- Surface area
-
Temperature (in my experiment the temperature will be at room temperature).
- Catalysts
- Concentration; this is the volume of a particular thin in another e.g. 1 tea spoon of sugar in 200ml of tea or 2 tea spoons of sugar in 400ml of tea these two have the same concentration of sugar. For a higher concentration of sugar you could have 2 teaspoons of sugar in 200ml of tea etc…
- Surface area; increasing the surface area will increase the rate of reaction e.g. if you have a ball of cotton in a petri dish an you put a strong acid to dissolve it would take a longer time to dissolve if you had the same volume of cotton but spread out in a petri dish this is because the acid must penetrate through the ball of cotton which takes a longer time.
- Temperature; if we increase the temperature of something it increases the rate of reaction because at particle level heat is the kinetic energy of the particles e.g.
- Catalysts; increase the rate of reaction without being used up them selves i.e. stirring or shaking.
All these above factors also contribute to collision theory
Collision theory-this is an idea that helps us to understand reactions. Collision theory says that for a reaction to be possible particles must:
- Be able to collide with each other
- Do so with enough energy to cause a reaction
We can then use collision theory to understand how the above factors affect the rate of reaction.
- Temperature: when the temperature of something increases the particles of the thing are given more kinetic energy so the collide faster with more power.
- Concentration; a higher concentration has more particles in a given volume so they find each other faster so the rate of reaction is increased because more particles collide faster e.g.
- Surface area: a larger surface area means more particles are exposed to be able to collide and react so this also increases the rate of reaction e.g.
- Catalysts: provide an alternative or more than one way to produce energy for collisions to happen so a reaction can happen faster.
In my experiment I am going to investigate how concentration affects the rate of reaction so I can obtain more results, if I am not investigating temperature because it needs a better lab to control.
Prediction: I predict that the higher concentration of sodium thiosulphate in a constant/controlled volume of hydrochloric acid will enable the rate of reaction to increase because I know that in a higher concentration there is more particles in the volume so it is easier for the particles to collide which will increase the rate of reaction.
Fair test: To insure that the experiment I carry out is fair each time I shall:
- Use the same equipment exactly each time and in the same way
- Use the same volume of sodium thiosulphate and hydrochloric acid for each test
- Try and achieve the same temperature in each test because I know that temperature is one of the factors that affect the rate of reaction. As I am only investigating how concentration can affect the rate of reaction I do not want the temperature to contribute to my results.
Method: I am going to gather the following list of equipment needed:
Stop Clock
Safety Goggles
Apron
Conical Flask
Measuring Cylinder
Square of paper with a cross in the middle
Thermometer
Sodium Thiosulphate (0.8 mol, 0.6 mol, 0.4 mol, 0.2 mol)
Hydrochloric acid (1 mol)
Then I will:
- Wear all the safety equipment
- Measure 50ml of sodium thiosulphate (various concentrations each time) in a measuring cylinder and 5ml of hydrochloric acid in a separate measuring cylinder
- Place the conical flask on top of the square of paper
- Mix the sodium thiosulphate and hydrochloric acid in the conical flask and with the stop clock time how long it take for the cross on the square of paper to no longer be visible
I will repeat the above experiment for the four different concentrations recording the time it takes for the cross to disappear and the concentration level of the chemicals used.
Observation: I have now completed the experiment on rates of reaction to the criteria above to produce the below results.
Analysis: From the above results we can see the rate of reaction depended on the concentration of sodium thiosulphate. This experiment shows that as the concentration of sodium thiosulphate increased the time the reaction took was decreased or vice verse as the concentration decreased the rate of reaction increased. This means according to my results as the concentration of sodium thiosulphate increases in hydrochloric acid so does the rate or speed of the reaction. I can explain or understand how this happened through collision theory because in a higher concentration in a particular volume there is more particles of a particular thing so they collide easier and quicker as there is more of them and they are closer to each other this is what causes the reaction to happen faster when the concentration is increased as the collisions are more powerful and faster.
I can prove this with my results.
Evaluation: My results for the above experiment investigating rates of reaction and concentration are quite reliable as the experiment was done in the standard controlled conditions however even though the experiment only investigates the results for the above experiment it also gives a general idea of how increasing concentration increases the rate of reaction through collision theory and the factors of a reaction for any similar experiment.
I think I could improve the experiment by bringing other factors of reaction into it and investigating them as a whole how they affect the rate of reaction but for such an experiment more controlled conditions for temperature must be made to make it a fair test.