Students can access the CBSE Sample Papers for Class 10 Science with Solutions and marking scheme Term 2 Set 8 will help students in understanding the difficulty level of the exam.
CBSE Sample Papers for Class 10 Science Term 2 Set 8 with Solutions
Time : 2 Hours
Max. Marks : 40
General Instructions :
- All questions are compulsory.
- The question paper has three sections and 15 questions. All questions are compulsory.
- Section-A has 7 questions of 2 marks each; Section-B has 6 questions of 3 marks each; and Section-C has 2 case based questions of 4 marks each.
- Internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
Section – A
Question 1.
What is the role of decomposers in the ecosystem? (2)
OR
Write the essential function performed by ozone at the higher levels of the Earth’s atmosphere? How is it produced? Name the synthetic chemicals mainly responsible for the drop of amount of ozone in the atmosphere.
Answer:
Decomposers act upon dead and decay organisms and convert them into simpler forms. These simple substances get mixed up in the soil and are used as nutrients by the producers. From producers it goes to consumers and so on. They maintain the balance in the ecosystem and provide space for new life in ecosystem.
OR
Ozone layer absorbs most of the harmful ultraviolet radiations from the sun to the earth. It is formed high up in the atmosphere by the action of ultraviolet radiation on oxygen gas. Chlorofluorocarbons are the synthetic chemicals responsible for the drop of amount of ozone in the atmosphere.
Question 2.
The electronic configuration of an element is 2, 8, and 4. State its:
(a) Group and period in the Modem Periodic Table.
(b) Name and write its one physical property. (2)
OR
What is Electronegativity?
Answer:
(a) If the configuration is 2, 8, 4 it means that it belongs to 3rd period and 14th group.
(b) The name of element is Silicon. It is a non-metal so, it is a poor conductor of electricity.
OR
Electronegativity is the tendency of an atom in a molecule to attract the shared pair of electrons towards itself. Electronegativity decreases in group from top to bottom. In a period, electronegativity increases from left to right because atomic size decreases.
Question 3.
How do Mendel’s experiment show that traits are inherited independently? (2)
Answer:
Mendel performed an experiment in which he took a tall plant with round seeds and short plant with wrinkled seeds. In Fa progeny all tall with round seeds were produced. Tallness and roundness were thus dominant traits. When he used these F1 progeny to generate F2 progeny by self-pollination, he found that some F2 progeny were tall plants with round seeds, while others were short, but had round seeds. Thus, Mendel’s experiment shows that tall or short traits and round or wrinkled seed traits are independently inherited.
Question 4.
Write the next homologue of each of the following: (2)
(a) C2H4
(b) C4H6
Answer:
(a) C3H6
(b) C5H8
Question 5.
(a) How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in the wire?
(b) Why does a current-carrying conductor experience a force when it is placed in a magnetic field? (2)
OR
Answer the following questions:
(a) Define magnetism.
(b) What do you mean by ‘magnetic field’ of a magnet?
Answer:
(a) Strength of magnetic field is directly proportional to the strength of current flowing in the wire.
(b) A current-carrying conductor produces a magnetic field around it. This magnetic field interacts with the externally applied magnetic field and as a result the conductor experiences a force.
OR
(a) The property by virtue of which a magnet attracts certain metals such as iron, cobalt, nickel etc., is termed as magnetism.
(b) The space or region around a magnet in which the force of attraction or repulsion due to the magnet can be detected is called the magnetic field.
Question 6.
Why is vegetative propagation practiced for growing some types of plants? (2)
Answer:
Vegetative propagation is practiced for growing some types of plants because:
- The plants which cannot produce seeds or produce non-viable seeds also can be easily propagated by this method.
- It is a very easy, quick and cheapest method of propagation.
- Seedless plants can be produced by vegetative propagation.
- Flowers and fruits are produced in very short time.
- Parental features are preserved.
Question 7.
List two functions of ovaries of human female reproductive system? (2)
Answer:
- Ovaries produces the ova or eggs and they produce hormones like oestrogen and progesterone.
- Oestrogen helps in development of secondary sexual characters in females at the time of puberty whereas progesterone prepares the uterus for receiving the fertilised egg.
Section – B
Question 8.
A blue flower plant denoted by BB is crossed with that of white coloured flower plant denoted by bb.
(a) State the colour of flower you would expect in their F1 generation plants.
(b) What must be the percentage of white flower plants in F2 generation if flower of F1 plants are self – pollinated?
(c) State the expected ratio of the genotypes BB and bb in the F2 progeny? (3)
Answer:
(a) In the first generation i.e. in F1, generation, all the flower plants will be of blue colour. It can be shown as follows:
(b) When flowers of F1 generation are self-pollinated:
So, in F2 generation, there will be three blue Flowers and one white flower. So the ratio of blue flower plant to ratio of white flower plant is 3 : 1 but we need to find the ratio percentage of white flower which is calculated as:
Percentage = \(\frac { Number of white flower plant }{ Total plants m F2 generation }\) x 100
Percentage = \(\frac { 1 }{ 2 }\) x 100
So, ratio percentage of white flower plant is 25%
(c) The expected ratio of the genotypes BB and Bb in the F2progeny is as follows:
Question 9.
