Soil Type Investigation

Soil Type Investigation
The aim of the experiment is to establish what types of soil holds the most water and to see if changing a certain variable such as the ph value of the water has any effect on how much water each type of soil will hold. Background Information Many factors might affect the absorbency of soil, some affecting only certain types of soil in particular. For example the obvious influences such as the amount of soil and the amount of water added to it will certainly limit how much water the soil can hold and the amount able to pass through. However, there are also other less apparent aspects that might also have an effect on the limit of water different soils can hold. For example the size of the soil particles might have an influence because if the soil is in large chunks that leaves gaps in between them then the water may just filter straight through so little is absorbed by the soil. On the other hand, if the soil is in a fine grained sand this might trap the water because there is little space between the particles causing a lot to be absorbed
Foreign bodies in the soil such as debris, small pieces of litter, chunks of clay or rocks and even the amount of glass wool used may also effect the absorbency by either blocking the funnel so that the outlet is blocked causing the water to be trapped in the filter under the soil with soil floating on top ? though the water is not actually absorbed, or, if the outlet is not blocked helping the water to drain easily through the soil so that it hold less. Another factor which may effect it is the temperature of the water, according to particle theory, the water particles have more energy and move faster if the temperature is higher causing more particles from the surface to escape into the air as they evaporate, thus meaning that less is held in the soil because it is constantly evaporating at a quicker rate. What is more, the water which does actually come through the beaker may also evaporate before it is measured so again distorting the results. And at the other extreme if the water is cold or near freezing, frozen particles within it will not be able to be absorbed into the soil as they are solid and to large meaning the soil holds less, however, they also won?t be able to pass through the funnel either. This means that temperatures at the extremes for water (0 or 100 degrees Celsius) are quite difficult variables to measure. Micro organisms in the soil such as small living insects or parts of plant stems etc. may absorb some of the water themselves making it appear that more has been held within the soil, again affecting its recorded absorbency. Another factor which would be interesting to see if it had any effect on the soil would be the ph value of the water added, as, possibly if the water was very acidic or alkaline this may have an effect on how quickly it evaporates or even possibly if it reacts with any of the properties in the soil causing a chemical reaction to take place so that new products are formed and maybe even gases given off which will reduce the amount of water passing through the funnel. It would be another test to see if acid or alkaline react the best with different sorts of soil and then compare the results to how they effect the absorbency. Finally, the salt content of the soil may also have some effects whether it is because large salt crystals help filter the water, fined grained salt traps it or even that the salt gets absorbed into the water thus reducing the overall mass of the soil meaning that less water can be held within it, plus the fact that the amount of salts dissolved in the water affect its movement through the soil which may mean that it will run quicker through a larger mass or on the other hand get trapped more easily in spaces, both affecting the water passing through and final result for the soil absorbency. Prediction and Hypothesis This prediction is going to be based on two different variable which are the different types of soil: clay, sandy, woodland and peaty and the different ph values of the water added: strongly acidic, neutral and strongly alkaline which means that their will be 12 results three for each type of soil. The prediction is that the clay soil will absorb the most water because clay has a large surface area and is very thick allowing it to take up large amounts of water by causing some water to cling to it (adhesion.) Clay will also swell as it absorbs water because the particles in it are very fine as a result making its water capacity higher. After clay, peaty soil will most likely hold the largest amount of water because it is also finely grained yet more compact than clay and not as malleable and stretchy. Peat also contains a lot of decomposing mass and organic matter as well as moss which may help it to hold more water if the matter absorbs some of it. Third, after peat will be the sandy soil because although the grains are very fine which might cause some water to be held, the grains don?t swell like peat and clay to form slippery reservoirs and usually the water just filters through even though it can take a long period of time. However, sand