SCIENCE - 2009
Comptt
Set - I -(Delhi
Comptt
Set - I -(
Time allowed : 2 1/2 hours
Maximum marks : 60
General Instructions :
(i) The question paper comprises of two Sections, A and B. You are to attempt both
the Sections.
(ii) All questions are compulsory.
(iii) There is no overall choice. However, internal choice has been provided in all the
three questions of five marks category. Only one option in such questions is to be
attempted.
(iv) All questions of Section A and all questions of Section B are to be attempted
separately.
(v) Questions number 1 to 6 in Section A and 17 to 19 in Section B are short answer
type questions. These questions carry one mark each.
(vi) Questions number 7 to 10 in Section A and 20 to 24 in Section B are short answer type questions and carry two marks each.
(vii) Questions number 11 to 14 in Section A and 25 and 26 in Section B are also short answer type questions and carry three marks each.
(viii) Questions number 15 and 16 in Section A and question number 27 in Section B are long answer type questions and carry five marks each.
(i) The question paper comprises of two Sections, A and B. You are to attempt both
the Sections.
(ii) All questions are compulsory.
(iii) There is no overall choice. However, internal choice has been provided in all the
three questions of five marks category. Only one option in such questions is to be
attempted.
(iv) All questions of Section A and all questions of Section B are to be attempted
separately.
(v) Questions number 1 to 6 in Section A and 17 to 19 in Section B are short answer
type questions. These questions carry one mark each.
(vi) Questions number 7 to 10 in Section A and 20 to 24 in Section B are short answer type questions and carry two marks each.
(vii) Questions number 11 to 14 in Section A and 25 and 26 in Section B are also short answer type questions and carry three marks each.
(viii) Questions number 15 and 16 in Section A and question number 27 in Section B are long answer type questions and carry five marks each.
Section A
Q. 1. Which gas is evolved when sodium hydrogen carbonate reacts with dilute hydrochloric acid? 1
Ans. CO2 gas is evolved when sodium hydrogen carbonate reacts with dilute hydrochloric acid.
Q. 2. Name the carbon compound which on heating with excess of concentrated sulphuric acid at 443 K gives ethene. 1
Ans. Ethanol on heating with excess of concentrated sulphuric acid at 443 K gives ethene.
Q. 3. Lithium, sodium and potassium form a Dobereiner’s triad. The atomic masses of lithium and potassium are 7 and 39 respectively. Predict the atomic mass of sodium. 1
Ans. The atomic mass of sodium is the arithmetic mean of the masses of lithium and potassium.
Therefore : 0.24 A current is flowing through 10 Ohm and 15 Ohm as current remains constant in series arrangements of resistors.
Ans. Heat produced, H = I2 x R x t joules Where I=Current, R=Resistance, t=time.
Q. 4. Redraw the diagram given in your answer book and show the direction of the light ray after reflection from the mirror. 1
Ans:
Q. 5. Two resistors of 10 Ohm and 15 Ohm are connected in series to a battery of 6 V. How do the values of current passing through them compare?
Solution :
Solution :
Therefore : 0.24 A current is flowing through 10 Ohm and 15 Ohm as current remains constant in series arrangements of resistors.
Q. 6. Write an expression for the heat produced H in time t in a heater of resistance R which is carrying a current I.
Q. 7. Describe an activity to demonstrate the change that takes place when white silver chloride is kept in sunlight. State the type of chemical reaction which takes place.
Activity :
(i) About 2 g of silver chloride is taken in a china dish. It is white in colour.
(ii) This china dish is placed in sunlight for some time.
(iii) It will be observed that white silver chloride turns grey due to formation of silver metal. This is a decomposition reaction.
(ii) This china dish is placed in sunlight for some time.
(iii) It will be observed that white silver chloride turns grey due to formation of silver metal. This is a decomposition reaction.
Q. 8. State two main properties of elements on which Mendeleev’s periodic classification was based. Why could no fixed position be assigned to hydrogen in his periodic table? 2
Ans. The two main properties of elements on which Mendeleev’s periodic classification was based:
(i) on the basis of the reaction of elements with hydrogen.
(ii) on the basis of the reaction of elements with oxygen.
No fixed position was given to hydrogen in Mendeleev’s periodic table because electronic configuration of hydrogen resembles that of alkali metals. So like alkali metals, hydrogen also combines with halogens,
oxygen and sulphur to form compounds having similar formulae.
(i) on the basis of the reaction of elements with hydrogen.
