Exam of units 0 (inorganic nomenclature) and 1 (scientific activity) of 3º ESO B. Name...

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1 Exam of units 0 (inorganic nomenclature) and 1 (scientific activity) of 3º ESO B Name.... Exercise 1 Formulate or name: 1. fluorine (difluorine) 2. H 2 Se 3. manganese trihydroxide 4. TeO 5. Pentaoxygen dibromide 6. CaCl 2 7. Iron (III) iodide (iron triiodide) 8. Ag 2 O 2 9. Sodium carbonate 10. Chromium (II) hydride (chromium dihydride) Exercise 2 a) Hypothesis (definition). False hypothesis and true hypothesis. b) Experimentation. Explain. Why, when studying how a variable affects the results of an experiment, all the other variables must remain constant? Exercise 3 Steps of the scientific method. Brief definition of each one. Exercise 4 Explain the experiment we did in the laboratory last week (the pendulum and its period). Explain the different variables we studied and if these variables affect the period of the pendulum or not. Due to lack of time, the data that you obtained in the laboratory probably has a lot of errors. If you had more time to do this experiment, what would you do to minimize the errors of the measurements? Exercise 5 Change the following units using conversion factors. Express the final result in scientific notation rounding off to two decimals dg/cm 3 to hg/m dam/min to mm/s g to g ps to ns dm 3 /h to ml/s (Remember 1 ml=1 cm 3 ) kg m/s to g cm/h

2 Exercise 6 A car is stopped at a red traffic light. When it turns green, it starts moving and we can measure the space it travels after some seconds: time (s) space (m) Represent the data. 2. Write its mathematical function. 3. What is the space the car has travelled after 3 seconds? 4. What is the time the car needs to travel 100 m?

3 Exercise 7 Antoine-Laurent Lavoisier, a meticulous experimenter, revolutionized chemistry. He established, among other things, the law of conservation of mass. He experimented with many chemical reactions (in chemical reactions some substances, the reagents, are transformed into different substances, the products) and proved that in a chemical reaction mass is neither created nor destroyed, it is only transformed. Therefore, the mass of the reagents is always equal to the mass of the products that are obtained. Let s see an example of the law of conservation of mass and its meaning. If 2 g of hydrogen react exactly with 16 g of oxygen and they produce water, the mass of water that is going to be obtained is exactly 18 g (2+16). The law of conservation of mass is something that might be obvious nowadays but it was not obvious at Lavoisier s time, the XVIII th century. Lavoisier measured the mass of the reagents in several reactions and checked that it was the same mass as the mass of the products that was obtained after the reactions. If gases were involved, Lavoisier had to make sure they couldn t escape from the container of the chemical reaction, so he could measure their mass too. In his experiments, Lavoisier obtained that the mass of the reagents was always equal to the mass of the products, so he could state the law that carries his name. A political and social liberal, Lavoisier took an active part in the events leading to the French Revolution, and in its early years he drew up plans and reports advocating many reforms, including the establishment of the metric system of weights and measures. Despite his eminence and his services to science and France, he came under attack as a former farmer-general of taxes and was guillotined in a) Why do you think Lavoisier is considered the father of chemistry? b) Why was experimentation so important to obtain the law of conservation of mass? c) After Lavoisier was killed, a noted mathematician, Joseph-Louis Lagrange, remarked, It took them only an instant to cut off that head, and a hundred years may not be enough to produce another like it. What do you think he meant?

