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Question:  1g of copper powder was taken in a  China dish and heated. What change  takes place on heating? When hydrogen  gas is passed over this heated substance,  a visible change is seen in it. Given the  chemical equations of reactions, the  name and the colour of the products  formed in each case.  [CBSE Delhi, Set 1, 2020] Answer:  When the copper powder is heated in a  China dish, the copper powder surface  becomes coated with black colour  substance due to the formation of copper  oxide by surface oxidation. Copper reacts  with oxygen in the air upon heating and  forms copper oxide. The black colour is  due to the formation of this copper oxide.  2Cu(s) + O ₂ (g) → 2CuO When hydrogen gas is passed over hot  copper oxide, the black coating on the  surface turns brown as the reverse reaction  takes place and copper is obtained. CuO + H ₂  → Cu + H ₂ O

Question:  Identify the type of each of the following  reactions. Also write balanced chemical  equation for each reaction. (i) A reaction in which the reaction  mixture becomes warm. (ii) A reaction in which an insoluble  substance is formed.  [CBSE, OD, Set 3, 2020] Answer:  (i) Reactions in which the reaction mixture  becomes warm and heat is released  along with the formation of products  are called exothermic reactions.  Example of exothermic reactions:  Burning of natural gas CH ₄ (g) + 2O ₂ (g) → CO ₂ (g) + 2H ₂ O(g) CaO + H ₂ O → Ca(OH) ₂ (ii) Reactions in which an insoluble  substance is formed is known as  precipitation reaction. For example:  Solutions of barium chloride and  sodium sulphate in water react to  give insoluble barium sulphate and  the solution of sodium chloride. Na ₂ SO ₄ (aq) + BaCl ₂ (aq) → BaSO ₄ (s)  + 2NaCl(aq)

Question:  Mention with reason the colour changes  observed when: (i) silver chloride is exposed to sunlight. (ii) copper powder is strongly heated in  the presence of oxygen. (iii) a piece of zinc is dropped in copper  sulphate solution.  [CBSE, OD, Set 1, 2020] Answer:  (i) When silver chloride (white) is exposed to sunlight, it undergoes photochemical decomposition forming  black metallic coloured silver and  greenish yellow gas chlorine. Thus,  the change in colour is observed due  to the oxidation of silver chloride in  the presence of sunlight. (ii) Heated copper metal reacts with  oxygen to form the black copper  oxide. Thus, the change in colour is  observed when copper powder is  strongly heated.  2Cu (s) + O₂ (g) → 2CuO (s) (iii) On adding zinc to CuSO₄ solution,  zinc displaces copper from copper  sulphate and forms zinc sulphate  solution. This is indicated by colour  change from blue to colourless.  CuSO4 solution has a blue colour  while ZnSO4 solution is colourless.  Zn(

Question:  While studying the double displacement  reaction, the solutions of barium  chloride and sodium sulphate are mixed  together. (i) What do you observe as soon as the  two solutions are mixed together? (ii) What will happen in the above  observation made by you after ten  minutes?  [CBSE, Term 1, Set 1, 2015] Answer:  (i) The reaction mixture becomes white  in colour as a precipitate of BaSO4 i.e.  Barium sulphate is formed. (ii) White precipitate settles down after  10 minutes.

Question:  Rahul has been collecting copper  coins and silver coins. One day he  observed a green coating on copper  coins and a black coating on silver  coins. State the chemical phenomenon  responsible for these coating and also  write chemical names of each coating.  [CBSE, Term 1, Set 1, 2016] Answer:  The chemical phenomenon responsible  for the coatings is corrosion. Copper and  silver metals in presence of moist air  gets oxidised forming protective layer  over them. Silver turns black due to the  formation of silver sulphide (Ag ₂ S) while  copper turns green due to the formation  of a mixture of copper carbonate and  copper hydroxide [CuCO₃⋅Cu(OH)₂].

Question:  A student added few pieces of  aluminium metal to two test tubes A  and B containing aqueous solution of  iron sulphate and copper sulphate. In  the second part of her experiment, she  added iron metal to another test tube  C and D containing aqueous solution  of aluminium sulphate and copper  sulphate.   In which test tube or test tubes will she  observe colour change? On the basis of  this experiment state which one is the  most reactive metal and why?  [CBSE, 2018] Answer:  Only in test tubes A, B and D she will  observe colour change from green to  colourless in A because aluminium is  more reactive than iron, it will displace  iron. She will observe colour change from  green to colourless in test tube B. She will  also observe colour change in test tube D  from blue to light green. Aluminium is the  most reactive metal because it displaces all  the other three metals.