(ii) on the basis of the reaction of elements with oxygen.
No fixed position was given to hydrogen in Mendeleev’s periodic table because electronic configuration of hydrogen resembles that of alkali metals. So like alkali metals, hydrogen also combines with halogens,
oxygen and sulphur to form compounds having similar formulae.
Compounds of H | Compounds of Na |
HCI | NaCI |
H2O | Na2O |
H2S | Na2S |
On the other hand, just like halogens, hydrogen also exists as diatomic molecules and it combines with metals and non-metals to form covalent compounds.
Q. 9. Study the given diagram and answer the questions that follow: 2
(a) Which defect of vision is represented here? Give reason for your answer.
(b) Draw a ray diagram to show the correction of this defect by the use of a suitable lens.
(a) Which defect of vision is represented here? Give reason for your answer.
(b) Draw a ray diagram to show the correction of this defect by the use of a suitable lens.
Ans. (a) The defect is hypermetropia or far-sightedness because the image of nearby object lying at normal near point (at 25 cm) is formed behind the retina.
(b) See Q.1 (L.A.T), Chapter 11. [Page 129
Q. 10. Why does the sky look blue on a clear sunny day? Explain. 2
Ans. See Q.18 (S.A.T), Chapter 11.
Q. 11. State the name and function of the acid produced in our stomach. What remedy would you suggest to a person suffering from indigestion, pain and irritation in the stomach? Name the main ingredient of this remedy and state its function. 3
Ans. Our stomach produces hydrochloric acid. This dilute hydrochloric acid helps in digesting our food without harming the stomach. Sometimes excess acid is produced in the stomach due to various reasons like overeating. The excess acid in the stomach causes indigestion which produces pain and irritation. In order to cure indigestion, antacids are given.
Antacids are a group of mild bases which have no toxic effects on the body. As antacids are basic in nature so they neutralise the excess acid of the stomach and give relief to the person.
The two common antacids used for curing indigestion due to acidity are :
Magnesium hydroxide (milk of magnesia) and Sodium hydrogen carbonate (baking soda).
Antacids are a group of mild bases which have no toxic effects on the body. As antacids are basic in nature so they neutralise the excess acid of the stomach and give relief to the person.
The two common antacids used for curing indigestion due to acidity are :
Magnesium hydroxide (milk of magnesia) and Sodium hydrogen carbonate (baking soda).
Q. 12. Soap does not work well with hard water. Name the class of compounds which can be used as cleansing agents in place of soap. Write the name of one such compound. Explain in brief the echanism of its cleansing action when used in hard water. 3
Ans. Soap does not work well with hard water. This difficulty is overcome by using another kind of cleansing agent called detergents.
A detergent is the sodium salt of a long chain benzene sulphonic acid.
A common detergent is sodium n-dodecyl benzene sulphonate. Detergents can lather well even in hard water because they do not form insoluble calcium or magnesium salts on reacting with the calcium and magnesium ions present in hard water. A detergent works by making the oil and grease particles of dirty clothes dissolve in water through the formation of miscelles.
Q. 13. A student focussed the image of a candle flame on a white screen by placing the flame at various distances from a convex lens. He noted his observations in the following table:
An alloy of mercury metal with one or more other metals is known as an amalgam. e.g., a solution of sodium metal in liquid mercury metal is called sodium amalgam.
(b) The most widely used method for refining impure metals is electrolytic refining.
(c) Labelled diagram to show the refining of copper
Distance of the flame from the lens (cm) | Distance of the screen from the lens (cm) |
60 40 30 24 12 | 20 24 30 40 70 |
Analyse the above table and answer the following questions:
(a) What is the focal length of the convex lens?
(b) Which set of observations is incorrect and why?
(c) Draw a ray diagram to show the image formation for any correct set of observations. 3
(a) What is the focal length of the convex lens?
(b) Which set of observations is incorrect and why?
(c) Draw a ray diagram to show the image formation for any correct set of observations. 3
(a) Focal length of Convex lens = 15 cm.
(b) Case 5 is incorrect as per calculations.
(c) Ray diagram for Case 3 when the object is at 2F. See Q. 5, Case IV (L.A.T.), Chapter 10.
(b) Case 5 is incorrect as per calculations.
(c) Ray diagram for Case 3 when the object is at 2F. See Q. 5, Case IV (L.A.T.), Chapter 10.
