Time table French :4 hours Math :5 hours History : 3 hours Biology : 4 hours Chemistry and physic : 4 ½ hours German : 2 hours English : 2 hours Sport : 2 hours « TPE »: to work on the project « Comenius » : 2 hours score : 28 ½ hours we don't work on Wednesday afternoon sometimes we have school from 8 am to 6 pm we have a 1hour-break for lunch at 11am or 12 am
School system Kinder Garten 3 years old 6 years old 11 years old 16 years old 6 ème 5 ème 4 ème 3 èm e 2 nde 1 ère TERMINALETERMINALE « Collège »« Lycée » Primary school CP CE1 CE2 CM1 CM2 « Brevet des collèges » « BAC » EXAM :
Troyes, a town of art and history (125,000 inhab.)
Troyes is known for its textile industry It is famous for its factory outlets where you can buy famous brands at good prices.
Normally, the rain has a pH of 5.6. But sometimes it can be 1.5 ! What can change the acidity of the rain?
Natural causes : they represent less than 0.1 billion tons of gas - The air contains approximately 0,03% of CO 2, which explains the low acidity of rainwater (pH = 5.6) -Forest fires - NO 2 released by the lightning - CO 2 produced by the bacteria of the ground. - Aggravation factor : because of the wind, the clouds can move 500 km per day.
- CO 2 and SO 2 produced by the volcanoes Example: this volcano, "Kawah Idjen" has a lake of 38 million m 3 of sulphuric acid (island of Java, in Indonesia)
- Nitric oxide (NO) in exhaust fumes - Nitrogen dioxide (NO 2 ) - NO 2 due to the production of electricity and weldings - Use of explosives - Industries use coal, oil or fuels rich in sulphur, they produce SO 2 which is transformed into sulphuric acid (H 2 SO 4 ). - Cast iron - Wood transformed into paper - Incineration of waste - Aerosols Human causes : they represent more than 6 billion tons of gas !
The most polluting country : the USA with more than 17 million tons of SO 2 in 1996 ; 21 million tons of NO 2 The least polluting countries: Sweden, Norway (both polluted by the United Kingdom), Switzerland, Austria. Origins of NO 2 emissions in the United Kingdom in 1998. 1,753,000 tons (NO 2 and NO) Origins of SO 2 emissions in the United Kingdom in 1998. 1,615, 000 tons
Our experiments : description, results and interpretation.
I. Experiments on gas potentially responsible for acidity of the rain 1) Carbon dioxide : CO 2 CO 2 + H 2 O = HCO 3 - + H + 2) Nitrogen dioxide : NO 2 2 NO + O 2 = 2 NO 2 3 NO 2 + H 2 O = 2 HNO 3 + NO 3) Sulphur dioxide : SO 3 2 SO 2 + O 2 = 2 SO 3 SO 3 + H 2 O = H 2 SO 4
1) Carbon dioxide Question : Can CO 2 be responsible for the high acidity of the rain (pH=1.5)? We carried out an experiment the purpose of which is to saturate a small quantity of distilled water with CO 2. Then we measured the pH. For that, we put sodium hydrogenocarbonate (NaHCO 3 ) in a bottle with hydrochloric acid (HCl). As a result, there was an emission of CO 2.
After taking enough gas while leaving distilled water in the bottle, we stopped the reaction and we shook the bottle to dissolve CO 2 in water. Then we measured the pH of the solution obtained : pH = 4. The initial pH of water was 4.6. Thus we deduced that CO 2 is not responsible for the high acidity of the rain.
2) Nitrogen dioxide Question : Can NO 2 be responsible for the high acidity of the rain (pH=1.5)? We carried out an experiment the purpose of which was to dissolve a great quantity of NO 2 in a little quantity of distilled water. Then we measured the pH. For that we put pieces of copper and nitric acid (HNO 3 ) in a bottle. As a consequence, NO 2 was emitted.
After taking enough gas, we added distilled water in the bottle. We closed it and we shook to dissolve NO 2 in water. Then we measured the pH of the solution obtained : pH = 1.2. The initial pH of water was 5.1. Thus we deduced that NO 2 could be a factor responsible for the high acidity of the rain.
3) Sulphur dioxide Sulphur dioxide is very water soluble, it dissolves in the small water droplets of the air, thanks to the wind. Sulphur dioxide is also responsible for the acidity of the rain. But we did not make an experiment to prove it.
II. Water analysis 1) Analysis of rainwater 2) Experiments on distilled water
1) Analysis of rainwater We sampled rainwater during each downpour (approximately 15 samples). We measured the pH of each sample. The results showed us that our rain is only slightly acid. Indeed the pH is between 5.7 and 7.7. We also measured conductivity because it varies with the impurities. We carried out two other tests on these water samples.
The first one consisted in putting rainwater in a test tube. We added lime water to detect CO 2. But we did not observe any precipitate : so there is not much dissolved CO 2 in rainwater. The second experiment consisted in testing the nitrates possibly present in water. But we did not find nitrates in water, the strips did not react. We deduced that in our area the gases responsible for the high acidity of the rain are only very slightly present in the air.
2) Experiments on distilled water In order to collect gas from the air, we put a recipient filled with distilled water outside, protected from rain, for a week.We measured pH at the beginning and compared it to the end. pH at the beginning = 5 pH at the end = 6 Those results show that no gas responsible for acid rain is present in the air above Troyes.
Acid rain Soil Faun Forests Lakes Health Monuments
Forest They are more or less affected according to their geographical site. The forest undergo direct and indirect consequences.
Direct consequences In the presence of photo-oxidants, the leaves lose their waxy coating and thus become more exposed to diseases, their color changes.
Indirect effects Acid rain attacks the trees indirectly and : -weakens when damages the leaves, -limits the elements available, -poisons with toxic substances slowly released by the ground. If the ground does not manage to neutralize acidity the trees will be the first touched.
Limiting air pollution : - by using cars with catalytic converter - by using electric cars & solar power cars -by equipping the chimneys of the factories with purifiers to limit the emission of nitrogen Moreover,each one of us can also do something to reduce the development of the acid rains.
At home: -reducing water consumption -buying electric appliances which consume little energy -using less heating in winter -using less air-conditioning in summer. Transport: -riding bikes or walking as often as possible -using a less polluting gasoline.
Conclusion A lot of countries try to reduce their gas emission because they feel concerned by the acid rain problem ; for several countries progress is considerable what lets us think that the increase of acid rain can be slowed down, even stopped !!!!!