Temperature
A higher temperature will give molecules more kinetic energy, therefore, they will move faster. The faster they move, the more collisions there will be. And the more collisions, the more chance of a reaction, which means that the higher the temperature, the higher the reaction rate.
Physical State
Reactions between liquids and gases are simple, as it is often easy for them to mix with one another. But with solids involved, the reaction is more complicated and there is a lower reaction rate. This is due to the fact that the reaction can only take place on the surface of the solid. Therefore, smaller sized particles are more likely to react than the large particles. This works in the same way as powder, a more divided powder has a higher reaction rate than a big lump.
Catalyst
A Catalyst has the ability to alter the rate of a chemical reaction without being used up or permanently changed. A Catalyst changes the energy in the reaction to provide an alternative route that lowers the Activation energy of each particle. This means that the energy will be more evenly dispersed, and more particles will have the energy required to collide successfully.
http://www.webchem.net/notes/how_far/kinetics/rate_factors.htm
Techniques to Measure Reaction Rate
You are able to measure the rate at which reactants are used up in a reaction or the rate at which products are formed in a reaction.
Table of Equipment
Variables
Same
The same card – otherwise there may be a slight variation in colour which could lead to a misjudgement of when the reaction is complete
Stopclock – There may be a slight difference in time if another one is used, this is best for consistency
Style of pipettes – Using different make pipettes may cause inaccurate measuring, as they may slightly differ
Temperature – Temperature affects reaction rate, it is important to make the experiment completely fair
Volumes of each Chemical – This will ensure that the test is even and fair on each concentration
The same chemicals –It is important to use the same Starch Solution etc. Otherwise, the second starch solution may slightly differ, slightly affecting the results
Different
Volume of KI – In order to make the different concentrations of the chemical that is being tested to see the change in reaction rate
Volume of Water- In order to make the different concentrations of the chemical that is being tested to see the change in reaction rate
Safety
Safety Goggles – Some chemicals are dangerous, and if an accident was to occur such as a splash, the Chemical may affect the eye.
Gloves – To avoid irritation of the skin, caused by the chemicals
Potassium Iodide Hazards
Potassium iodide may irritate the lungs or eyes.
Consumption of large amounts of iodide may harm the growing foetus, but normal use of this material in the laboratory will not expose you to dangerous levels.
This material is designated as "Not hazardous according to Directive 67/548/EC", a categorization which is applied to chemicals which are not regarded as likely to cause harm.
Potassium Peroxydisulphate Hazards
It's an oxidizing agent, which means it can be harmful if inhaled or if it comes into contact with eyes, nose, or other mucous membranes. Also, it has a relatively serious fire risk, where the gases could be poisonous if inhaled.
Sodium Thiosulphate Hazards
Sodium thiosulphate may be harmful if you swallow it. It may also irritate the eyes or lungs.
Starch Solution Hazards
May irritate the eyes or lungs, but this material presents a low hazard.
Method
The following method refers to the test conducted on the highest possible concentration of KI
- The mixture is made up of the following chemicals-
Potassium Oidide ( KI ) 5cm³
Sodium Thiosulphate ( Na2S2O3 ) 2cm³
Starch Solution 1cm³
Potassium Peroxydisulphate ( K2S2O8 ) 2cm³ - The Reactant
No Water ( H2O ) is needed as the highest concentration is being tested
- Measure out the measurements of each chemical given above precisely, using a new, clean Pipette each time. Squirt the chemical from the Pipette into a clean Boiling Tube. Do Not add the chemical Potassium Peroxydisulphate to the Boiling Tube, measure this chemical out in a separate clean Test Tube.
- When complete, there should be exactly 8cm³ of liquid in the Boiling Tube. Mix the liquid in the Boiling Tube.
- Ready your stopwatch, check the temperature and ensure it is maintained throughout all the tests.
- Place the White Card with a black cross on it directly under the Boiling Tube
- Add the Potassium Peroxydisulphate from the Test Tube to the Boiling Tube, and immediately start the stopwatch.
- Mix the liquid with 4 even stirs, use 4 even stirs for each concentration to ensure each test is completely fair.
- Observe the colour change of the liquid, look at the White Card through the liquid, from above. Immediately stop the stopwatch when the White Card is out of visibility due to the colour change of the liquid.
- Record the result in a table as shown below-
- Conduct the exact same test twice more, and record the results in the allocated space in the Results Table. Make sure that all environmental conditions (temperature etc.), hygiene conditions and stirs are kept the same.
- The proceed to make the 2nd concentration by adding 1cm³ of water to the Boiling Tube with the other chemicals.
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Repeat the experiment on the 2nd concentration and record all results on the Results Table
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Then create the 3rd concentration by adding 2cm³ of water to the Boiling Tube and so on, until you have tested 5 concentrations, up to 4cm³ of water. Each should have been tested 3 times, so in all, 15 tests have been conducted.