Q. 14. Draw a circuit diagram to show an electric lamp of resistance 30 
and a resistor of 6 connected in series with a battery of 6 V. Calculate
(a) total resistance in the circuit
(b) current flowing through the circuit
(c) potential difference separately across the lamp and the resistor. 3
and a resistor of 6 connected in series with a battery of 6 V. Calculate(a) total resistance in the circuit
(b) current flowing through the circuit
(c) potential difference separately across the lamp and the resistor. 3
Q. 15. (a) What are ionic compounds? List any four physical properties of these compounds.
(b) What reaction happens when manganese dioxide is heated with aluminium powder? In which physical state is the metal produced in this reaction and why? 5
(b) What reaction happens when manganese dioxide is heated with aluminium powder? In which physical state is the metal produced in this reaction and why? 5
Ans. (a) The chemical bond formed by the transfer of electrons from one atom to another is known as an ionic bond and the compounds formed by such bonds are called ionic compounds.
Physical properties of ionic compounds:
1. Ionic compounds are usually crystalline solids because their oppositely charged ions attract one another strongly and form a regular crystal structure.
2. Ionic compounds have high melting points and high boiling points.
3. Ionic compounds are highly soluble in water.
4. Ionic compounds conduct electricity when dissolved in water or when melted because they contain charged particles i.e. ions.
1. Ionic compounds are usually crystalline solids because their oppositely charged ions attract one another strongly and form a regular crystal structure.
2. Ionic compounds have high melting points and high boiling points.
3. Ionic compounds are highly soluble in water.
4. Ionic compounds conduct electricity when dissolved in water or when melted because they contain charged particles i.e. ions.
(b) When manganese dioxide is heated with aluminium powder, manganese metal is produced
The reduction of manganese dioxide with aluminium is a highly exothermic reaction. A lot of heat is evolved therefore the manganese metal produced is in molten state.
Or
(a) What is an alloy? How does it differ from an amalgam?
(b) Name the method most widely used for refining impure metals.
(c) Draw a labelled diagram to show the refining of copper. 5
Ans. (a) An alloy is a homogeneous mixture of two or more metals (or a metal and small amounts of non-metals). The properties of an alloy are different from the properties of the constituent metals.(b) Name the method most widely used for refining impure metals.
(c) Draw a labelled diagram to show the refining of copper. 5
An alloy of mercury metal with one or more other metals is known as an amalgam. e.g., a solution of sodium metal in liquid mercury metal is called sodium amalgam.
(b) The most widely used method for refining impure metals is electrolytic refining.
(c) Labelled diagram to show the refining of copper
Q. 16. (a) State right hand thumb rule for finding the direction of magnetic field associated with a current carrying conductor. Draw a labelled diagram to show the experimental set-up for demonstrating the
rule. Mark the directions of the current and the associated magnetic field on the diagram.
rule. Mark the directions of the current and the associated magnetic field on the diagram.
(b) List two precautions which should be observed for the safety of the user and to avoid short circuiting in domestic circuits. 5
Ans. (a) Right hand thumb rule: See Q.3 (S.A.T.), Chapter 13. [Page 146 Diagram: See Q.14 (S.A.T.), Chapter 13. [Page 148
(b) Precautions which should be observed to avoid short circuiting in domestic circuits:
(i) Short circuiting can cause fires which can be highly damaging to electrical appliances and buildings. So, fuse of proper rating must be used to avoid such damages, as such a fuse-wire will melt before the temperature of the heated circuit wire gets too high and the circuit breaks.
(b) Precautions which should be observed to avoid short circuiting in domestic circuits:
(i) Short circuiting can cause fires which can be highly damaging to electrical appliances and buildings. So, fuse of proper rating must be used to avoid such damages, as such a fuse-wire will melt before the temperature of the heated circuit wire gets too high and the circuit breaks.
(ii) Old wiring should be checked regularly or changed when required.
Or
(a) What is a solenoid? Draw a labelled diagram to show the use of a current carrying solenoid to magnetise a steel rod. What is the nature of magnetic field lines inside a solenoid? What do these lines indicate?
(b) What is an electric fuse? What result do you expect if someone operates an electric heater of power rating 2 kW, 220 V in a domestic electric circuit (220 V) that has a fuse of current rating of 5 A? Justify your answer. 5
Ans. (a) A solenoid is a long coil containing a large number of close turns of insulated copper wire. The magnetic field produced by a current(b) What is an electric fuse? What result do you expect if someone operates an electric heater of power rating 2 kW, 220 V in a domestic electric circuit (220 V) that has a fuse of current rating of 5 A? Justify your answer. 5
carrying solenoid is similar to the magnetic field produced by a bar magnet. The magnetic field lines inside the solenoid are in the form of parallel straight lines. This indicates that the strength of magnetic field is the same at all points inside the solenoid. It is said to be a uniform magnetic field.