Question:  What is observed when a solution of  sodium sulphate is added to a solution  of barium chloride in a test tube? Write  equation for the chemical reaction  involved and name the type of reaction  in this case. [CBSE, 2018] Answer:  Na₂SO₄ (aq.) + BaCl₂(aq.) → BaSO₄↓(s) + 2NaCl(aq.)  Sodium Barium Barium Sodium  sulphate chloride sulphate chloride  It is an example of double displacement  reaction.

Question:  What would a student report nearly after  30 minutes of placing duly cleaned strips  of aluminium, copper, iron and zinc in  freshly prepared iron sulphate solution  taken in four beakers?  [CBSE OD, Set 1, 2019] Answer:  Aluminium displaces the iron from iron  sulphate and the colour of two solution  changes from green to colourless.  No change takes place when copper strip  is dipped in iron sulphate solution.  No change will be observed when iron  strips are dipped in iron sulphate solution.  The colour of the solution changes from  green to colourless when zinc is added to  iron sulphate solution.

Question:  In the experimental set up to show that  ’’CO ₂  is given out during respiration’’,  name the substance taken in the small  test tube kept in the conical flask. State  its function and the consequence of  its use. [CBSE Delhi, Set 1, 2019] Answer:  The chemical kept in the test tube is  KOH–Potassium hydroxide. The function  of this chemical is to absorb the vapours  of CO ₂ .  Consequences: The water level rises in the  test tube dipped.

Question:  Which of the following solution is  coloured? (a) ZnSO₄  (b) FeSO₄ (c) Al₂(SO₄)₃  (d) Na₂SO₄  [CBSE, Term 1, Set 1, 2015] Answer:  (b) FeSO ₂

Question:  Aqueous solution of which of the  following is colourless? (a) FeSO₄  (b) ZnSO₄ (c) Al2(SO₄)₃  (d) Both (b) and (c)  [CBSE, Term 1, Set 1, 2015] Answer:  (d) Both (b) and (c)

Question:  In a double displacement reaction  such as the reaction between sodium  sulphate solution and barium chloride  solution:  [CBSE Delhi, Set 1, 2020] (A) exchange of atoms takes place (B) exchange of ions takes place (C) a precipitate is produced (D) an insoluble salt is produced The correct option is: (a) (B) and (D)  (b) (A) and (C) (c) only (B)  (d) (B), (C) and (D) Answer:  (d) (B), (C) and (D)

Question:  When hydrogen sulphide gas is passed  through a blue solution of copper  sulphate, a black precipitate of copper  sulphide is obtained and the sulphuric  acid so formed remains in the solution.  The reaction is an example of a:  [CBSE Delhi, Set 1, 2020] (a) Combination reaction (b) Displacement reaction (c) Decomposition reaction (d) Double displacement reaction Answer:  (a) Combination reaction

Question:  Calcium oxide reacts vigorously with  water to produce slaked lime.  CaO(s) + H₂O(l) → Ca(OH)₂(aq)  This reaction can be classified as: (A) Combination reaction (B) Exothermic reaction (C) Endothermic reaction (D) Oxidation reaction  [CBSE Delhi, Set 1, 2020] Which of the following is a correct  option? (a) (A) and (C) (b) (C) and (D) (c) (A), (C) and (D) (d) (A) and (B) Answer:  (d) (A) and (B)

Question:  In which of the following, the identity of  initial substance remains unchanged? (a) Curdling of milk (b) Formation of crystals by process of  crystallisation (c) Fermentation of grapes (d) Digestion of food  [CBSE OD, Set 1, 2020] Answer:  (b) Formation of crystals by process of  crystallisation.

Question:  What was the nationalist message of Swadeshi regarding advertisements? Answer:  The Swadeshi movement gave the message to boycott the foreign made  cotton and other clothes as this made India dependent and thus people would never be  developed neither will there be any development of the country in terms of industrial  production. This movement asked the government to increase the tariff of foreign goods  for the protection of the domestic economy.  The companies protested for their collective interest and asked the government to give  the producers other concessions.

Question:  Who were gomasthas? Answer:  The East India company of textiles appointed paid labour servants who were  responsible for supervising weavers, collecting the supplies and examining the quality of  cloth they were called “GOMASTHAS”.  A Gomastha of the eighteenth century, painting on wood.

