DrDAQ is a versatile instrument that connects to the USB port of any PC. Using the supplied PicoScope software it can be used as an oscilloscope, spectrum analyzer and signal generator.
The graph clearly shows that the temperature rises (bottom graph) and the oxygen level drops in a sealed bag of grass cuttings. As the oxygen level dropped, the rate of temperature rise slowed, so the bag was opened and the grass stirred to introduce more oxygen. The bag was then left open to the air. This caused a brief spike in temperature, which then dropped and thereafter continued to slowly rise.
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among systems of the Earth. Together with the nitrogen cycle and the water cycle, it is essential to ensure the Earth is capable of supporting life. It describes the movement of carbon as it is recycled and reused throughout the biosphere.
Because the DrDAQ measures oxygen content and temperature to 0.1% and °C, trends are seen quickly and this experiment may be used within a lesson to demonstrate that decomposing plants consume oxygen and give out energy in the form of heat. Ensure that all plant material is at room temperature before you start, or the temperature may drop initially. It is best to carry this experiment out in warmer weather, or the rate of decay may be very slow. Alternatively, it could be used as the basis of a range of projects investigating decay for Key Stages 3 to 5. It can be carried out simply with just the temperature sensor. It could be extended to investigate the best conditions for making compost, using temperature rise as a measure of microorganism activity.
This type of decomposition is quite sensitive to moisture levels of the plant material. If the grass cuttings are collected when too wet, the experiment may not work. Higher temperature rises can be obtained from a sack of fresh grass cuttings left open to the air (make sure they are not compacted).
This experiment was written by Susan Hammond of Woking College.