Assignment Class 10

ASSIGNMENT NO 1 ON CHEMICAL REACTIONS AND EQUATION

1-mark Questions/ Answers

1. What happens when magnesium ribbon burns in air?

Ans. When magnesium ribbon burns in air, it combines with the oxygen to form magnesium oxide.

 2Mg(s) + O2(g) ® 2MgO(s)

2. Name the gas evolved when zinc reacts with dil. HCl.

Ans. Hydrogen gas is evolved.

3. What is a chemical equation?

Ans. A chemical equation is a symbolic notation that uses formulae instead of words to represent a chemical equation.

4. On what chemical law, balancing of chemical equation is based?

Ans. Balancing of a chemical equation is based on the law of conservation of mass.

5. Represent decomposition of ferrous sulphate with the help of balanced chemical equation.

Ans. 2FeSO4(s) ® Fe2O3(s) + SO2(g) + SO3(g)

6. When carbon dioxide is passed through lime water, it turns milky, why?

Ans. Lime water (calcium hydroxide) combines with carbon dioxide to form a suspension of calcium carbonate which makes lime water milky. Ca(OH)2 + CO2 ® CaCO3 + H2O

7. A zinc rod is left for nearly 20 minutes in a copper sulphate solution. What change would you observe in zinc rod?               

Ans. Zinc rod will change into zinc sulphate.

8. What type of reaction is this:  Na2SO4           +          BaCl2   ®         BaSO4 +          2NaCl

Ans. It is a double displacement reaction.

9. Identify the compound oxidized in the following reaction. H2S (g) + Cl2  ®  S(s) + 2HCl (g)

Ans. H₂S is oxidized.

10. What is rust? Ans. Rust is mainly hydrated iron (III) oxide, Fe2O3.xH2O.

11. How does the food become rancid?

Ans. Food becomes rancid when fat and oils present in the food are oxidized.

2-marks Questions/ Answers

Q.1. An iron knife kept dipped in a blue copper sulphate solution turns the blue solution light green. Why?

Ans. As we know iron is more reactive than copper. So, it displaces Cu from CuSO4 solution and forms ferrous sulphate which is of Light Green Colour.

CuSO4 (aq) + Fe (s)      →        FeSO4(aq)                  +               Cu(s)

 Blue colour                            light green colour

Q.2. A copper coin is kept in a solution of silver nitrate for some time. What will happen to the coin and the colour of the solution?

Ans. We know that copper is more reactive than silver, so it will displace silver from its salt solution:

 Cu(s)   +          2AgNO3(aq)      →        Cu(NO3)2(aq)    +          2Ag(s)

So the solution will turn blue due to the formation of copper nitrate.

Q.3. What do you understand by precipitation reaction? Explain with suitable examples.

Ans.  Precipitate. When two reactants react and product formed remains insoluble and settles as a solid it is called a precipitate. Such reactions in which precipitate is formed are called precipitation reactions. For example,(i) when aqueous solution of sodium sulphate is mixed with the aqueous solution or barium chloride, barium sulphate comes in the form of white precipitate

Na2SO4(aq)      +          BaCl2(aq)          →        BaSO4(↓)          +          2NaCl(aq)

 (ii) When aqueous solution of sodium chloride is mixed with the aqueous solution of silver nitrate, silver chloride comes in the form of white precipitate.

Q.4. What is lime-water test for the detection of carbon dioxide?

Ans. When carbon dioxide gas is passed through lime water ,it turns milky due to the formation of milky suspension (precipitate) of calcium carbonate. Carbon dioxide is produced by the action of dilute HCl on sodium carbonate.

Na2CO3(s)        +          2HCl(aq)           →         2NaCl   +          H2O(l)   +          CO2

Carbon dioxide gas produced in this reaction is passed through lime water that changes to milky colour due to the formation of calcium carbonate.

