Rates of reaction

Aim: To investigate the effect of surface area on the rates of reaction.

Hypothesis: I predict that when the surface area increases the reaction time will increase, this is because when we make pieces of a reactant smaller we will be increasing the number of particles which will react faster compared to a whole piece.

Independent Variable: Size of marble

Dependant Variable: Time (Rate of reaction)

Controlled Variables: Amount of water and amount of marble chips

Procedure:  

Materials: 

• 2 M HCl (hydrochloric acid)
• 3 different sizes of marble chips large, medium and powdered.
• Test Tubes
• Stop watch
• Spatula

               

       Figure 1#- Stopwatch                                Figure 2#- Calcium Carbonate

Figure 3#- Hydrochloric Acid

Method: 

Test 1.-

1. Take 2g of large sized marble chips.
2. Put 20ml of 2m HCl in a test tube.
3. Take the large sized marble chips and drop them into the test tube.
4. Start your stopwatch and stop it when the reaction stops when the large sized marble chip dissolves.
5. Record your observations.

 Test 2.-

1. Take 2g of medium sized marble chips.
2. Put 20ml of 2m HCl in a test tube.
3. Take the medium sized marble chips and drop them into the test tube.
4. Start your stopwatch and stop it when the reaction stops when the medium sized marble chip dissolves.
5. Record your observations.

 

Test 3.-

1. Take 2g of small sized marble chips.

2.   Put 20ml of 2m HCl in a test tube.

3.  Take the small sized marble chips and drop them into the test tube.
4.  Start your stopwatch and stop it when the reaction stops when the small sized marble chip dissolves.
5.  Record your observations.

Results:

Graphs: -

Conclusion-

Our hypothesis was proven to be correct as the results show that the powdered marble chips took the least time to react while the large marble chips took the longest time to react. The more finely divided the solid is, the faster the reaction happens. A powdered solid normally produces a faster reaction than if the same mass is present in a single lump. The powdered solid has a greater surface area than the single lump. Therefore the reaction occurs quickly compared to a whole lump. The diagram further explain-

Evaluation-

Evaluating this experiment, the experiment was not quite accurate because of numerous reasons-

• We added 2 grams of calcium carbonate which affected the rate of reaction, as we were meant to add only 0.5 grams. This was a major human error which changed our expected result.
• We also were not precise in our measuring as we were meant to pour 20 ml of hydrochloric acid and we due to human error poured 2ml more or less, this must have impacted our experiment.
• Another mishap was that we started our stopwatch before the calcium carbonate was dropped in the test tube as it was rather impossible to start the stopwatch at the exact time also we stopped the stopwatch 3-4 seconds after the reaction stopped.

Improvements-

We could have got a rather more accurate result if we would have been more careful.

Extension-

To extend this work we can-

• We can experiment about the rates of reactions in factors like- concentrations, catalyst and temperature.
• We can experiment with other more advanced factors that might slow the reaction rate.

Written by-

Kavya Sharma

8C (CLi)