Question:  Which product in India dominated the international market before the age of  machine industries? Answer:  Before the age of machine industries, silk and cotton were the goods that had  dominated all the markets of the international arena. The cotton and textiles produced in  other countries were coarse, and the one produced in India was very fine in quality, and  thus the countries in the fertile crescent and the south Asian countries like Persia, Saudi  Arabia and Germany traded goods from India across the seaports.

Question:  Who were the competitors of the East India Company in the textile industry  in the eighteenth century? Answer:  In the eighteenth century, it was not only the Indian subcontinent that was  producing cotton, but other countries were also giving their best.  The East India Company was going well until in the eighteenth century the European  country companies became their competitors. These European companies took the  concessions on various reasons and taxes and took the monopoly right of trade among  various places of the globe where textiles were high in demand. The Portuguese,  French and Dutch came in the market as the major competitors for woven cloth. This  affected the East India company textile production on a large scale.

Question:  Why was the demand of labours seasonal? Answer:  The seasonal demand for labour means that the labour that is required by the  industries is depended on the season that is present there. Mostly the labour is required  during a particular season in a very large number, and as the season , passes, the  labour requirement becomes zero. In many industries, the work was seasonal, so the  employers demand for labourers was seasonal. This can be explained as follows: Many  industries had worked only during certain months and seasons of the year. The gas  work industries were also busy during the winter months. 1. The demand for certain labour was seasonal like, breweries, where beer was made  was busy during winter seasons. 2. Bookbinders and printers catered to the festive season of Christmas. Winter was also  the month where ships were taken for cleaning.  All these industries needed extra labour during their time of the year and thus in the rest  of the month's labour was wi

Question:  Who Created the cotton mill? Answer:  A cotton mill is a machinery that is usually set up inside the building. It does  the work of weaving and spinning and produces cotton yarn or basically cotton cloth.  This machine was created in 1771. The cotton mill was created by Richard Arkwright.

Question:  Who manufactured a new model of the steam engine? Answer:  A steam engine is a machine that does mechanical work by using heat as its  the main ingredient. The new model of the steam engine was made by James Watt and  Mathew Boulton. They both worked hard and opened a mill that was called the Boulton  and Watt in Birmingham, England in the 18th century.

Question:  How did a wave of economic nationalism strengthen the wider nationalist  sentiment growing in Europe? Explain. Answer:  The wave of economic nationalism strengthen the wider nationalist sentiment  growing in Europe due to the Following Reason:- 1. The movement of liberalism started with the goal to achieve freedom of markets and to  abolish restrictions imposed on the movement of goods and capital. 2. Napoleon introduced such administrative measures which created countless  principalities. All these small principalities had their own system of currency, weights,  and measures. So if the merchants had to travel across, he had to cross around 11  customs barriers and pay customs duty on each item which was 5% per item. This  problem created a wave of Economic Nationalism. 3. Duties on the goods were imposed on the basis of weights and measures. Also,  different regions had their own system of weights and measures which were often time consuming task. 4. New Commercial classes

Question:  ‘The development of nationalism did not come about only through wars  and territorial expansion.’ Answer:  ‘The development of nationalism did not come about only through wars and  territorial expansion’, it was said so because – wars and territorial expansion were not  the only two reason behind the development of nationalism, but there were many other  reasons which were:- 1. Art and poetry, stories and music which are the part of Culture and traditions also  played a significant role in the development of nationalist sentiments. 2. The concept of Romanticism developed during that time gave rise to the group of  romantic artists who started expressing emotions, intuitions, and mystical feelings  through their art. They criticised reason and science. Example – Johann Gottfried  Herder, German Philosopher, believed that German culture should be introduced  among the common people, which should be possible only through folk songs, poetry,  and dances. So, the collection of su

Question:  Who was Count Camillo de Cavour? Mention his contributions. Answer:  Count Camillo de Cavour also known as Cavour, was the Chief Minister of  Italy. He was not a democrat or a revolutionary but an Italian statesman who actively  participated in Italian unification. He spoke French better than Italian. His contributions  were: 1. He was one of the individuals who fought for the unification of Italy. He took the  initiative to unify the regions of Italy by inspiring people through his ideas. 2. He introduced several economic reforms in his native place in Piedmont and  Risorgimento was the political newspaper started by him. 3. In 1859, Sardinia Piedmont successfully defeated the Austrian forces. This was  possible because Count Camillo de Cavour formed the diplomatic alliance. 4. With his diplomacy, he successfully made Piedmont a new great power in Europe. 5. He practiced such policies which were adopted during post-Italy unification.

