Method
- Gather the required equipment and add pebbles to the water tank, so that the bottom of the tank is covered completely.
- Add 1.5 litres of distilled water to the tank, using a measuring cylinder. Measure and record the water’s temperature.
- Add 0.05g of potassium permanganate.
- Heat the water and observe the convection current as the temperature increases.
- At the same time, using another tank, repeat this procedure, making up 1.5 litres of acid rain (of pH 4) instead of the distilled water.
- By using the pH to concentration formula, we were able to work out the concentration of acid required to make pH, and found that this was 0.0001M hydrochloric acid.
- To make up 1.5 litres of this solution, 0.15ml of hydrochloric and 1499.85ml of water were required.
- Record the observations both solutions and record any differences that could be seen, paying special attention to the convection currents of each solution (compare the speed of the current).
Calculations
We used this calculation to work out the concentration of the solution needed to produce a pH4 solution of acid rain:
Concentration = 10 ^ (log 10 ^ -pH)M
= 10 ^ (log 10 ^ -4)M
= 10 ^ (-4 log 10)M
=10 ^ -4(1)M
=10^-4M
=0.0004M
Volume of 1M hydrochloric acid required = Concentration x Total volume of solution
= 0.0001M x 1500ml
=0.15ml
Vol. of distilled water required for this solution = Total volume – Volume of acid
=1500ml - 0.15ml
=1499.85ml
Conclusion
In conclusion, we found that the convection current for distilled water was slightly different from the current of acid rain. On the basis of our observations, the convection current for rain water moved slightly more quickly. This was evident when the tank containing the acid rain was put onto the hot plate, and it could be seen that its convection current was faster than distilled water’s. This is because it takes less time than the distilled water for the particles in acid rain to heat up and rise to the top, and also for cooler water particles to fall to the bottom of the container, hence creating a faster convection current.
This proved that our prediction was correct and that acid rain has a lower specific heat capacity than distilled water and that it is therefore a better conductor of heat than distilled water. The reason for rain water’s low specific heat capacity compared to that of distilled water is because rain water contains impurities making its properties slightly different from pure water. As well as change in the pH of the water these impurities also affect the bonding, decreasing its specific heat capacity. The reason as to why pure water’s specific heat capacity is so high is due its strong hydrogen bonds, which require high energy to be broken or pulled apart by being heated. Since, rain water contains impurities such sulphur, nitrogen and carbon, it has fewer hydrogen bonds, meaning that its temperature increases more readily once heated. This causes its particles to heat up more quickly, resulting in a faster convection current once it is heated.
Effects on the Environment
Acid rain has a negative affect on soil, and promotes poor plant growth. It also, over a substantial period of time, causes damage to some buildings and statues because of its slightly corrosive nature. It may also have an adverse effect on water-life, once it falls into lakes and rivers etc. Apart from the damage to the ecosystem, acid rain may also disrupt the Earth’s water currents. As we have discovered, through doing this experiment, that acid rain has a different convection current from normal water because of the numerous impurities that it contains. During hot weather, this may cause water with acid rain (such as in seas and rivers), to heat up quickly and effect the direction of the currents. This gradual increase in the temperature of the seas in the long-term may lead to melting the polar ice caps, and thus cause a rise in the water level, leading to flooding of low-lying lands.
A key factor which leads to acid rain is the sulphur, carbon and nitrogen emissions, which are released into the atmosphere when burning fossil fuels, into the atmosphere produced from factories etc. This pollution becomes dissolved in the Earth’s atmosphere and rains back down upon the Earth in the form of acid rain, having very negative results on the Earth’s environment, as I have mentioned already. To prevent these effects on the Earth’s atmosphere, we must strive to cut down on the emission of these gases which cause acid rain, and to find an alternative energy source to the burning of fossil fuels, which does not have such a negative effect on the Earth’s environment.
PART II – CHEMISTRY
Question: Does acid rain cause hardness in water?
Aim
To determine if acid rain causes hardness in water when it passes over calcium or magnesium ions and whether this hardness is perminant or temporary. (Pure distilled water will be tested with soap as a control).
Hypothesis
I has been predicted that acid rain will cause hardness in water. Acid rain is formed when the carbon dioxide in the atmosphere dissolves to produce a small amount of carbonic acid which is dissolved in the atmosphere’s precipitation, causing slight acidity. This acidic atmospheric precipitation falls back upon the Earth as acid rain:
H2O + CO2 → H2CO3
When this acid rain passes over calcium and magnesium rocks it dissolves the calcium and magnesium ions thus causing hardness in water:
CaCO3 + H2CO3 → Ca (HCO3)2
So when such a sample of (acidic) rain which has passed over calcium and magnesium rocks, this sample can be tested with soap in order to determine whether it is hard or not. Little or no lather will be given off if the sample is found to behard, because soap does not produce lather when reacted with samples of hard water.