(b) An electric fuse is a safety device having a short length of a thin, tinplated copper wire having low melting point, which melts and breaks the circuit if the current exceeds a safe value. • Power of the electric heater,
Power of the electric heater,
P = 2 KW = 2 X 1000 W = 2000 W
Voltage, V = 220 V
P = 2 KW = 2 X 1000 W = 2000 W
Voltage, V = 220 V
An electric heater withdraws a 9·09 A current but the current rating of the fuse in the circuit is 5 A. Drawing a large quantity of current more than the capacity of fuse makes the fuse burn out. And thus a fuse in the circuit prevents damage to the appliance and the circuit due to overloading.
Section B
Q. 17. A young green plant receives sunlight from one direction only. What will happen to its shoots and roots? 1
Ans. (1) The roots bend away from light.
(2) The stem bends towards the light.
(2) The stem bends towards the light.
Q. 18. Mention the mode of reproduction used by (a) Amoeba (b) Planaria 1
Ans. (1) Amoeba → binary fission
(2) Planaria → regeneration
(2) Planaria → regeneration
Q. 19. What are the two kinds of natural resources? 1
Ans. Two kinds of natural resources are:
(1) Renewable
(2) Non-Renewable.
(1) Renewable
(2) Non-Renewable.
Q.20. Draw a diagram of a nerve cell (neuron) and label on it the following: 2
(a) Nucleus (b) Dendrites
(a) Nucleus (b) Dendrites
Ans. Diagram: See Q.1 (S.A.T.), Chapter 7. [Page 76
Q. 21. Name the information source of making proteins in the cell. State two basic events in reproduction. 2
Ans. The information source of making proteins in cell is DNA.
Two basic events in reproduction are:
(i) The creation of a DNA copy. Here the cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell.
(ii) DNA copying is accompanied by the creation of an additional cellular apparatus, and then the DNA copies separate, each with its own cellular apparatus. Effectively, a cell divides to give rise to two cells.
(i) The creation of a DNA copy. Here the cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell.
(ii) DNA copying is accompanied by the creation of an additional cellular apparatus, and then the DNA copies separate, each with its own cellular apparatus. Effectively, a cell divides to give rise to two cells.
Q. 22. List four advantages of using solar cells. 2
Ans. Advantages of using solar cells:
(i) They have no moving parts.
(ii) They require almost no maintenance.
(iii) They work quite satisfactorily even without using any light focussing device.
(iv) They can be set up in remote, inaccessible and very sparsely inhabited areas where the laying of usual power transmission lines is difficult and expensive.
(i) They have no moving parts.
(ii) They require almost no maintenance.
(iii) They work quite satisfactorily even without using any light focussing device.
(iv) They can be set up in remote, inaccessible and very sparsely inhabited areas where the laying of usual power transmission lines is difficult and expensive.
Q. 23. Name the major component of biogas. List two main advantages of using biogas over fossil fuels. 2
Ans. The major constituent of biogas is methane.
Advantages of biogas over fossil fuels:
(i) Biogas burns without smoke and hence does not cause air pollution.
(ii) Biogas burns completely without leaving behind any residue. So, it is a clean fuel.
Advantages of biogas over fossil fuels:
(i) Biogas burns without smoke and hence does not cause air pollution.
(ii) Biogas burns completely without leaving behind any residue. So, it is a clean fuel.
Q. 24. How is ozone formed in the upper atmosphere? Why is the damage of ozone layer a cause of concern to us? State a cause of this damage. 2
Ans. Ozone is formed high up in the atmosphere by the action of ultraviolet radiation on oxygen gas by the following process:
Step 1. The high energy UV radiation running from the sun splits oxygen gas into free oxygen atoms
Step 2. The free oxygen atoms thus produced are very reactive. One oxygen atom reacts with an oxygen molecule to form an ozone molecule.Step 1. The high energy UV radiation running from the sun splits oxygen gas into free oxygen atoms
This layer of ozone prevents the entry of harmful UV radiation to the earth’s surface, hence the damage to ozone layer is a cause of great concern to the mankind.
Chlorofluorocarbons (CFCs), which are used in refrigerants, deodrandts and in fire extinguishers, are one of the major causes of depletion of ozone layer.
