I predict that when the temperature increases then the rate of reaction will also increase. I think this because, when the temperature increases, the particles of the liquid would move faster and cause more collisions. So, when the temperature increases, there is more kinetic energy, so there are more collisions and these collisions succeed to react as they have more energy than the activation energy. When the temperature decreases, there will be less kinetic energy so there are less collisions and these collisions fail to react as they have less energy than the activation energy.
For my experiment I chose the mixture 10 ml Acid, 10 ml Sodium Thiosulphate and 15 ml water. I chose this mixture because, when I would heat this then the time it gave wouldn’t be too slow or too fast. It gave a fair length of time so a good graph can be made from it.
The activation energy can be shown in this simple diagram.
This diagram clearly shows that when the particles have no or less than the activation energy then, there is no reaction but when they have more energy than the activation energy, then there are reactions.
Preliminary Work:
I am going to obtain a number of results to find out which is the best concentration of Sodium Thiosulphate, Hydrochloric Acid and Water.
I decided to use a concentration of 10ml of Sodium Thiosulphate, 15ml of water, and 10ml of Acid. I chose this because this has a decent time of reaction at room temperature and when it is heated up it will still be measurable. I think that this wont get too fast or too slow and it will give a good set of results.
Obtaining Evidence
Results:
Back Up Results:
These were taken off a computer. When the light shines through the conical flask, which has Sodium Thiosulphate and Hydrochloric Acid inside it. The light that passes through the substance is picked up by the light sensor. We stopped the experiment when the sensor picked up 70% of the light.
You can see this on this diagram. You can see the light sensor underneath the conical flask and the lamp above the flask. The light sensor picks up the light coming through the reacting substance. This acts just the same as my original experiment.
Backup Results:
To work out rate, we took 1000 and divided it by the time leaving me with the rate.
Method:
For my experiment I am going to
- Collect my apparatus, (listed below) and arrange it as shown below.
- I will collect 10ml of Sodium Thiosulphate and Hydrochloric Acid and 15ml of Water so it totals to 35cm3.
- I will then pour the Hydrochloric Acid into a 100cm3 conical flask. After this I will put the conical flask onto a gauze and tripod and heat it with a Bunsen burner until I get it as close to the desired temperature as possible.
- I then take the temperature (either 20,40,60,80,100*c) on a 0-100*c thermometer and put the conical flask on top of a black cross on white paper. I will do this quickly so as little heat as possible is lost.
- I will next add the Sodium Thiosulphate and water.
- I am going immediately time this with a stop clock.
- I will keep looking over the top of the conical flask so this experiment is fair and as soon as the cross has disappeared I will stop the clock.
- I am going to make a note of these times.
- After the experiment has finished completely then I will rinse my apparatus thoroughly to remove any excess particles and keep the experiment as fair as possible. I will repeat this experiment 5 or more times so any anonymous results will show up.
- I will do this at 20,40,60,80,100*c each these temperatures wont be exact as human error will prevent 100% accuracy.
- Then, I’ll plot a graph showing the speed of reaction with mixture.
Apparatus:
- A burette, - to measure the liquids accurately
- 3 X 25ml - beakers for all of the different mixtures
- A stop clock - to time this experiment accurately for finally plotting on a graph.
- A conical flask - to finally mix all the mixtures together.
- A heatproof mat
- A Bunsen burner - to heat a chosen mixture.
- Gauze - to rest the chosen substance on whilst heating.
Analysing Evidence:
I have found out that when the temperature is increased then the rate of reaction also increased. Also when there is more water added then the time it takes to react is much slower. My original prediction was that when the temperature increased then the rate of reaction would decrease. I know this because, when the temperature decreased the time it takes for the reaction to take place increased and when the temperature increased the time it takes to react decreased.
e.g.
Temperature (*c) Time(s) Rate (S-1)
10*c 134 7.46
100*c 12 83.33
My results also prove my scientific explanation as when the temperature increased, the time decreased and the rate increased. This shows that when the temperature increased the time it took for the reaction to take place also decreased. This shows that more reactions took place in a shorter time so my theory of ‘temperature increase time decrease’ was correct.
Evaluating Evidence
On my graphs on the backup results there seems to be an anonymous result on both graphs. I took repeat readings in-case I didn’t rinse my apparatus as well, and remaining particles were still in the flask I was using, which would have affected my results. I think my experiment went quite well overall. My range of values were very satisfying as I took a number of readings which show the rule of when the temperature is increased then the rate of reaction is also increased. If I did this experiment again I would change the amount of time I took for getting my temperatures more accurate.
