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Decomposition
CAUTION: INVOLVES HYDROGEN PEROXIDE solution - Can irritate skin/eyes. Wash any spillage with large amounts of water.
You will need:
- safety spectacles/goggles
- 4 x small beakers
- 1 small potato
- spoon/spatula
- sharp knife
- plastic trays
- dried yeast
- washing up liquid
- mortar and pestle if available
Hydrogen peroxide (H2O2) decomposes to produce water and oxygen gas:
What we did..
We prepared four beakers and put an equal volume of hydrogen peroxide solution in each beaker. We added a "good squirt" of washing up liquid to each beaker and mixed it. We prepared four different mixtures ( catalysts) - one for each of the beakers. We then added these mixtures to the contents and observed the results.
- potato cubes
- potato paste (mashed up with pestle and mortar)
- dried yeast made into a paste with water
- potassium iodide ( made into a solution in water)
What we found out..
All four of the catalysts caused the hydrogen peroxide to foam up . The potassium iodide solution produced a brown colour as well. We decided which of the four catalysts worked best and caused the fastest reaction.
We put them in order. Our results are in the table:
| MM | JR | OC | total | |
| potato cubes | 4 | 4 | 4 | 12 |
| potato paste | 2 | 2 | 1 | 5 |
| potassium iodide solution | 3 | 3 | 3 | 9 |
| yeast paste | 1 | 1 | 2 | 4 |
The tekkie bit..
Hydrogen peroxide has the chemical formula H2O2
Hydrogen peroxide is unstable and will therefore decompose to produce oxygen gas and water:
This decomposition reaction is slow are ordinary temperatures but is speeded up by certain other substances which do not themselves get used up. Substances which do this are called catalysts.
Some catalysts are found in plant and animal cells and are therefore "biological" catalysts. Biological catalysts are known as Enzymes and are very important in life processes. In our experiments the enzyme we used is known as catalase and can be found in potato and in yeast ( as well as animal organs such as the liver).
Making potato into a pulp increased the reaction speed because the pulping process breaks the potato cell walls and releases the enzymes inside them.