4 Exam of units 0 (inorganic nomenclature) and 1 (scientific activity) of 3º ESO B (answers) Name.... Exercise 1 Formulate or name: 1. fluorine (difluorine) F 2 2. H 2 Se dihydrogen selenide (hydroselenic acid) 3. manganese trihydroxide Mn(OH) 3 4. TeO stoichiometric: tellurium monoxide; stock: tellurium (II) oxide 5. Pentaoxygen dibromide O 5 Br 2 6. CaCl 2 stoichiometric: calcium dichloride; stock: calcium chloride 7. Iron (III) iodide (iron triiodide) FeI 3 8. Ag 2 O 2 stoichiometric: disilver dioxide; stock: silver peroxide 9. Sodium carbonate Na 2 CO Chromium (II) hydride (chromium dihydride) CrH 2 Exercise 2 a) Hypothesis (definition). False hypothesis and true hypothesis. Page 11. b) Experimentation. Explain. Page 12. Why, when studying how a variable affects the results of an experiment, all the other variables must remain constant? Because we don t want the other variables to affect the experiment, so that we know that any change in the results are caused by the change in the variable we are studying. Exercise 3 Steps of the scientific method. Brief definition of each one. Pages Exercise 4 Explain the experiment we did in the laboratory last week (the pendulum and its period). Explain the different variables we studied and if these variables affect the period of the pendulum or not. Pages 8 and 9. The mass and the angle don t affect the period. The length affects the period. Due to lack of time, the data that you obtained in the laboratory probably has a lot of errors. If you had more time to do this experiment, what would you do to minimize the errors of the measurements? Repeat each measurement several times (the more the better). The value of the period will be the average of the measurements. Exercise 5 Change the following units using conversion factors. Express the final result in scientific notation rounding off to two decimals dg/cm 3 to hg/m dam/min to mm/s g to g ps to ns dm 3 /h to ml/s (Remember 1 ml=1 cm 3 ) kg m/s to g cm/h

5 Exercise 6 A car is stopped at a red traffic light. When it turns green, it starts moving and we can measure the space it travels after some seconds: time (s) space (m) Represent the data. 2. Write its mathematical function. 3. What is the space the car has travelled after 3 seconds? 4. What is the time the car needs to travel 100 m?

6 Exercise 7 Antoine-Laurent Lavoisier, a meticulous experimenter, revolutionized chemistry. He established, among other things, the law of conservation of mass. He experimented with many chemical reactions (in chemical reactions some substances, the reagents, are transformed into different substances, the products) and proved that in a chemical reaction mass is neither created nor destroyed, it is only transformed. Therefore, the mass of the reagents is always equal to the mass of the products that are obtained. Let s see an example of the law of conservation of mass and its meaning. If 2 g of hydrogen react exactly with 16 g of oxygen and they produce water, the mass of water that is going to be obtained is exactly 18 g (2+16). The law of conservation of mass is something that might be obvious nowadays but it was not obvious at Lavoisier s time, the XVIII th century. Lavoisier measured the mass of the reagents in several reactions and checked that it was the same mass as the mass of the products that was obtained after the reactions. If gases were involved, Lavoisier had to make sure they couldn t escape from the container of the chemical reaction, so he could measure their mass too. In his experiments, Lavoisier obtained that the mass of the reagents was always equal to the mass of the products, so he could state the law that carries his name. A political and social liberal, Lavoisier took an active part in the events leading to the French Revolution, and in its early years he drew up plans and reports advocating many reforms, including the establishment of the metric system of weights and measures. Despite his eminence and his services to science and France, he came under attack as a former farmer-general of taxes and was guillotined in a) Why do you think Lavoisier is considered the father of chemistry? Because of his many experiments in chemistry. Some of them lead him to establish the law of conservation of mass. b) Why was experimentation so important to obtain the law of conservation of mass? Because in all the chemical reactions Lavoisier studied, the law of conservation of mass was always satisfied. That s how he could prove this law. c) After Lavoisier was killed, a noted mathematician, Joseph-Louis Lagrange, remarked, It took them only an instant to cut off that head, and a hundred years may not be enough to produce another like it. What do you think he meant? Lavoisier achieved so many things in chemistry that by killing him humanity lost a great scientist. In order for humanity to have a scientist as great as Lavoisier, Lavoisier s contemporaries might have to wait a long time.

Chemical Reactions: The Law of Conservation of Mass

Chemical Reactions: The Law of Conservation of Mass What happens in a Chemical Reaction? Chemical bonds in the reactants are broken, then atoms are rearranged to form new substances (products). Reactants