 Ca(OH)2(aq)     +          CO2(g)              →         Caco3   +          CO2(g)

3 Marks Questions/ Answers

Q.5. What is corrosion? State the conditions necessary for rusting of iron. How rusting is harmful?

Ans:  Corrosion. The process of eating away of the metal by the action of atmospheric reagents changing the metal into its compound is called corrosion.

Rusting of Iron. When iron and iron objects are exposed to atmosphere, they are attacked by air and moisture (water) of the atmosphere and a brown and orange coloured layer is formed on the surface. It is called rust which is mainly hydrated iron (iii) oxide Fe2O3.xH2O.

Harmful Effect of Rusting. Hydrated iron (iii) oxide is brittle substance and moves away from the surface thus the object is damaged. The objects get holes, cavities and rough surface.

Conditions necessary for rusting :

(i) Open surfaces of the metal.   (ii) Presence of air (Oxygen).  (iii) Presence of moisture (water).

Q.6. What is rancidity? Write the common method to prevent it.

Ans. When food item are kept unprotected for some time, they give some unpleasant smell and taste and become rancid. This process is called rancidity. Actually, the micro organisms oxidise the fat and oils present in them. So oxidation of food items need to be prevented to protect them.

Common methods to Prevent Rancidity of Food item:

(i) Keeping the food at low temperature             (ii) Keeping food item in air tight containers

(iii) By filling nitrogen in the food storage bags.

5 Marks Questions/ Answers

1. a. Why cannot a chemical change be normally reversed?

b. why is it always essential to balance a chemical equation?

c. what happens when CO2 gas is passed through lime water and why does it disappear on passing excess CO2?

d. Can rusting of iron takes place in distilled water?

Ans:  a. In a chemical change some bonds are broken and some bonds are formed. The products are quite different from the reactants. Therefore it normally can’t be reversed.

b. A chemical equation has to be balanced to satisfy the law of conservation of mass.

c. On passing CO2 gas through lime water, it turns milky due to formation of insoluble calcium carbonate which dissolves on passing excess CO2 due to formation of soluble calcium bicarbonate.

Ca(OH)2 + CO2(g) --------------→ CaCO3(s) + H2O(l)

CaCO3(s) + H2O(l) + CO2 (g) ---------------→ Ca(HCO3)2(soluble)

d.  No, rusting of iron cannot take place in distilled water because it neither contains dissolved oxygen nor CO2 both are essential for rusting of iron.

Hots Questions

Q 1 . The marble statues often slowly get corroded when kept in open for a long time .Assign a suitable explanation

Ans-SO2,NO2 gases are released into the atmosphere from various sources. These dissolve in rain water to give acid which corrodes marble statues

2SO2+O2 --------------→ 2SO3                      

H2O+SO3 --------------→ H2SO4

2NO2+H2O 2HNO3 CaCO3+H2SO4--------------→ CaSO 4 +H2O+CO2

CaCO3+2HNO3 --------------→Ca(NO3)2+H2O+CO2

 Q 2. You are given the following materials

 (1) marble chips (2)dilute hydrochloric acid (3)Zinc granules ,identify the type of reaction when marble chips and Zinc granules are added separately to acid taken in two test tubes

Ans-(i) marble chips react with dilute hydrochloric acid to form calcium chloride and carbon dioxide .it is a double displacement reaction

CaCO3+2HCl → CaCl2 + H2O +CO2

(ii)Zinc granules react with dilute hydrochloric acid to give hydrogen gas. it is a displacement reaction

Zn(s)+2HCl → ZnCl2(aq)+H2(g)

Q3. The gases hydrogen & chlorine do not react with each other even if kept together for a long time . However , in the presence of sunlight , they readily combine . What does actually happen ?

Ans-In Chemical reactions , energy is needed to break the bonds present in the reacting molecules so that they may combine to form the products . In this reaction , sunlight is the source of energy in the form of photons . The energy made available by sunlight helps in breaking the bonds & this leads to chemical reaction between hydrogen & chlorine.

