
My table of results from the main test shows that when a lower concentration of sodium thiosulphate is added such as the 0.05M concentration the time taken to reach 76% light intensity is much less (in this case the reaction took 148 seconds). That is a large difference compared to the 0.15M concentration which only took an average of 30 seconds to reach 76% light intensity. Also there is an even larger difference between the 0.05 concentration and the 0.25 concentration which only took an average of 18 seconds to react enough to change the light intensity of the mixture to only 76% light intensity.
The results I got in my main test reflected my expectations because even though my prediction was quite basic it followed the basic idea that when the concentrations of each substance are greater there is an increased chance of them colliding. This is because there are more of the important particles moving around in the solution and less water particles therefore the chance of the important particles (hydrochloric acid and sodium thiosulphate) colliding is much greater and thus speeding up the reaction.
Rates of reaction coursework
Evaluation section.
For my main test I found that all my results were very reliable as both of my lines of best fit on each graph followed a steady pattern. This shows that there weren’t too many errors made in the main testing and if there were any they were very minor.
Although our results were good we found that there was one anomalous result on the 0.15M concentration of sodium thiosulphate test. I think that was because we did that after 6 other tests and the black paper covering the vial was beginning to get very wet and began to split apart so therefore more light got in and caused the reaction to happen a few seconds faster which was enough to make it show up on the graph.
An improvement would be to use a new vial and piece of black paper for each experiment this would stop any unwanted light getting through gaps in the splitting wet paper and affecting the reliability of the experiment. Also it would make sure there was no water left in the vial that would slightly change the concentration of the substances.
There are many other reasons why there could have been errors in the experiment for example, if the was more light in the room one day compared to the next it would make the light intensity slightly greater then it would have been on the day with less light. The only solution for a problem like this would be to perform the experiment in a room where the light could be measured and easily set to a required amount to make sure it was a completely fair test and all the results were 100% reliable. Another problem might be the room temperature because as we know from the ‘collision theory’ when the temperature is increased the particles will move much faster which means there will be more collisions. The best way to solve this problem would be to perform the test in a temperature controlled room so you could make sure that the whole test was done at the same temperature.
New rates of reaction coursework: using hydrochloric acid and marble chips (calcium carbonate).
Equation for the new experiment:
+ + +
The aim of this experiment is to investigate if different concentrations of hydrochloric acid affect the rate of reaction between the acid and the marble chips. The variable to be measured would be the amount of Carbon dioxide (CO2), which was given off by the reaction.
Prediction
The higher the concentration of the acid the quicker the reaction will occur and more gas (carbon dioxide) will be produced. As you increase the concentration of the acid, there are more acid particles in the same volume. Therefore there is a greater chance of the acid particles colliding, and reacting, with the particles on the surface of the marble.
Method
- Put a set amount marble chips into the test tube
- Pour a set amount of hydrochloric acid onto the marble chips.
- Start a stopwatch.
- Take readings every thirty seconds for four minutes to see how much carbon dioxide the marble chips and hydrochloric acid have produced.
- Do each experiment 3 times and take an average reading.
