Calcium carbonate

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.

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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.