 H2 (g) + Cl₂(g) sunlight→ 2HCl (g)

Q 4. A,B&C are three elements which undergo chemical reactions in the following way

A2O3 + 2B®B2O3 + 2A                   3CSO4 + 2B -® B2(SO4)3 + 3C                   3CO+ 2A ®A2O3 +3C

Answer the following

(A) Which element is most reactive ?        (B) Which element is least reactive ?

Ans:  a) The most reactive element is ‘B’. It has displaced both ‘A’ and ‘c’ from their compounds.

b) The least reactive element is ‘C’ as it has been displaced by both ‘A’ and ‘B’ .

Q. A water insoluble substance ‗X‘ on reacting with dilute H2SO4 released a colourless and odourless gas accompanied by brisk effervescence. When the gas was passed through water , the solution obtained turn blue litmus red . On bubbling the gas through lime water , it initially became milky and the milkiness disappeared when the gas was passed in excess . Identify the substance ‗X‘ and write the chemical equations of the reaction involved

ANS: the water insoluble substance ‘X’ is most probably metal carbonate ( CaCO3 ). The chemical reaction that involved are given below

CaCO3 (s) + H2SO4 (aq) →CaSO4 ( aq) + H2O (aq) + CO2 (g)

Ca(OH)2 (s) + CO2 (g) → CaCO3 (s) ( milky)  + H2O (l)                                          

 CaCO3 (s) + CO2 (g) + H2O (aq) →Ca(HCO3)2     ( milkiness)

Extra score questions:

Q 1. If you collect  silver coins and copper coins. After some day a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings

Ans: Corrosion is responsible for this coating. Black coating is due to formation of Ag₂S and green coating is due to formation of CuCO₃.Cu (OH)₂

Q.2. An aqueous solution of metal nitrate P reacts with sodium bromide solution to form yellow ppt of compound Q which is used in photography. Q on exposure to sunlight undergoes decomposition reaction to form metal present in P along with reddish brown gas. Identify P&Q . Write the chemical reaction & type of chemical reaction.

Ans: P = Ag NO3 , Q = AgBr                             2 A gBr (s) ® 2Ag(s) + B r₂(g) Photochemical decomposition

Q.3. A substance X used for coating iron articles is added to a blue solution of a reddish brown metal Y, the color of the solution gets discharged Identify X and Y & also the type of reaction.

Ans. 6 X= Fe, Y = Cu, Displacement reaction.

Q.4. A student burnt a metal A found in the form of ribbon. The ribbon burnt with a dazzling flame & a white powder B is formed which is basic in nature. Identify A &B. Write the balanced chemical equation.

Ans.11 X = Mg, Y = MgO,                               Mg + O2® 2 MgO

Q.5.  why magnesium ribbon cleaned before burning?

Ans: The magnesium ribbon is always found with a white layer of MgO  due attack of moist air. So, magnesium ribbon cleaned before burning.

Q.6.  During electrolysis of water gas collected in one test tube is double than other why?

Ans: On electrolysis weter decompose into hydrogen and oxygen in ratio  2:1 by volume so,H₂ gas collected in one test tube is double than O₂

CHAPTER 16 . MANAGEMENT OF NATURAL RESOURCES 

Q1)Name a bacteria found in human intestine?

Ans-coliform bacteria is found in human intestine.

Q2)Which is the easiest method to detect water pollution?

Ans-pH detection using the universal indicator.

Q3)A person lives near a forest.Enlist 4 items which he can get from forests to meet his daily needs.

Ans-food, fodder,fuel and medicinal plants.

Q4)Why are forest called “biodiversity hot spot”?

Ans-forest are rich in most of the species of flora and fauna.All species of plants like bryophyte,pteridophyta,ferns, gymnosperms,angiosperms and animal species from amoeba to man are found.

Q5)Name 4 substances that can be recycled.