usually does contains a lot of salt which can affect the movement of the water causing it to move more slowly through the grains which may mean that less gets through in the time space allocated for the experiment. And, lastly it is predicted that woodland soil, which in England is known as heavy soil because it is rough and compacted, will hold the least water. Woodland soil usually contains fragments of roots and small rocks mixed with fine grained compost which means it holds less water as the water usually drains through the larger pieces. However, some woodland soil can contain decaying matter that can help to trap water in gaps between the layers. The other part of the prediction is whether the ph values of the water added to the different soils affects the absorbency. It is predicted that a neutral solution will cause the highest amounts of water to be absorbed mostly in clay, then peat, then sandy and finally woodland ensuring that the properties of the different types of soils above still apply. It is probable that making the water alkaline will have more affect than making it acidic so water with an alkaline solution in it will cause the soil to absorb more water. This prediction is based on the fact that many soils are slightly acidic anyway and so is rain water which has dissolved sulphur dioxide in it so most likely acidic water will act like it normally does as good as, if not better than neutral water because most water absorbed into soils is slightly acidic anyway. It is predicted that it may seem that an alkaline solution has caused more water to be absorbed but actually a chemical reaction will take place between the alkali and the minerals in soil which are usually acidic causing a molecular change and different compounds to be formed and possibly even a gas being given off so less water will get through the soil thus it seeming that more has been absorbed when maybe it hasn?t, it has just been given off or chemically changed. Furthermore if the soil is quite acidic such as peat maybe a neutralization reaction will take place when the water is added again giving off a gas and making it seem like more has been absorbed when it hasn?t. Apparatus List Ø 4 Filter funnels Ø 12 small pieces of glass wool (0.5g each) Ø 4 beakers 47ml full of water plus 1 pipette full of hydrochloric acid (3ml) Ø 4 beakers 47ml full of water plus 1 pipette full of lime water - alkaline (3ml) Ø 4 beakers 50ml full of neutral water (ph 7) Ø 3 samples of peaty soil (15g each) Ø 3 samples of sandy soil (15g each) Ø 3 samples of woodland soil (15g each) Ø 3 samples of clay soil (15g each) Ø measuring cylinders (50cm3) Ø Stop watch Pre Test Type of Soil Amount of water absorbed by the soil (cm3) or (ml) Absorbency rating (1- 4) best to worst Clay 14 1st Peaty 10 2nd Woodland 7 4th Sandy 11 3rd [image] The pre test enabled us to get used to using the equipment needed for the actual investigation and the quantities of the soil samples we will need. During the pre test many problems arose such as the water not seeping through because of too much glass wool, too much soil causing the filter to over flow when the water was added and the whole experiment taking too long for the water to stop draining through. So consequently as a result of the pre test it is decided that their will be a measured amount of glass wool put into the funnels set at 0.5g. To avoid the problem of the filter funnel over flowing and because some soils are more denser and weigh more the amount of soil to be used each time has been set at 15g so that their masses are all equal for fairer results. Doing the pre - test we also discovered that the time taken to do the experiment was just too long and it has been decided that the measure of the amount of water which has passed through will be collected for each test after a time limit of 2 minutes, to reduce the whole time of the experiment. Furthermore, as we chose to investigate the effects of having water at different ph levels as well as different types of soil we made a decision to add to the water, a strong acid (about ph 1 - 2), a neutral solution (about ph 7) and a strong alkaline about (ph 12 - 14) to be tested with each sample of soil seperately. The acid selected is hydrochloric acid and the alkaline, lime water as they are both strong concentrated solutions, and finally, for the neutral water we are going to use just ordinary tap water. Diagram Plan Gather all the equipment mentioned above in the apparatus list, making sure that they are working efficiently and that beakers are not contaminated with other substances. ? Set out the four 50cm3-measuring cylinder and place a filter funnel in each one. ? Weigh four small pieces of glass wool to about 0.5g and put one at the bottom of each funnel covering the tube opening. ? Get four large containers and fill them with all the different types of soil. From this measure 15g of each type of soil and put them in the separate filter funnels ? do not mix soil types. ? Fill small four beakers with about 47g of normal tap water and then add 3ml or one pipette full of hydrochloric acid. ? Pour one beaker of acid into each of the filter funnels at