Fair test: to make the experiment a fair one I will control the amount of water, temperature and concentration of the acid. I will use 20 cress seeds to get reliable set of results for each dilution.
Safety: to make the experiment I will follow these rules:
- Always wear safety glasses because of the acid.
- Wear the lab coat all the time in case the acid spills on you.
- Don’t eat, drink or run in the lab.
- Don’t throw objects because you could hurt someone.
Scientific knowledge:
Acid rain the name suggests that acid rain is just rain, which is acidic. The rain becomes acidic because of gases which dissolve in the rain water to from various acids. Rain is naturally slightly acidic because of the carbon dioxide dissolved in it (which comes from animals breathing), and to a lesser extent from chlorine (which is derived from the salt in the sea). This gives rain a pH of around 5.0, and in some parts of the world it can be as low as 4.0 (this is typical around volcanoes, where the sulphur dioxide and hydrogen sulphide form sulphuric acid in the rain).
Most of the stuff inside the seed coat of a cress seed is endosperm. It is full of compounds that will help the plant grow and be those cotyledon leaves that you first see after germination. Much of the material here can be lost and the plant survives. The effect does the acid is has on the very tiny and very specialised part, the embryo, where cells are already formed and where most of the initial merits cells are. These merits cells are the ones that do all the dividing. If cell division does not happen, the plant does not grow and eventually it will die. The acidity is has an effect on those cells. Membranes keep cells separate from each other; these membranes keep areas isolated from each other so that reactions in one area don't interfere with reactions in another. Water and some other things such as hydrogen pass freely though the membranes, but most things are only let in through expenditures of energy or as a result of a pH gradient. The hydrogen’s in an acid (like sulphuric) disrupt the pH gradient. The cell must work overtime to deal with the additional hydrogens and processes such as photosynthesis and respiration are disrupted, which at first slows growth and may eventually result cell death.
Once the hydrogens are gone from the sulphuric acid, the sulphate that is left will bind with minerals and nutrients in the seed and remove them from use by the plant. There are many other things that go on as a result of the presence of sulphuric acid in the plant, but the above are some of the most obvious and important.
Dilution series: to make the dilution a series I will use this table to help. To make a 0.009 molarity of acid I will take 9cm³ of acid and 1cm³ of distilled water. Below is the table for dilution series:
Result table:
Results on first day:
Results on second day:
Results on third day:
Total length:
Average length:
Percentage germination of last day:
Conclusion & analysis: my prediction was right that stronger the concentration acid the smaller the length of germination. I can see that by looking at my graphs of total length of germination graph and average length of germination at different concentrations of acid, at 0 concentration (distilled water) the length of concentration of germination is the longest.
My other prediction was that stronger the concentration of acid the fever seeds will germinate was also right. In my percentage germination graph I can see that stronger the concentration of acid the fever seeds germinated.
Evaluation: I can see that I had less seeds germination at water than at the concentration of 0.001, this could had been due to the quality of seeds I used. If I have a chance again to this experiment I will use good quality of seeds and make sure they are not damage. I would also like to use different types of seeds and acid, which will help me to see the connection between the acids and seeds. I would also like to see how the temperature, water and oxygen will effect the germination of seeds.