Ans-glass,plastics,metals and paper.

Q6)What do you mean by the trm sustainable development?

Ans-Sustainable development means to meet the needs of present generation ,without foreclosing the options of future generation,to keep balance between development and environment.

Q7)How does mining lead to pollution?

Ans-mining causes pollution because the large amount of slag is discarded for every tonne of metal extracted in the earth.

Q8)”Coal and petroleum are converted forms of solar energy”.is this statement correct?

Ans-this is statement is correct because millions of years ago the raw material from which coal and petroleum are derived were daed and decayed plants , which when were living photosynthesized by solar energy.

Q9)Hydroelectric power is also an indirect form of solar energy.how?

Ans-hydroelectric power is indirect form of energy, because the water which is stored in dams is rainwater and rainfall occurs due to evaporation of water from water bodies due to heat of the sun.

Q10)Writeatleast two ways by which people of ancient India managed water resources?

Ans-a)kulhs in Himachal Pradesh (b)khadins in rajasthan.

Q11)What will happen if loss of biodiversity occurs?

Ans-when loss of biodiversity will occur ,it will lead to ecological crisis, the foodcahins and food webs will get disturbed and resources will not be available for future generations.

Q12)What strategies should be adopted such that forest products are used and the environment also does not get disturbed?

Ans- a)reforestation and afforestation to remake forests.
        b)not allowing monoculture of plants.
       c)employment of local people for maintenance of forests .
       d)killing of animals should be banned.Steps to create awareness among people to save the            
       endangered flora and fauna should be taken.

Q13)Besides conservation of wildlife and forest , suggest some ways which can improve our environment.

Ans - a)water conservation , mainly fresh water.
         b)use of coal and petroleum should be done judiciously as its sources are limited.
        c)recyclable material such as paper, glass ,metals should be segregated from the                  
         trash.Biodegradable trash should be used for bioenergy through fermentation and anaerobic      
         respiration to produce biogas.
         d)oxides of sulphur and nitrogen should not be released into the atmosphere.
Q14)What is watershed management?what is its aim and what are the benefits?

Ans-watershed management is a scientific way of developing primary and secondary sources of water .Its main aim is to develop primary sources of land and water and use scientific methods to increase the biomass production as secondary sources so that no ecological imbalance occurs.They work on rejuvenating ancient and traditional way of water storage along with mega- projects like dams and reservoir

Q15)what you can do as an individual to reduce consumption of various nature resoources and help in environment conservation?

Ans a)follow 3 R’s(reduce,recycle, and reuse)
        b)wastage of paper and water can be reduced .
        c)extra food should be given to poor instead of throwing it.
        d)plastic, polythene, metal cans can be recycled.e)wastage of electricity, petrol, diesel, LPG can be  
        prevented.

Type-II CHAPTER 16 . MANAGEMENT OF NATURAL RESOURCES.1 MARKS QUESTIONS

1. What will be the effect of increase in the amount of CO2 in the atmosphere on the average temperature of the earth. 

Ans. The average temperature of the earth will increase.

2. Why is it necessary to conserve our environment?

Ans Conservation of environment is required for preventing damage to environment and depletion of natural resources

3. Which of the following is the major constituents of biogas. CO2, H2, CH4, CO.

Ans.CH4

4.Which of the following pollutants of air would affect the capacity of blood in human bodies to absorb O2 from lungs . NO2 SO4,CO,CO2

Ans.CO

5. Where was CHIPKO MOVEMENT started?

Ans: Reni in Garhwal.

6. What will be the result of presence of excess amount of CO2 in environment.

Ans.Green house effect.

7.What are the two major benefits of dams?

Ans. 1. Irrigation 2. To produce electricity.

8.What are kulhs?

Ans.Kulhs are age old concepts of water harvesting used in Himachal Pradesh.

9.List any two systems of water harvesting.