the same time remember to get someone to start the stop watch the second the liquid goes into the funnel. ? Wait 2 minutes, making sure that 50ml of the acidic water has been added to each of the soils. ? After 2 minutes take the funnels out of the measuring cylinders, wash the soil away and clean the funnel so that it is not contaminated. Also clean out the beakers with the acidic water in so that they can be used again. ? Record the amount of water that has passed through for each of the soil and take this amount away from 50ml to get the amount that the soil has absorbed. Afterward clan out the measuring cylinders as well. ? Next, set up the experiment from the start again using fresh soil samples, fresh glass wool and clean equipment. ? This time use alkaline water by adding 3ml or one pipette full of limewater to the four beakers 47 ml full of regular tap water. ? Repeat the experiment as above for alkaline water and neutral water remembering to clean out all the equipment after each one and use new sample of soil and glass wool to avoid contamination. ? Repeat the whole experiment at least three time so that an accurate average can be taken in order to display the results easily, recording the findings after each test and any unexpected results. Method For the method, the plan was followed almost exactly expect that we discovered that 0.5g off glass wool was still far to much and would block all water from draining through the funnel. It was decided that the amount of glass wool for each test would have to change and was finally set at 0.05g instead, a tenth of the original size ensuring that some water would be able to pas through for measuring yet no soil particles. We also discovered after doing the experiment once that 2 minutes was not long enough for the all water to drain through as much of it seem to build up on the top of the soil. Consequently we decided that we would give it and extra 30 seconds setting the time at 2 minutes 30 and this seemed to work very well with the majority of the water either passing through the funnel or being absorbed into the soil. This improved the experiment by making it more worthwhile and actually gave us some results to analyse and measure. Fair Test and Safety Precautions To ensure that the test is fair it has already been decided that between each test all the equipment will be washed and new sample of soil and glass wool used each time as not to contaminate the containers and distort the results. Equal amounts of soil used in the filters as well as water and acid added to the beakers has been set as controlled quantities that will be used throughout the test ? 15g of soil, 47ml of water with 3ml (A pipette full) of acid and alkali added each time. The time of each test has also been managed and was set at 2 minutes 30 ensuring that each individual experiment is allowed the same time limit for fairer results. As a safety precaution safety goggles should be worn when handling the acids and alkalis and great care should be taken at all times to reduce the risk of injury because acids are harmful, especially to the skin. All equipment should be set up at a reasonable distance from the edge of the desk to reduce spillage and accidents especially if corrosive substances are being used. Finally hands need to be washed with clean water after the experiment just in case a harmful substance has got onto the skin unnoticed and because germs can often breed in soil samples, again to reduce the risk of illness or injury. Results Table Soil type Ph of the water added Absorbency of soil (cm3) 1st Test 2nd Test 3rd Test Average Clay Acidic (ph 1 -2) 44 47 41 44 Alkaline (ph 12 ? 14) 34 32 38 34.7 Neutral (ph7) 45 40 42 42.3 Peaty Acidic (ph 1 -2) 40 39 39 39.3 Alkaline (ph 12 ? 14) 20 26 27 24.3 Neutral (ph7) 26 21 23 23.3 Sandy Acidic (ph 1 -2) 12 17 15 14.7 Alkaline (ph 12 ? 14) 8 6 9 7.7 Neutral (ph7) 3 4 2 3 Woodland Acidic (ph 1 -2) 13 15 11 13 Alkaline (ph 12 ? 14) 12 10 12 11.3 Neutral (ph7) 11 5 13 9.7 Analysis ==== The graph shows us that overall clay held the most water with 121ml out of the possible 150ml being absorbed, after clay came peaty which also absorbed much of the water, 86ml just under 3/5 of the total amount. Both these results followed the prediction with clay absorbing the most and then peaty. It was predicted that sandy would held the next greatest amount and then woodland the least. However, the results showed otherwise with the total absorption for sandy soil being over double the absorption for woodland soil. It was predicted that clay would hold the most soil because it has a large surface area allowing water to be absorbed at a faster rate, especially evident because the investigation took place on a time limit. Clay is also usually found in thick fragments that cause adhesion and greater depth for the water to penetrate and run into. The main quality of clay that made it the top for the prediction is the fact that it swells in water, resulting in a higher water capacity unlike soils with large grains that tend to not well as much as those with fine grains such as clay. Peaty soil was chosen to be the next type of soil to hold the