The control( distilled water) will be used in order to ensure that the soap is working properly. The expected results for the control is that it will produce good lather when it is tested in soap because distilled water is not hard water and will actually interract with the soap, producing lather. If lather is not produced when the soap is in the presence of the distilled water then this result is anomalous and it shows eather that the soap has not worked properly or that the distilled water sample was conteminated. Distilled water does not dissolve calcium ions when it passes over these ions, and thus remains soft.
Once the hardness in rain water has been determined we will now test whether the hardness in the water is temporary or permanent. We will do this by boiling the sample of hard water and testing the sample with soap after it has been boiled. If leather produced after boiling the water this shows that the water only had temporary hardness; because the hardness of the water could be removed by boiling. However if the water did not produce leather when tested with soap after being boiled, this showed that the water was permanently hard and that this hardness can not be removed by boiling, and can be removed through the use of an ion exchange resin. I predict that if the calcium ions being dissolved in the rain water is calcium carbonate, then the water produced will be temporarily hard. This is because calcium carbonate is insoluble, meaning after being dissolved in the acid rain sample, and after boiling this sample, this calcium carbonate can be removed by boiling:
Ca(HCO3)2 → CaCO3 + CO2 + H2O
By boiling temporary hard water, the water’s softness and purity can be restored again, as the calcium ions will have been removed.
Apparatus
Method
- Collect the apparatus and pour 50ml of distilled water inside a beaker.
- Add 1g of calcium carbonate to the beaker.
- Pour 10ml of this solution into a test tube.
- Pour 50ml of dilute (0.0001M) hydrochloric acid inside another beaker. This is the concentration hydrochloric acid required to form an acidic solution of pH 4.
- Add 1g of the calcium carbonate to this beaker.
- Pour 10ml of this solution into another test tube.
- Test the contents of each test tube to see whether the sample is hard or soft.
- Repeat this procedure for the rain water, but before pouring the sample into the test tube and testing for hardness with soap, boil the sample.
- After boiling, add 10ml of the sample into a test tube and test the sample with soap, to determine whether the hardness was temporary or permanent.
Calculations:
Concentration = 10 ^ (log 10 ^ -pH)M
= 10 ^ (log 10 ^ -4)M
= 10 ^ (-4 log 10)M
=10 ^ -4(1)M
=10^-4M
=0.0004M
Volume of 1M hydrochloric acid required = Concentration x Total volume of solution
=0.0001M x 50ml
=0.005ml
Vol. of distilled water required for this solution = Total volume – Volume of acid
= 50ml – 0.005ml
= 49.995ml
Data Collection
Conclusion
From our results, it was evident that rain water became temporarily hard when calcium ions (in the form of calcium carbonate) were dissolved in it. This could be told because when rain water with the calcium carbonate contained in it, produced no lather when it was reacted, with soap. However when thsi sample of distilled water was boiled, then good lather was produced, meaning that the rain water became soft again once it was boiled. Therefore, rain water is temporarily hard. The initial hardness was caused because of the calcium ions that were dissolved within the dilute hydrochloric acid:
HCl + CaCO3 → Ca(HClO3)
This hardness, however, is only temporary, and the water sample can be made soft again by boiling. This is because calcium carbonate is insoluble in water, which a characteristic that is similar for virtually all carbnates. Therefore, once boiled, it can be removed easily from the water. This means that calcium carbonate only causes temporary hardness once it is dissolved in rain water. However, when acid rain passes over rocks such as gypsum and dissolve calcium sulphate (which is soluble in water) permanently hard water is caused, which can only be reversed by the use of an ion exchange resin or by the addition of sodium carbonate. In industry, boiling is not a preferred way of removing temporary hardness as is a very expensive method which wastes too much energy. So, in industry either adding sodium carbonate or using an ion exchange resin is preferred.
The distilled water was used as a control. As predicted this poor water was not hard and produced no lather when reacted with soap before and after being boiled.
Our findings confirm that acid rain does cause hardness in water when calcium ions are dissolved in it, and that the type of hardness caused (temporary or permanent) depends on the type of calcium or magnesium ion that is dissolved in it.
In a global aspect, hard water can cause limescale and block pipes, making them inefficient. It also wastes soap, as no lather can be produced in the presence of hard water, as we have found in this experiment. The other problems that the Earth faces because of acid rain, other than the fact that it causes hardness in water, is that it has a negative effect on wildlife, as it can kill plant and animal life, and causes acidic soil and water (in lakes, rivers etc) and damages buildings.
PART III – BIOLOGY
Question: Does carbon dioxide affect plant growth?
Aim
To determine the effects that carbon dioxide has on the growth of plants. In this experiment, we are investigating the effect of carbon dioxide on the growth of beans, specifically. It is also part of our aim to confirm that carbon dioxide really is a greenhouse gas.