Ans Ponds and check dams

10 How is the increase in demand for energy affecting atmosphere?

Ans. Increased consumption of fossil fuels is releasing a lot of polluting gases some of which are causing Global Warming and producing acid rain

2 MARKS QUESTIONS.

1.Write two advantages of classifying energy sources as renewable and non renewable.

Ans.
(a).A judicious use of non renewable energy source so as to prevent its depletion. 

(b) Increasing use of renewable energy source but not beyond its renew ability.

2. Why should we conserve forests? Suggest any two ways of conserving forests.

Ans.1.Forests provides us O2 which is required for living –Natural habitat, prevent soil erosion, and regulate water cycle.

2.They protect the soil, retain and regulate flow of rain water. 

Ans: Conservation of forests:

i.afforestation and reforestation 

ii.Social forestry.

3.What are fossil fuels. Give two examples of fossil fuels.

Ans .Fossil fuels are energy yielding combustible substances that have been formed millions of years ago by compression and anaerobic heating of organic matter. Ex coal and petroleum.

4.Write the ecological functions of forests.

Ans .Forests regulate climate they help in retaining rain water and its storage they control soil erosion and occurance of floods.

5.What is chipko movement? How did this movement ultimately benefit the local populations and the environment. 

Ans.It was a movement initiated by local people in Reni Village of Gharwal Region to oppose and protect trees in the forest.

6. How do the forests get depleted? What are its consequences?

Ans. Clearing forests for agriculture, roads canals, human habitation and building dams. Consequences: less rain fall, climatic change.

7 .Suggest any two measures for controlling Co2 levels in the atmosphere.

Ans. 1.Increased vegetation cover. 2. Using alternate sources of energy.

8 Why are Arabari forests of Bengal known to be good example of conserved forests.

Ans: Sal forests of south western districts of West Bengal regenerated with people participation.

Ans. Because villagers were involved in the protection of 1272 hectares of badly degraded sal forests. In return for help in protection villager,s were given employment in both silviculture and harvesting operations. 25% of final harvest was given to them and they were allowed fuel wood and fodder collection on nominal fee.

9.Why are environmentalists insisting upon sustainable natural resource management?Give any three reasons.

Ans. Equitable distribution, controlled exploitation, minimum wastage, disposal of waste.

10. Suggest any two ways of utilizing waste water.

Ans.

(i).Treated municipal water can be poured in irrigation channels for supply to crop fields.

2. Sewage sludge separated from waste water is a source of manure compost and bio gas

3 MARKS QUESTIONS.

1. Briefly describe Ganga action plan.

Hint. Details of steps taken to reduce pollution.

2. Explain the methods of water harvesting 

hint. check dams , khadins,kuhls etc of different states.

3. Quote three instances where human interventions saved the forests.

Hint.

1. Silent valley(Kerala) 2. Garwal Himalayas. 3. Kelase Forests.:

4. T here are four main stake holders when it comes to forests and wild life Which among these should be the authority to decide the management of forest produce? Why?

HINT people, forest department, industrialists, wild life and nature enthusiasts. People  living around the forest area

5. What is the importance of water harvesting.

Hint Importance in ground water recharging ,irrigation, drinking water supply

6. An environmentalist on your visit to your school suggested the use of three R‘s to save the environment.explain the three R‘s

Hint .Reduce Reuse Recycle.

7.What is meant by sustainable management? The environmentalists are insisting upon sustainable natural resources management?State four advantages.

Ans .It is controlling the use of resources in such a way so as to provide for its equitable and continuous availability not only to the present generation without any harmful impact on the environment.

Four advantages:

Equitable distribution, controlled exploitation,minimum wastage,disposal of waste

8 What is a dam? Write two main advantages and two illeffects of constructing a big dam

Ans. Dam is a large water reservoir built across a stream by holding back water during rainy seasons.

Advantages: prevention of floods, irrigation Ill effects.