greatest amount of water after clay for many of the same reasons; again it is finely grained resulting in a higher water capacity because it can swell easily. However peaty was after clay as it is usually more compacted meaning water can not so freely seep through and also because it is not as malleable or stretchy both aspects that increase a soils? water capacity. The fact that peat is usually found to hold decaying matter or organic matter helps support the reasons why it was predicted to hold greater amounts of water as organic matter especially often absorbs much water for life purposes e.g. respiration. The prediction was proved wrong after this point as the results show woodland soil to hold more water than sandy. Sandy was originally thought to hold the most because it like peaty and clay is finely grained although it does not have the qualities to hold water but instead just filters it, it was predicted that the water would take a long time to filter through therefore not within the short time during the experiment so consequently in the prediction it was thought that not much water would get through in the time allowed so sandy was placed before woodland. The experiment proved this wrong as observations noted showed that the water filtered through the sandy soil quicker than expected resulting in only 15.4ml of water being absorbed in total. This may have been to the fact that only a small quantity of the sand was used or that it was not as compacted as it is naturally found due to being constantly turned and moved around when usually sandy soil leaches water to the sub soil underneath. It is also possible that the salt content in the soil was high resulting in a lot of the salt being dissolved into the stream of water and cutting a channel within the soil for the water to flow through so less is absorbed. These are all random errors that could have not been realised without doing the experiment and are just down to the actual sand present in the soil used in the experiment. The possible reason why woodland proved to hold more water, more than double that of sandy maybe because it was predicted to contain large fragments of roots, small rocks and other foreign bodies as well as some fine grained soil. When the actual experiment was done however, the woodland soil contained hardly any other fragments and to the touch it did not vary much from peaty - quite spongy and malleable, not rough and rocky at all. The prediction focused on the fact that rocks and other fragments thought to be present in the soil would help the water to drain through by creating channels, much like plants are watered in places where drought is common. As the woodland soil appeared to have little to none of the qualities already thought this made the prediction less accurate. Again these are all random errors caused by the conditions and materials used, yet, other systematic errors may have also occurred which may help to explain some results. Even though the glass wool used in the funnels was precisely measured the way in which it was put in affected the experiment as well as the way the soil was added on top. Sometimes the glass wool slipped down the this funnel tube probably under the weight of the water and soil causing a complete blockage although this did not seem to distort the results too much. The measuring device used was not very accurate meaning results could only be measured to the nearest millimetre and not fractions of millimetres plus the fact that it proved difficult to start the clock whilst pouring in four liquids at the same time, as a result extra help was needed. The other variable that needs to be dealt with is the changes made to the ph of the water in the experiment to see if this has any effect of the different soils absorbency. It was found that out of the total 200ml of neutral water added only 78.3ml were absorbed by the soils, 87.3 ml of alkaline water and 91.7 ml of acidic water were also absorbed again out of 200ml each time. It is possible that overall the most water absorbed was acidic because most likely the soil would be acidic due to acidic rain caused by sulphur dioxide being absorbed into it. Whilst this water probably behaved in the usual way as rain water even though the acid content in rain water is much weaker the alkaline and neutral water may have reacted with the acidic water may be causing chemical changes within the soil and possibly resulting in new compounds being formed such as salts which cause water to behave in strange ways usually channelling it and meaning that more seeped through so less was held in the soils. Sandy soil usually has high quantities of sodium chloride dissolved in it, when the acidic water was added to this more was dissolved than neutral or alkaline, this may be due to the fact that salt does not dissolve well in hydrochloric acid which is the acid use to make acidic water. Consequently, this caused no channels to be dug so the water did not move straggly due to the salt particles dissolving in and therefore more was held within the soil. Peaty soil usually has quite a high acid content as it is found in the acid water bogs where it holds vast