Temperature:
Temperature is another factor that affects the rate of reaction. At low temperatures particles of the reactants has less energy, but when the temperature is high some of the heat energy is passed on to the particles therefore they have more energy and will move about and vibrate a lot faster. This makes the particles collide more often, so therefore the higher the temperature, the faster the rate of reaction.
Concentration:
Dilute acid has a lower chance of successful collisions acid it has a lower amount of acid particles. Highly concentrated acid has more acid particle, so there is more chance of successful collisions between the particles. When the particles collide often the reaction becomes faster therefore, if the concentration of an acid increase, the rate of reaction increases. This is also is backed up with the collision theory ‘If there are more particles per cubic centimetre, collisions will occur more frequently’.
Surface Area:
When a large object is cut into smaller pieces the surface area increases, as more of it is getting exposed to the air. This would be the same case for a reaction e.g. magnesium and hydrochloric acid. As more atoms are exposed the acid can react with more of the object so the reaction will become quicker.
Pressure/Light:
The increase in pressure forces the particles closer together. This causes collisions and an increased rate of reaction. If there was bright light photosynthesis, for example, would be very fast and the plant will give out more oxygen. In night there no light so photosynthesis will not occur and oxygen will not be produced.
Prediction
I think that the higher the concentration of sodium thiosulphate then the faster the reaction will take place. This is because of the collision theory. Higher concentration with a higher density of particles causes more particles of reactants to collide with sufficient activation energy. This means a higher rate of concentration.
As the hydrochloric acid is used up in this reaction, its concentration will drop and the rate of reaction will get lower.
Variables
The variables, which will affect the rate of reaction, are:
- Temperature
- Concentration of NA
Increasing the temperature will cause the particles to move faster. This means that the particles of reactants will travel a greater distance in a shorter distance causing more collisions. A large number of these collisions will meet or exceed activation energy so the rate of reaction will increase.
Apparatus
- Conical Flask
- Hydrochloric acid
- Sodium Thiosulphate
- Stopwatch
Diagram
Method
Set up the experiment as shown in the diagram. Wear safety goggles throughout the experiment to protect your eyes. I first of all added the correct amount of water that was needed and the right amount of hydrochloric acid to the conical flask and then got the stopwatch ready. With my finger on the “Start” button I pored the sodium thiosulphate into the flask and clicked the “Start” button as the reaction takes places as soon as the two chemicals start to react as soon as they touch. When the black cross wasn’t visible anymore, I clicked “Stop” on the stopwatch and recorded the time.
Results
Evaluation
I thought that the experiment went well. Everything went according to my plan. The procedure that I used I thought was appropriate and the correct equipment was used. I thought that I got these results because of what I explained in my prediction, collision theory.
Conclusion
I thought that my original prediction was correct. I thought that I got these results because of collision theory. There are more particles to collide with each other so the colour change was much quicker. The experiment was as fair as I could make it. I could have improved the experiment by using data logging equipment as this would have produced more accurate results and the test would have been fairer. If I was to improve my experiment I would use more precise equipment as the human eye is not very reliable.
Graph
Anthony Fayal Science Coursework 07/05/2007
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