1. Displacement of large people.

2. Ecological problems.

9. Why is replenishment of forests necessary?

Ans.

1. To maintain Ecological balance.

2. To prevent Soil erosion

3. To reduce the amount CO2 in atmosphere and check Global Warming.

4. To maintain rain fall.

5. They control occurrence of floods.

6. Provides habitat to animals.

10. List four changes you would incorporate in your life style in a move towards sustainable use of available resources.

Hint some changes in the life style

10th Carbon and Its Compounds 

Q.1 Why is carbon tetravalent? 
Ans 1: Carbon atom has 4 electrons in the outermost shell.It needs 4 more electrons to complete its 
octet. Therefore, carbon is tetravalent. 
Q.2 The formula of a hydrocarbon is Cn H2n. Name the family to which it belongs and also predict 
its nature. 
Ans 2: The hydrocarbon belongs to alkenes It is unsaturated in nature. 
Q.3 What is the valency of carbon in CH3-CH3, CH2=CH2 and HC=CH ? 
Ans 3: The valency of carbon in all its compounds whether saturated or unsaturated is 4. 
Q.4 Out of butter and ground nut oil , which is unsaturated in Nature? 
Ans 4: Groundnut oil is unsaturated in nature . 
Q.5 Why is high temperature not favourable for alcoholic fermentation? 
Ans 5: The high temperature destroys the enzymes which are needed to carry fermentation . 
Q.6 Name a cyclic unsaturated hydrocarbon, containing three double bonds? 
Ans 6: Benzene 
Q.7 What is the difference in the molecular mass of any two adjacent homologues? 
Ans 7 : 14 mass units.
Q.8 Which has triple bond ; C2H4 ,C3H6 and C3H4 ? 
Ans 8:C3H4 has triple bond in the formula .
Q.9 Which substance is added to denature ethyl alcohol? 
Ans 9: A small amount of methyl alcohol , pyridine or copper sulphate is added to denature ethyl alcohol . 
Q.10 Which ions are responsible for making water hard ? 10th Carbon and Its Compounds Solved Paper-1
File downloaded from: http://cbseadda.blogspot.com/ Page 2
Ans 10: Ca2+ and Mg2+ ions are responsible for making water hard. 
Q.11 Name the catalyst commonly used in hydrogenation of oil to form fats? 
Ans 11:Nickel. 
Q.12 Write the name and molecular formula of alcohol derived from butane ? 
Ans 12: C4H9OH Butanol 
Q.13 Which gas is evolved when sodium carbonate or bicarbonate is added to ethanoic acid ? 
Ans 13 : CO2 (carbon dioxide). 
Q.14 What is SCUM ? 
Ans 14: Scum is precipitate of Calcium and Magnesium salt of organic fatty acids. 
Q.15 What are hydrophobic and hydrophilic parts in soaps? 
Ans 15: The alkyl group(R) consisting of long chain of carbon atom is hydrophobic part while COONa 
group is hydrophilic in nature

Topic 1: Carbon and its compounds

1. Name the compound form heating ethanol at 443 K with excess of conc.H2SO4. 1

2. What happened when a small piece of sodium is dropped into ethanol ? 1

3. Write the chemical equation for the decarboxylation of ethanoic acid? 1

4. Give an example of esterification reaction. 1

5. Name the product obtained when ethanol is oxidized by either chromic anhydride or alkaline potassium permanganate. 1

6. Write the chemical equation repressing the preparation reaction of ethanol from ethane. 1.

7. Name the 2 elements which are present both in CNG and Petroleum 2

8. Draw the electronic dot structure of ethane molecule (C2H6) 2

9. Write the IUPAC name of the next homologous of CH3OHCH2CH3. 2

10.Define homologous series of organic compounds series of organic compounds ,Mention any two characteristics of homologous series. 2

