Fair Test
The factors that I will keep the same are:
Temperature because changing this can speed up or slow down the reaction. If the temperature was made higher this would make the particles speed up.
Thiosulphate concentration because changing its concentration will give the acid more or less particles to react with.
Light intensity because the light differences can make the particles get warmer and speed up or colder and slow down.
Apparatus
- Conical Flask
- Goggles
- Pipette
- Stop Clock
- Sodium Thiosulphate Solution
- Acid
- 10cm Measuring Cylinder
- 100cm Measuring Cylinder
- 250cm Glass Beaker
- 250cm Plastic Beaker
- Water
Plan
First I will put my goggles on as I am working with corrosive chemicals.
Then I will draw a cross on a piece of paper (it will be red). I will them place a conical flask on the paper. Then I will add my thiosulphate. There will be 50cm of it. Then I will ad the hydrochloric acid which is of varying amount. I’ll swirl the mixture then start the clock. I’ll look down into the conical flask till the cross disappears. When it does I will stop the clock. I will repeat it 3 times for each amount of acid. I’ll put the results in a table and work out the
averages.
Safety
To keep myself safe I will make sure that none of the chemicals come into contact with my skin. I will make sure that I don’t breath in too Much of the fumes from thiosulphate as they are corrosive and can be can be dangerous to people with asthma.
Analysing the results
As I diluted the acid the reaction time gets slower.
I know this because when I had 50cm of acid and 10cm of water it took 21.93 seconds for the cross to disappear and when I had 20cm of acid and 40cm of water it took 37.07 to disappear. Which is slower than the first time.
As I decrease the acid concentration there is less and less acid particles there is less and less acid particles for collisions with the thiosulphate particles. This means it takes longer for all the particles to collies. react and make the red cross disappear.
Prediction: Was I right
My prediction was that as I make the acid concentration lass and less the reaction will be slower. I was right as my graph shows.
Evaluation
My method was good enough to give a firm conclusion be we used the same apparatus and there was no results were out of pattern.
My results don’t need to be retested because the follow the same pattern all the way through.
The experiment could be done again because we had to tell when the cross was gone with out eyes. We could do it again with a device which could detect when it has disappeared.
To make the results even more accurate we could have taken more for each section or we could have changes measurements in a different scale.
We could have taken 5 readings for each one rather than 3 and we could have changed measurements in 5cm and not 10cm .
I think that we would get the same pattern of results if I repeated the experiment. Maybe not the exact results but the pattern would remain the same. I think I took enough results to be certain but in a perfect world I would like to repeat the experiment at least one more time.
To be a really fair test I would have liked to have used acid and thiosulphate from the same batch but others were using it too so this wasn’t possible.
To provide extra results I could do more of the experiment and other people could do it also.
