Investigating the factors which effect the rate of a chemical reaction.

• Temperature
• Surface Area
• Concentration
• Catalyst

Temperature:-

  In a cold reaction mixture the particles are moving quite slowly- the particles will collide with each other less often, with less energy, and fewer collisions will be successful.

 

        

If we heat the reaction mixture the particles will move more quickly- the particles will collide with each other more often, with greater energy, and many more collisions will be successful. So this would make the rate of reaction/ speed increase.

More likely successfully collisions if the temperature is increased!

Surface Area:-

Large particles like lumps of marble chips have a small surface area in relation to their volume – fewer particles are exposed and available for collisions. This means less collisions and a slower reaction.

                         

Small particles like powdered marble have a large surface area in relation to their volume – more particles are exposed and available for collisions. This means more collisions and a faster reaction.

                       

The larger the surface area the quicker the reaction!

Concentration:-

   In a reaction where one or both reactants are in low concentrations the particles are spread out and will collide with each other less often resulting in fewer successful collisions.

In a reaction where one or both reactants are in high concentrations the particles are crowded, close together and will collide with each other more often, resulting in an increased number of successful collisions.

There will be more particles to collide and a faster reaction rate.

In the experiment Sodium Thiosulphate particles collide with Hydrochloric Acid with enough energy for a reaction to take place.

The higher the concentration of Hydrochloric Acid the more particles there are for collisions, and the faster will be the rate of reaction.  

Catalyst:-

A catalyst is a substance which increases the rate of a chemical reaction, without being changed during the process.

                               

Hypothesis;-

The higher the concentration of Sodium thiosulphate the faster the reaction with hydrochloric acid.

Supporting Information;-

I think that the higher the concentration the faster the reaction because when two successful collisions collide they become faster as the concentration increases.

In this experimentation I will keep the concentration of Hydrochloric acid the same and alter the concentration of Sodium thiosulphate. If the concentration is doubled, the speed doubles. This is because the irons are closer together in a concentrated solution. The more often they collide, the more chance they have of reacting.

Preliminary Work;-

You do not want the speed of the reaction to be too slow or too fast otherwise the results may be inaccurate!

I need to repeat my experiment to be accurate!

Increasing the amount of Thiosulphate will give the solution a much greater depth…

Plan;-

During this experiment I will need;

• White Tile with black cross- As my guideline, so I can see the black cross as the beaker is on it.
• Beaker- To mix all of the chemicals around.
• Sodium Thiosulphate- Chemical I will be using.
• Hydrochloric acid- Chemical I will be using.
• Water- I will be using in the solution.
• Stop clock- To start and stop the clock when the reaction starts and finishes.
• Pippet- To add the chemicals in to the test tubes.
• Test tubes- To put the chemicals in, before into the beaker.

I plan to collect my evidence which will be valid in a table and then into a graph. I believe my test to be fair as I will start and stop the clock at the right time and can prove my results to be correct by doing the same experiment more than three times!

I am going to make as many measurements as I can in the time I have…

I will ensure the procedure is safe by;

• Wearing goggles
• Tying back my hair
• Standing up and not sitting down
• Not adding the wrong chemicals
• Asking for help if needed

When the marked cross could not be seen the time was stopped and recorded. This was tested four more times and other concentrations tested five times.

Fair Test;-

I will make this experiment a fair test by doing the reaction all on the same day so that the room temperature does not increase or decrease.

Materials;

• White tile with black cross
• Beaker
• Sodium Thiosulphate
• Hydrochloric acid
• Water
• Stop clock
• Pippet
• Three test tubes

Method;-

1. Tie your hair back, put goggles on and tuck in your chair under the table.
2. Gather all the materials provided.
3. The tile was marked with a cross and put onto the table where 10cm3 of Hydrochloric acid and 10cm3 of Sodium thiosulphate were measured out, (as shown in results table).
4. Immediately start the stop clock when all of the chemicals are placed in the beaker.
5. When the marked tile is not to be seen and the solution has turned opaque, stop the stop clock and record your first set of results.
6. Repeat this procedure, measuring the right amount of, water, hydrochloric acid and sodium thiosulphate, (referred to the results table).  
7. After you have recorded your results on the chart then repeat them at least two more times for your results to be accurate and improve reliability of the results.
8. When finished tidy away carefully, trying not to spill any chemicals on the floor or on you.

Results;-

To make sure that my results were as precise as possible I made sure that during the experiment I had started and stopped the stop clock at exactly the right time. Making sure I had the right amount of measurements for the hydrochloric acid, water and sodium thiosulphate I have faith in my results as I have done the experiment more than three times giving my average results as close as I could.

 

Average Results

The graph shows me that the

Concentration of Sodium Thiosulphate is Inversely Proportional to the rate of reaction.

If the acid concentration is doubled, the speed doubles. This is because the irons are closer together in a concentrated solution. The closer together they are, the more often the irons collide. The more often they collide, the more chance they have of reacting.

Analysis and Conclusion;-

The graph shows me that the rate of reaction is proportional to the concentration of Sodium Thiosulphate, 1/time x concentration.

Speed of reaction x concentration.