11.Describe a chemical test to distinguish between ethanol and ethanoic acid. 2

12. Give the name of functional groups (i)-CHO (ii) –C=0 2

13.Why does carbon form compounds mainly by covalent bonding ? 2

14.Give a chemical test to distinguish ethanol from ethanoic acid. 2

15 Allotropy is a property shown by which class: substances elements compounds or mixtures ?

give one examples of allotropy. 2

16 . How may be the following be obtained from ethanol ? express giving chemical equations. (i) Ethyl ethanoate (ii) Sodium ethoxide. 2

17. Describe with chemical equation how ethanoic acid may be obtained from. (i) Ethanol (ii) Methanol 2

18. Explain the cleansing action of soap 3

19.Distinguish between esterification and saponification reactions of organic compounds 3.

20 Explain the structure of graphite in term of bonding and give one property based on this structure. 3

21 Name the organic acid present in vinegar .write a chemical equation which represents the commercial method for the preparation of this acid from methanol. 3

HIGH ORDER THINKING SKILLS (HOTS) QUESTIONS:

1. Why the colour of potassium permangante disappers,if it is added to warm solution of ethanol.

2. An organic compound with molecular formula C2H4O2 produces brisk effervescence on addition of sodium carbonate /bicarbonate.

a .Identify the organic compound.

b. Name the gas evolved.

C. How will you test the gas evolved.

d. Write the chemical equation for the above reaction.

e. List two important uses of the above compound.

3.a.What are the various possible structure formulae of a compound having molecular formula C3H6O .

b. Also give the IUPAC names of the above possible compounds.

c.What is the similarity in these compounds?

4.A mixture of oxygen and ethyne is burnt for welding ,can you tell why a mixture of ethyne and air is not used .

5.Two carbon compound A and B have molecular formula C3H8 and C3H6 respectively. Which one of the two is most likely to show addition .justify your answer .Explain with the help of a

chemical equation ,how an addition reaction is used in vegetable ghee industry. 

6.1ml glacial acetic acid and 1ml of ethanol are mixed together in a test tube. Few drops of concentrated sulphuric acid is added in the mixture are warmed in a water bath for 5 min.

a.Name the resultant compound formed.

b.Represent the above change by a chemical equation .

c.What term is given to such a reaction.

d.What are the special characteristics of the compound formed.

7.An organic compound ‗X‘with a molecular formula C2H6O undergoes oxidation in the presence of alkaline KMnO4 and forms the compound ‗Y‘.

a. Identify ‗X‘ and ‗Y‘

B.Write your observation when the compound ‗X‘ is made to react with compound ‗Y‘ which is used as a preservative for pickles

How Do Organisms Reproduce

Q. 1 A couple wants to space the birth of their second child. Suggest one preventive method which could be observed 

(a) By the husband (b) By the wife for the same.

Ans. (a) Use of condoms by the husband

        (b) Use of oral pills or loop or Copper-T by the wife.

Q. 2 A girl attains her puberty at the age of 11 years and a boy at 13 years but, still they are asked to refrain from sex, why? 

Ans. They are asked to refrain from sex because:-

       1. They are not physically, emotionally mature enough to be able to bear the responsibility of the child.

       2. They may suffer from reproductive tract infections.

Q.3 A pregnant woman visits a doctor to determine the sex of her child. The doctor refused to perform the test. Why is she being denied? 

Ans. The doctor refused to perform the test in order to prevent female foeticide which leads to an alarming decline in child sex ratio.

Q. 4 Blue prints of body design are stored in the DNA. Why? 

Ans. The chromosomes present in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA molecule. The DNA is the information source for making proteins. Thus, blueprints of the body design are stored in the DNA.

Q. 5 Producing individuals by parents consume a lot of energy. So, why should an individual organism waste energy in the process, it does not need to stay alive?

Ans. Reproduction, unlike other life processes is not essential to maintain the life of an individual organism. But it is essential for providing stability to the population of species. Maintaining the species is essential for maintaining balance in nature.