quantities of water. In the experiment the peaty soil made no reaction with the acidic water so no gases was given off or channels made through chemical reactions or dissolved therefore the peat held the most acidic water just as it does naturally. Peat held about equal amount of neutral and alkaline water and during both these tests small channels could be seen down the sides of the funnels indicating that a chemical reaction had taken place and given a reason as to why more water was filtered through and not absorbed. With woodland soil roughly the same amount of water was absorbed with each test ? acidic, alkaline and neutral ? and this was not very much. It is possible that no reaction occurred between the soil and any of the water samples as the particles in soil test usually to just be organic matter. It is more probably due to the physical properties of the woodland soil mentioned earlier why not very much water was held. Finally, the clay soil did not follow the other patterns and when acidic water was added to the soil it held the least instead of the predicted most. It was thought that because clay contains calcium carbonate, which is an alkaline salt that it would dissolve in the water and cause more to be filtered through. This did not occurred possibly suggesting that there was little to none calcium carbonate present in the soil which is a random error. Other systematic errors may have occurred such as the strength of the solutions being different or possibly even contaminations although great lengths were gone to in order to prevent this. Evaluation The method used was fairly accurate showing a good range in results and mostly following a logical, predicted pattern. There was also sufficient data to plot graphs from, take averages and thoroughly analyse. However, many random problems occurred which would need to be thoroughly checked such as contamination of soil types etc. A possible way around this is to collect your own resources and not pre collected one. Systematic errors also occurred which mean the plan needs to be more thorough and possibly more care taken as the risk of contamination was high in this investigation as not only was there different soil types but also different chemicals with greatly varying ph values essential for the experiment. The anomalous results yet this was expected and due to random errors that could not have been foreseen, possible reasons are the content of chemicals I the soil which were expected to be different such as the calcium carbonate content in the clay soil and the sodium chloride in the sandy soil. The physical properties also somewhat varied from what expected such as woodland proving to be fine grained and malleable when it was predicted to be rocky containing various fragments. Possibly the only way to combat this would be to elongate the method and make sure the soil samples were what expected maybe by individual collection of them. Overall however, the results were reliable yet the equipment and resources used not as accurate as expected, yet this can not be helped. Some results seemed less reliable not following regular patterns and often being of extreme quantities either low or high, again this could have been the result of contamination, in accurate equipment, unreliable soil samples ? not following the characteristics of these samples found naturally or just systematic errors e.g. the result of being careless, spillage, inaccurate measuring and timing or accidental contamination due to problem with cleaning the equipment which had to be done many times after each test. Possibly the experiment could be done again yet with less data to collect or a least less in the time given meaning that more care can be taken with cleaning apparatus resulting in less contamination, difficulties and overall more accurate results. Further work may include testing the soil samples to more accurate degrees of ph values instead of just acidic, alkaline and neutral and possibly more samples e.g. ph values from 1 ? 14 and not just the extremes and central. On trypes of chemical could be tested more thoroughly with a certain types of soil e.g acidic water with only clay soil, larger samples could be used and possibly a rain gauge could be set up in the ground too see the average amount of rain that falls on the soil and then this amount could be used in the lab for more real life like results. Possibly soil types from different areas could be tested with water of different ph?s to give a more accurate picture of soil absorbency across the British isles with possible explanations to the results found based on chemicals present, the vegetation growing there, the amount of rain fall, the types of rock its is found near, the contour of the land and the properties of the soil. An investigation such as this would certainly help agriculture and farming giving those who ork with the land ideas where soil would be fertile, where it would be barren and why. It would help biologists discover reasons for certain habitats and geographers possible reasons for landforms and how the landscape has been shaped etc.

Soil Type Investigation 7.2 of 10 on the basis of 4206 Review.