Q. 25. Distinguish between acquired and inherited traits giving one example of each. Why are traits acquired during the lifetime of an individual not inherited?
Ans .
Acquired traits | Inherited traits |
1) A trait (or characteristic) of n organism which is ‘not inherited’ but develops in response to the environment is called an aquired trait. | 1) A trait (or characteristic) of an organism which is caused by a change in its genes (or DNA) is called an inherited trait. |
(2) The acquired traits of an organism can not be passed on to its future generations. e.g. ‘low weight’ of beetle, ‘cut tail’ of a mouse. | 2) The inherited traits of an organism are passed on to its future generations. e.g. red colour of beetles, fur coat of guinea pigs. |
Changes brought in the non-reproductive tissues can not be passed on to the DNA of the germ cells. So the experiences of an individual during its lifetime cannot be passed on to its progeny. Thus acquired characters of an individual cannot be inherited.
the DNA of the germ cells. So the experiences of an individual during its lifetime cannot be passed on to its progeny. Thus acquired characters of an individual cannot be inherited.
Q. 26. What is meant by exploitation of resources with short term aims? List its four advantages. 3
Ans. Exploitation of resources with short term aims means that management of natural resources is done in such a way so as to achieve short term gains which are enjoyed by just a handful of rich and powerful people. Resources are exploited to the hilt to meet the needs of the present generation without thinking of the needs of future generations.
Advantages:
(1) The main advantage of exploiting resources with short-term perspective is to get huge profit without any accountability.
(2) These resources fulfil the needs of present generation.
(3) Man gets a variety of raw materials from natural resources which are indispensable for the growth and development of our present day industries.
(4) It increases the (present day) growth rate of economy.
Advantages:
(1) The main advantage of exploiting resources with short-term perspective is to get huge profit without any accountability.
(2) These resources fulfil the needs of present generation.
(3) Man gets a variety of raw materials from natural resources which are indispensable for the growth and development of our present day industries.
(4) It increases the (present day) growth rate of economy.
Q. 27. (a) What is meant by breathing? What happens to the rate of breathing during vigorous exercise and why?
(b) Define translocation with respect to transport in plants. Why is it essential for plants? Where in plants are the following synthesised:
(i) Sugar (ii) Hormone 5
(b) Define translocation with respect to transport in plants. Why is it essential for plants? Where in plants are the following synthesised:
(i) Sugar (ii) Hormone 5
Ans. (a) Breathing. The mechanism by which organisms obtain oxygen from the air and release carbon dioxide is called breathing.
During vigorous exercise the demand of oxygen in the body tissues increases exponentially. Due to this, the rate of breathing increases during vigorous exercise.
(b) Translocation. The transport of food from the leaves to other parts of the plant is called translocation.
Leaves make food by the process of photosynthesis. The food made by leaves is in the form of simple sugar (glucose). Other type of substances called plant hormones are made in the tips of roots and
shoots. Every part of the plant needs food. So, food made in the leaves of a plant has to be transported (or carried) to all the different parts of the plant like branches, stem and roots etc.
(i) Sugar is synthesized in the leaves.
(ii) Hormones are synthesized in the tips of growing roots and shoots.
During vigorous exercise the demand of oxygen in the body tissues increases exponentially. Due to this, the rate of breathing increases during vigorous exercise.
(b) Translocation. The transport of food from the leaves to other parts of the plant is called translocation.
Leaves make food by the process of photosynthesis. The food made by leaves is in the form of simple sugar (glucose). Other type of substances called plant hormones are made in the tips of roots and
shoots. Every part of the plant needs food. So, food made in the leaves of a plant has to be transported (or carried) to all the different parts of the plant like branches, stem and roots etc.
(i) Sugar is synthesized in the leaves.
(ii) Hormones are synthesized in the tips of growing roots and shoots.
Or
Draw sectional view of the human heart and label on it the following chambers:
(i) Left atrium (ii) Right atrium (iii) Left ventricle (iv) Right ventricle State one function of each chamber in a tabular form. 5
(i) Left atrium (ii) Right atrium (iii) Left ventricle (iv) Right ventricle State one function of each chamber in a tabular form. 5
Ans. Diagram. See Q.27, Sample Paper II. [Page 19
Also add : (iv) Right ventricle—Send deoxygenated Blood to the lungs.
Also add : (iv) Right ventricle—Send deoxygenated Blood to the lungs.
No comments:
Post a Comment