• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

We will set up an experiment using 8g of bread, and 0 - 40ml of water in each Petri dish. I will then investigate how varying the amount of moisture affects the rate of decay. The bacteria respire on the food.

Extracts from this document...

Introduction

AT1 - Decay Plan We will set up an experiment using 8g of bread, and 0 - 40ml of water in each Petri dish. I will then investigate how varying the amount of moisture affects the rate of decay. The bacteria respire on the food. The equation is for respiration is: Food + Oxygen Carbon Dioxide + Water. Other things I could vary are the amount of Oxygen and the Temperature, however I could only take 3 readings from the temperature - the fridge, room temperature, and the incubator. To measure the results, each piece of bread will be weighed. To keep it a fair test, the amount of oxygen, the shape and density of the bread will all have to be kept the same. I predict the decay increases as the amount of water is increased, because there is more water for the bacteria to live on. Obtaining Experiment 1 Weight Before Decay/g (Including weight of water and Perti dishes) ...read more.

Middle

of water, such as 40ml, the decay went down again because there was too much water to too little oxygen, so the bacteria could not reproduce as fast, as the conditions were too anaerobic when the bread was waterlogged. If there is no oxygen, the organisms causing the decay cannot grow. However we didn't have the equipment in the lab to test this. The end results however were correct, but I think the main reason that they had lost so much mass was evaporation. The Petri dish was designed so that water vapour could escape, gasses could exchange, but no bacteria could get in. Conclusion The amount of mould went up as the water was increased to 20ml, before dropping with 30 and 40ml of water. Evaluation The two sets of results obtained were quite different, for example on the first experiment, the reading for after the decay was 31.6g(with 30ml of water), and while on the second experiment it was 84.5g. ...read more.

Conclusion

Also, if there was a draft, the rate of evaporation would have been speeded up, which could have explained decrease in mass, such as from 60.2g to 43.0g, in the first experiment, on the 40ml reading. Although the overall trend was the same in both experiments, that the decay initially larger as more water was added, then decay decreases again as water is increased further, the results were significantly different. This could be because of factors out of our control, such as the amount of oxygen present; it was impossible to measure, as we did not have the equipment to do this. Finally, it had to be assumed that the density of every piece of bread used was the same. This was probably not true, as some pieces of bread were taken from different slices, but within the same packet. For further work, I would investigate using a different method to asses the decay, such as find out the surface area of the bread, and finding out the amount infected, to give a percentage cover. Using transparent mm2 graph paper could do this. John Cummins ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Green Plants as Organisms essays

  1. How temperature affects the rate of photosynthesis.

    is shown by a very steep gradient by the curve between these two points. As the temperature increased from 45 oC to 55 oC, more and more enzyme controlled reactions start to slow down and from less enzyme substrate complexes (especially oxygen which was being measured).

  2. INVESTIGATING HOW TEMPERATURE AFFECTS THE

    Line graphs A line graph can be used to show relationships in data which are not immediately obvious from tables (Figure 4). When drawing any type of graph with axes, remember always to include: �an informative title �sensible scales on each axis, if appropriate �labels on both axes �units on both axes, if appropriate �a key.

  1. To investigate how motion of a dye droplet is affected by the temperature of ...

    Because of this I have decided to use a much thinner glass tube to minimize the current in the water column. DAY 4: A series of experiments have been carried out with the improved setup. A tube with a 9mm diameter is now used instead of the 3cm diameter one

  2. Investigation into the relationship between the density of fresh water shrimps in fleet brook ...

    Nitrogen is essential for the synthesis of protein and nucleotides in most living things. Nitrogen is recycled through the biosphere by the nitrogen cycle.7 Dead and decaying organic materials (in this case dead leaves) are broken down by denitrifying bacteria inhabiting the water.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work