S2 Chemistry Rates of Reactions

1.1 Reaction Rates Learning Intentions We are learning about changing the rate of chemical reactions

Success Criteria I can list the 4 methods a reaction can be made faster. I can describe the effect of a catalyst and an enzyme on a reaction I can do experiments to show how a reaction’s speed can be increased. I can evaluate and explain graphs showing speeds of reactions. I can explain everyday reactions and how to speed them up.

Particle Size Apparatus 0.5M hydrochloric acid chalk lumps chalk powder 2 boiling tubes test tube rack

Particle Size Method Two boiling tubes were ¼ filled with 0.5M hydrochloric acid. 4 lumps of chalk were put into one boiling tube A similar quantity of chalk powder was put into the other boiling tube Record your results

Particle Size Results Decreasing the particle size (making the bits smaller) increases the rate of reaction.

Temperature Apparatus glucose powder Benedict’s solution Metal beaker Bunsen and bench mat Tripod and gauze

Temperature Method Half fill the metal beaker with water. Heat it with a blue flame until it is boiling then switch off the bunsen. ¼ fill two test tubes with water. Put a spatula of glucose into each test tube. Put 10 drops of Benedicts into each test tube Place one of the test tubes into the hot water Record your results.

Temperature Results Increasing the temperature increased the rate of the reaction.

Concentration Apparatus 0.5M sodium thiosulphate 0.5M hydrochloric acid 100ml beaker 10ml measuring cylinder

Concentration Method Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker

Concentration Method Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker Again using a measuring cylinder, measure out the required volume of acid and water and place in a second beaker

Concentration Method Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker Again using a measuring cylinder, measure out the required volume of acid and water and place in a second beaker Pour one beaker into another and start the timer

Concentration Method Measure 20ml sodium thiosulphate using a measuring cylinder and pour into a 100ml beaker Again using a measuring cylinder, measure out the required volume of acid and water and place in a second beaker Pour one beaker into another and start the timer Stop the timer when the cross underneath the beaker can no longer be seen

Table of Results 1 20 40 0.5 2 16 4 0.4 3 12 8 0.3 0.2 Volume of (cm3) Sodium thiosulphate (cm3) Hydrochloric Acid Water Total Volume Conc HCl (mol/l) Time 1 20 40 0.5 2 16 4 0.4 3 12 8 0.3 0.2

Concentration 2 Apparatus 1M hydrochloric acid 4M hydrochloric acid 2 boiling tubes 2 pieces of zinc

Concentration 2 Method ¼ fill one of the boiling tubes with 1M acid Place a piece of zinc in each of the boiling tubes and observe the reaction

Concentration 2 Results Increasing the concentration increases the rate of reaction

Summary To speed up a chemical reaction you could - Increase temperature Increase concentration Decrease particle size

Catalysts A catalyst is a substance which increases the speed of a chemical reaction without itself being changed.

Effect of catalyst ¼ fill a boiling tube with 1M hydrochloric acid

Effect of catalyst ¼ fill a boiling tube with 1M hydrochloric acid Place two pieces of zinc into the boiling tube and observe what happens.

Effect of catalyst ¼ fill a boiling tube with 1M hydrochloric acid Place two pieces of zinc into the boiling tube and observe what happens. After a few minutes, add a ¼ spatula of powdered copper

Effect of catalyst When copper was added to the test tube the reaction rate was clearly faster. The copper did not take part in the reaction as it could be collected at the end. The copper acted as a catalyst.