Question:  Explain how did the 18th and 19th-century artist begin personifying a  nation in allegory. Answer:  Artists in France found a way out by personifying a nation. In the 18th and  19th century artists begin personifying a nation in an allegory. Allegory is to reveal the  hidden meaning of something or giving a form to formless. It means artists personified  nation as a female figure not as a woman of real life but as a figure with physical  existence and in concrete form. Also, Germania, the female figure personified as the  German nation. In this figure, she wears the crown of oak leaves, and German oak  Leaves stands for Heroism. There is one more image where Germania is standing with  the sword for protecting the Rhine River.  During the French revolution, artists created allegory by personifying a female figure as  a symbolism of Liberty, Justice, and Republic. Specific objects and symbols were used  to personify this. Like this only, in the 19th century, a popular Christia

Question:  The Balkan issue became one of the major factors responsible for the First  World War. Explain by giving examples. Answer:  The Balkan was a region with diversity, ethnicity and geographical variation,  which comprises of following countries – modern-day Romania, Bulgaria, Greece,  Albania, Macedonia, Croatia, Bosnia- Herzegovina, Slovenia, Serbia, and Montenegro.  Its inhabitants were known as Slavs. The Balkan issue become one of the major factors  responsible for the First World War. Some of the examples were – 1. Many parts of the Balkan were under the control of the Ottoman Empire. The idea of  romantic nationalism and the disintegration of the Ottoman Empire intensified the  situation, even though Ottoman empire tried to strengthen its position by introducing  reforms but didn’t succeed, so the Balkan people demanded independence and political  rights. They also proved that they were always free but later subjugated by foreign  powers. 2. In Balkan, Slavic Nationalitie

Question:  Describe any four features of the Vienna Treaty of 1815 in Brief. Answer:  The treaty of Vienna of 1815 stated that all the changes that had come due to  the Napoleonic war should be reversed. The four features of the Vienna treaty of 1815  were:- 1. The Bourbon dynasty which was removed forcefully was brought back into power.  Under Napoleon whichever the territories was acquired by France was lost again. 2. On the boundaries of France, series of states established which prevented expansion  of France, such as in the North-kingdom of Netherlands was set up; in the South Genoa  was set up; on its western frontier - new territories and a portion of Saxony was given to  the Prussia; the control of Northern Italy was given to Austria, and the part of Poland  was given to Russia in the east. 3. Napoleon established German confederation of 39 states which remained an  untouched subject. 4. The main feature of the treaty of Vienna was to re-establish all the monarchies thrown  out

Question:  Otto von Bismarck was the architect of ‘German unification.’ Explain. Answer:  Yes, it is true that Otto von Bismarck was considered as the architect of  ‘German unification.’ Otto von Bismarck, who along with Prussian army and  bureaucracy completed the process of German Unification. Following were the reason  which proves that Otto Von Bismarck contributed significantly to German Unification and  became its architect – 1. The middle-class population of Germany decided to unite the different regions of  German Confederation into a nation with an elected parliament. The group of the large  landowners called Junkers of Prussia supported the combined forces of military and  monarchy. In this process, Prussia participated and took up the leadership and Otto von  Bismarck became its Chief Minister. 2. He carried out this process of national unification with Prussian army. 3. In this process, three wars took place with Austria, Denmark, and France. Prussia won  and eventually the

Question:  Like Germany, Italy too had a long history of political fragmentation.  Justify. Answer:  Yes, it is true that Italy had a long history of political fragmentation. It is said so  because – 1. The population of Italy was divided according to several dynasties and Multi-national  Habsburg Empire. Italy was divided into seven states – like Sardinia- Piedmont was the  only region ruled by Italian princely house, Pope ruled the Centre, North was ruled by  Austria Habsburgs and southern regions was ruled by Bourbon Kings of Spain. 2. There was not one Italian language or a common Italian language instead it had many  regional and local variations which show that Italy was not unified in terms of culture.  All this shows that Italy like Germany was politically fragmented and was unstable.

Question: Describe any three consequence of liberal revolution of 1848. Answer: The three consequence of liberal revolution of 1848 were: In February 1848, Republic was formed which provided suffrage, i.e., the right to vote in political elections to all the male adults above 21 and promised right to work. Accordingly, national workshops were set up to provide employment opportunities. It also brought the refusal or rejection of the monarchical power in France in 1848. Liberal middle-class population including men and women demanded Constitutionalism with the goal of national unification. Overall, the idea to create a nation states based on 3 principles were - a Constitution, Freedom of the press and Freedom of association.