Rates of reactions

2P9: Monday 22nd November

Experiment

• Aim: To see what effect concentration has on the speed of a chemical reaction.

What is concentration?

High concentration Low concentration

Method• Collect: 2 bottles of Hydrochloric acid (different

concentrations), 2 small beakers, balance, Calcium Carbonate chips and filter paper

• Measure 25ml of Hydrochloric acid (low concentration) into one beaker

• Measure 25ml of Hydrochloric Acid (high concentration) into the other beaker

• Weigh out 2 separate quantities of Calcium Carbonate chips, each weighing 2g

• Add one sample of chips into each beaker of acid• Observe and record what happens in your

notebooks

Results:The calcium carbonate reacted faster with the concentrated Hydrochloric acid.

WHY???

Conclusion

• In the acid with the high concentration, there were more particles available to react which resulted in a faster reaction

• This result suggests that the higher the concentration, the faster the reaction

Experiment

• Aim: To see what effect the temperature has on the speed of a chemical reaction.

Method1. Measure 20ml of Sodium thiosulphate solution into a small

beaker using a measuring cylinder.

2. Mark a “X” on a piece of filter paper.

3. Place the beaker on the filter paper.

4. Measure 1ml of Hydrochloric acid and add it to the beaker – START THE STOPWATCH!

5. Stop the watch when the cross disappears.

6. Wash the solution down the sink and measure out another 20ml of Sodium thiosulphate.

7. Place the beaker in a hot water bath for about 2 minutes. Then repeat steps 2-5

Results

Reaction temperature (degrees Celsius)

Reaction time (seconds)

22oC

55oC

Conclusion

• The cross was obscured more quickly in the experiment performed at the higher temperature

• Therefore the experiment performed at the higher temperature gave the fastest reaction time

• This suggests that the higher the temperature, the faster the speed of the reaction

Explanation

• Increasing the temperature of a reaction gives the particles more energy which allows the particles to move around more quickly

• This in turn increases the number of collisions of particles, and therefore increases the speed of reaction

Speed of reactionsThe speed of a chemical reaction can be influenced by:

1.Particle size:

• Decreasing particle size (increasing surface area)

Increases the speed of reaction

2.Concentration:

1. Increasing concentration Increases the speed of

reaction

•Temperature:

• Increasing concentration Increases the speed of

reaction