Method 1. Blend a small amount of either celery or liver with some water in a blender.
2. Place 20 cm3 of pH 9 buffer solution in a graduated cylinder.
3. Add a few drops of washing-up liquid. 4. Add a small amount of blended celery or liver. 5. Allow the reactants in the graduated cylinder to adjust to room temperature.
6. Add 5 cm3 of hydrogen peroxide to the graduated cylinder.
7. Observe the reaction that takes place for 15 seconds. The height of the foam generated gives a measurement for the amount of oxygen produced.
Fig. 6 Extended Investigation
Effect of temperature and pH on rate of reaction 1. Design an experiment using enzymes to investigate the effect of temperature on the rate of reaction.
2. Design an experiment using enzymes to investigate the effect of pH on the rate of reaction.
1. 2. 3.
The investigations in this chapter demonstrate the effects of changing different variables on the rate of reaction. These include: Particle size Concentration of solution Addition of a catalyst
4. 5.
Temperature pH
25.4 Energy and chemical reactions
The compounds on the left-hand side of a chemical equation are called the reactants. The compounds on the right-hand side are called the products. HCl + NaOH g NaCl + H2
O Reactants Products
In a chemical reaction there are always the same number of atoms in the reactants and in the products. The atoms are rearranged during the chemical reaction:
HCl + NaOH g NaCl + H2 O
Some arrangements of atoms require more energy to stay together than others. When the reactants require more energy to stay together than the products, the extra energy on forming the products is released as heat. These reactions are called exothermic.
Exothermic reactions give out energy as heat.
Height of foam
Enzyme (blended celery or liver), hydrogen peroxide and washing-up liquid
