Energy because they are all bunched together and there is no room for the particles to gain energy, move and collide, this slows down the rate of reaction.
Large Surface area
It is a lot easier for the particles in this diagram to gain energy, move and cause more collisions because they are all spaced out (Large surface area). The particles will gain the activation energy needed to cause the product to be formed quicker, and so the rate of reaction will increase.
- If the Concentration of the reactants increases
If the concentration of the reactants decreases the rate of reaction also decreases because if there is a weak concentration of the reactant then it will take longer for the reaction to occur because the particles will not collide, due to lack of energy, but if there is a higher concentration then the particles will react quicker, because then the activation level is reached more quickly and so the overall reaction rate is increased.
Prediction
I predict that when the temperature of Sodium thiosulphate is increased the reacting particles gain energy and move faster. As the particles move faster there are more collisions, since the collisions are more energetic, the rate of reaction will be increase affected causing sulphur to be formed quickly.
Sodium thiosulphate + Hydrochloric acid = Sulphur
Factors, which will affect the investigation:
- The size of the X
- Concentration of Both Reactants
- Volumes of both reactants
If I am going to make this experiment a fair test, I must keep the size of the X the same, the amount of acid and the concentration of the acid the same as well as the amount and concentration of sodium thiosulphate. I will change the temperature of the sodium thiosulphate to prove that temperature affects the rate of reaction, and to make the results more reliable I will use a range of 5 Temperatures. For accuracy, I must repeat the experiment at least 3 times and obtain the average.
Apparatus:
- Sodium thiosulphate
- X on a piece of paper
- Clamp stand
- Burette
- Pipette
- Bunsen Burner
- Safety mat
- Safety Glasses
- Conical flask
- Measuring cylinder
- Digital Stop clock
- Thermometer
Diagram:
Plan:
- Collect all apparatus and set it up as shown in the diagram
- Using a marker, mark and X on a piece of paper
- Carefully pour Hydrochloric acid (Hcl) into a Burette using a filter funnel and bring it up to 25cm3
- Measure out 25 cm3 of Sodium thiosulphate using a pipette.
- Put the sodium thiosulphate into a conical flask and place it in beaker of water, which is on a tripod over Bunsen burner. (Known as a water bath)
- Take the sodium thiosulphate off the heat when it has reached the temperature needed.
- Place the Conical Flask on the X with the sodium thiosulphate in it.
- Add 2 cm3 of Hydrochloric acid from the burette to the Sodium thiosulphate.
- Start the stop clock and when the X on the paper disappears stop the clock and record the time in seconds.
Safety
- Take care with measuring the Hcl acid and sodium thiosulphate.
- Be careful with the water bath
- Light the Bunsen burner only when the air inlet hole is half open half closed.
Preliminary Experiment Results
Preliminary Experiment
Initially I had planned to use a range of different temperatures from 20 C, 30 C, 40 C and 50 C, but I discovered that I couldn’t get the exact temperature. I was able to time the X disappearing when I used the temperatures at 20 C AND 30 C but as I increased the temperature to 40 C and 50 C, I found it more difficult to time the X disappearing and to get the correct temperatures. To solve this problem I decided to decrease the concentration of HCL acid from 1 molar to 0.5. molar and reduce the volume of acid from 2 cm3 to 1cm3. I have also decided to start the stop clock as soon as I started to add the HCL acid to the sodium thiosulphate.
Actual plan
The plan is the same as the preliminary plan. However I will pour a 05. molar Hcl acid into the burette. I will add 1cm3 of Hcl acid to the conical flask. I will start the stop clock as soon as I add the Hcl acid to the sodium thiosulphate.
Actual Results
What does graph 1 and 2 show me?
Graph 1 shows me that as the temperature increases the time decreases. This also shows me that when you increase the temperature Sulphur will be formed at a quicker pace.
Graph 2 shows me that as the average time for the x to disappear is increased so does the rate of reaction.
In graph two one of my results falls greatly away from the line of best fit. This is due to Human error. This may be because when I was trying to reach the temperature of 30 C, by heating the Sodium thiosulphate over the Bunsen burner, when I took it off the sodium thiosulphate cooled down slightly causing me to get a slightly lower temperature then 30 C.
I tried to overcome Human error by repeating the experiment and obtaining the average. I also used a burette and pipette for accuracy, instead of a measuring cylinder.
My results do agree with my prediction, which was when the temperature of Sodium thiosulphate was increased Sulphur would be formed quicker. The particles were not colliding faster at 25 C compared to 50 C. This tells me that as the temperature increases the time taken for the x to disappear decreases. This is because the reacting particles gain energy (activation energy) and move faster. As the particles move faster there are more collisions (collision theory), since the collisions are more energetic, the rate of reaction will be affected causing the rate of reaction to increase.
I could further improve the Experiment if I was too use the proper and more accurate equipment e.g. A light gate, because it sees either Black or white, this would help when being able to know if the X had disappeared.