Q. 6 Protozoan reproduce by binary fission as well as by multiple fission. In your opinion which process is better and why? 

Ans. Multiple fission is better than binary fission because:-

       1. More number of individuals is produced.

       2. It helps to tide over unfavourable conditions.

MAGNETIC EFFECT

ORAL QUESTIONS

1. a) What are magnets?

b) What are natural magnets?

c) What is the meaning of the word lodestone?

d) What is the origin of the word magnetism?

2. a) State the law of magnetic poles.

b) What is the surer test of magnetism?

c) What happens if we break a magnet into two pieces?

d) Is it possible to obtain isolated north and south poles?

3. a) What is magnetic line of force?

b) Can two magnetic lines of force intersect? Give reason.

c) Magnetic lines of force are endless. Comment.

d) How do the field lines of the regions of strong field different from those of weak field?

4. a) What is a solenoid?

b) Is the magnetic field of a solenoid similar to that of a bar magnet?

c) State the two factors by which the strength of magnetic field inside a solenoid can be

increased.

d) How will you determine the direction of the magnetic field due to a current – carrying

solenoid?

5. a) What is an electromagnet?

b) What is the effect of placing an iron core in a solenoid?

c) What type of core should be used inside a solenoid to make an electromagnet?

d) Give two advantages of electromagnets.

ORAL QUESTIONS

1. What important observation did Oersted make in his experiments with current carrying

conductors?

2. How can you locate a current – carrying wire concealed in a wall?

3. A freely suspended magnet always points along north – south direction. Why?

4. What type of core should be used inside a solenoid to make an electromagnet?

5. Name the SI unit of magnetic field.

6. What is the principle of an electric motor?

7. A generator converts energy from one form to another. What is this energy conversion?

8. Which wire (live, neutral or earth) goes through the switch?

9. Are different appliances connected in series or parallel in a house?

10. What is the colour convention for live, neutral and earth wires?

PUZZLE

 AcrossÞ

1. A method preventing electric shock due to touching of live wire with the metallic body of

an appliance.

2. A device to convert electrical energy into mechanical energy.

3. A device to convert mechanical energy into electrical energy.

4. SI unit of magnetic field.

 Downß

5. A material having attractive and directive properties.

6. A temporary magnet.

7. A device to protect a circuit from overloading.

Chapter - 16

Management of Natural Resources

Q. 1 “White tiger has become an endangered species” why? 

Ans. White tiger has become an endangered species because of:

       a) Loss of habitat due to deforestation.

       b) Poaching by man

       c) or any other correct reason.

Due to this their number has decreased to such an extent that they are facing a threat

to their existence.

Q. 2 Why should we preserve bio diversity? 

Ans. If the bio- diversity is not preserved, the ecological stability of an area will be lost and ecological crisis will be caused.

Q. 3 What are “bio diversity hot spots”? Why this name has been given? 

Ans. Forests are called bio diversity hot spots because of the presence of a large number of species of plants and animals.

Q. 4 “Forests can not be conserved only by legislation; local human intervention is also required.” Justify your answer with two examples. 

Ans. The two examples when human intervention saved the forest are:

        1. The protection of Khajuri trees- In 1731 Amrita Devi Bishnoi led a group of 363 persons who sacrificed their lives for the protection of Khajuri trees in Khejrati village (Rajasthan).

        2. Hug the trees movement(Chipko Andolan)- In a Reni village in Gharwal when the contractor’s workers came into the forest to cut down the trees against the will of local people, the women of the village reached the forest quickly and clasped the trunks with their arms, and the forest trees were thus saved.

Q. 5 Which one is better to save an environment “Reuse” or “Recycling”? Give reasons to support your answer. 

Ans. “Reuse” of material is better than “Recycling” in saving our environment because:

         1. Reuse of material does not use any energy, whereas recycling uses some energy.

         2. In reuse things are used again and again instead of throwing away.