Hypothesis
I predict that the plant inside the container with the carbon dioxide will grow poorly, since the atmosphere within the container will contain a high proportion of carbon dioxide, and a low proportion of oxygen (which is the gas required for respiration). Because of this, the growing beans will not be able to respire and grow, and could even die within a few days. This is the formula for respiration:
6O2 + C6H12O6 → 6CO2 + 6H2O
Plant seeds can not photosynthesise during their growth, since they have no leaves, which is the main site where photosynthesis occurs. Since they have no leaves, they have little or no palisade cells containing chloroplasts, which contain the green pigment chlorophyll. Chlorophyll is the pigment which absorbs light and uses it for photosynthesis. Without this, photosynthesis cannot occur as light cannot be absorbed into the leaf without it. This is the equation for photosynthesis:
6CO2 + 6H2O → C6H12O6 + 6O2
Because of the increased amount of carbon dioxide inside the beaker and the early stage of life that the plant is in, it will neither be able to respire nor photosynthesise easily. For this reason, the plant will have poor growth and will eventually die because of its inability to get its nutrients required for survival.
Other beans will be placed in a container with no carbon dioxide being produced inside it, in order to be used as a control and to form a comparison between the lengths of these plant and the lengths of the plants in the container with the carbon dioxide. Since, this container will contain normal levels of oxygen and carbon dioxide, the plant will be able to respire easily, and will grow at a normal rate, producing a long shoot. The beans in his container will still be alive by the end of our experiment and will benefit from the favourable conditions.
Finally, since we will be recording the day-to-day temperature, I predict that the temperature inside the container without carbon dioxide will remain constant throughout our experiment, whereas the temperature inside the container with the carbon dioxide will increase as the days progress, because carbon dioxide is a greenhouse gas. This means that carbon dioxide will allow heat energy from the light source to enter the container, but will not allow it to leave, and will reflect it back inside the container, which will eventually cause a gradual increase in temperature, as more heat builds up. This is exactly what is happening in the world’s atmosphere today as the heat energy from the Sun becomes trapped in the atmosphere since the carbon dioxide has allowed it to enter, but will not allow it to leave.
Apparatus
Method
Making Carbon Dioxide:
1) Collect apparatus.
2) Put 30 ml of calcium carbonate in a 50 ml beaker.
3) By the use of the measuring cylinder, collect 30 ml of sulphuric acid and place it into another
50 ml beaker.
4) Pour the acid onto the
5) Do the flame test and see whether or not you gathered carbon dioxide (if the splint goes out
carbon dioxide is formed).
Testing Carbon Dioxide’s Effect on Plants:
1) Collect apparatus.
2) Gather 2 evaporating dishes and place cotton in them.
3) Place 2 beans in each evaporating dish and pour distilled water on them.
- Place these evaporating dishes in the bigger ones.
- Place a thermometer in each of them and cover in with a 700 ml beaker.
- For one of the containers, react calcium carbonate with sulphuric acid, in order to produce carbon dioxide.
- Observe any differences in the appearance and length for both containers every day, and record any changes in temperature.
Results
Data collection for the container without carbon dioxide being produced in it:
Data collection for the container with carbon dioxide being produced in it:
Analysing Data
Temperature change:
Change in beans’ average length:
Conclusion
From our results, it was evident that the beans inside the container without the carbon dioxide being produced everyday grew much more than the beans inside the container in which carbon dioxide was being produced. This was because the beans inside the container with the excess of carbon dioxide were unable to respire properly, because of the lack of oxygen inside the container. These adverse conditions actually killed the beans, which stopped growing after day 2, and turned into an unhealthy, mouldy colour. On the other hand, the beans inside the other container which contained normal conditions grew normally and one of them even grew a shoot of length 8.4cm, which was about 17 times the growth inside the other container. The plants inside this container, without much carbon dioxide grew more in days 1-2 than the plants in the container with the carbon dioxide grew for the entire experiment. The data shows clearly just how much difference there was in the growth between the growth of the beans inside the container with the carbon dioxide being produced and the growth of the beans inside the other, control container. Our findings, show that carbon dioxide really does have an effect on plant growth, and has the ability to (when in high concentration), to stop plant growth completely (as was seen in this experiment).
This experiment highlights just what a danger a greenhouse gas like carbon dioxide is to the atmosphere in high concentrations, and what is more worrying is that the amount of carbon dioxide and other harmful greenhouse gases are gradually increasing in the atmosphere. Even in low concentrations, carbon dioxide and other polluting gases can be held accountable for the increasing number of human diseases such as asthma. It is also a great danger to plants and can be very harmful to them, as clearly demonstrated by this experiment. As, we have also learned from this experiment, it also traps heat rays from the Sun, prevents it from re-entering space and keeps it within the Earth’s atmosphere, causing global warming (the greenhouse effect). Another problem arising from excess carbon dioxide being present in the atmosphere is that it causes acid rain once the carbon dioxide gets dissolved in atmospheric precipitation to form dilute carbonic acid (which is acid rain). Acid rain affects the pHs of soil, lakes, rivers etc. and has a negative effect on architectural structures due to its corrosive nature. This experiment clearly emphasizes just how important it is for the world to reduce these carbon dioxide emissions, and some of the long-term problems that may arise if carbon dioxide continues to be released into the atmosphere at the rate that it is being produced today.