Write the names given to the vertical columns and horizontal rows in the Modern Periodic Table. How does the metallic character of elements vary on moving down a vertical column? How does the size of atomic radius vary on moving left to right in a horizontal row? Give reason in support of your answer in the above two cases. (3)
OR
An element P (atomic number 20) reacts with an element Q (atomic number 17) to form a compound. Answer the following questions giving reason. Write the position of P and Q in the Modern Periodic Table and the molecular formula of the compound formed when P reacts with Q.
Answer:
Vertical columns in Modern periodic table are called groups and horizontal rows are called periods. As we move down the group metallic character increases as the atomic size increases, the force of attraction between nucleus and outermost shell decreases so tendency to lose ions increases. When we move left to right in a period, the number of electrons in the same shell increases leading to greater electrostatic attraction between nucleus and outermost electron. This increased attraction pulls the outermost electron closer to the nucleus, thereby decreasing the atomic size.
OR
P = 20: Electronic configuration 2, 8, 8, 2
Q = 17: Electronic configuration 2, 8, 7
P = Period 4 and Group 2
Q = Period 3 and Group 17
Hence formula of the compound formed between P and Q is PQ2.
Question 10.
You have been selected to talk on ‘Ozone layer and its protection’ in the school ‘Assembly on Environment Day’.
(a) Why should ozone layer be protected to save the environment?
(b) List any two ways that you would stress in your talk to bring in awareness among your fellow friends that would also help in protection of ozone layer as well as the environment. (3)
Answer:
(a) Ozone layer is present in stratosphere which prevents the ultra-violet rays from sun to penetrate the Earth’s surface. But due to depletion of ozone layer ultra-violet rays enter into the surface of Earth and cause many health hazards like skin cancer, cataract in eyes etc. So, it is necessary to save the environment by protecting the ozone layer.
(b) Some of the ways to protect the ozone layer are:
- Banning the use of CFC’s and other ozone depleting substances.
- Reducing the use of fluorescent lights, limited use of supersonic planes, control over large scale nuclear explosions etc.
Question 11.
What are covalent compounds? Why are they different from ionic compounds? List their three characteristics properties. (3)
Answer:
The compounds which are formed by sharing of electrons between two or more same atoms or between two or more non-metals are called covalent compounds. They are different from ionic compounds as:
- Covalent compounds are bad conductors of electricity whereas ionic compounds are good conductors of electricity in molten state.
- Covalent compounds are directional and ionic compounds are non-directional.
Characteristics of Covalent Compounds are:
- They have low melting and boiling point.
- These compounds are generally insoluble in water.
- These compounds are bad conductors of electricity.
Question 12.
Answer the following questions: (3)
(a) List the factors on which the resistance of a conductor in the shape of wire depends.
(b) Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason.
(c) Why is lead-tin alloy used for fuse wires?
Answer:
- Resistance of a conductor depends directly on its length and is inversely proportional to the area of cross-section.
- Metals have free electrons and they move and conduct electricity, whereas glass does not have free electrons and charges to flow as it is an insulator.
- Lead-tin alloy is used for fuse wires because it has low melting point. It will melt when high supply come to prevent the electric circuit from fire.
Question 13.
The wire in the figure below is being moved downwards through the magnetic field, so as to produce induced current.
What would be the effect of:
(a) moving the wire at a higher speed?
(b) moving the wire upwards rather than downwards?
(c) using a stronger magnet? (3)
OR
(a) When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
(b) State the condition in each case of the magnitude of force on a current carrying conductor placed in a magnetic field to be (i) zero and (ii) maximum.
Answer:
(a) The induced current increases at a higher speed.
(b) The induced current is reversed.
(c) The induced current increases.
OR
(a) The force experienced by a current-carrying conductor placed in a magnetic field is largest when the current-carrying conductor is placed perpendicular to the direction of magnetic field.
(b) (i) The magnitude of force acting on a current carrying conductor placed in a magnetic field will be zero, when the current carrying conductor is in the direction of magnetic held.
(ii) The magnitude of force acting on a current carrying conductor placed in a magnetic held will be maximum, when the current carrying conductor is normal (perpendicular) to the magnetic field.
Section – C
This section has 02 case-based questions (14 and 15). Each case is followed by 03 sub-questions (a, b and c). Parts a and b are compulsory. However, an internal choice has been provided in part c.
Question 14.
(a) Write three points of difference between Ohmic resistor and non-Ohmic resistor.
(b) Write two points of difference between resistance and resistivity (or specific resistance).
(c) Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 Ω resistor, an 8 Ω resistor, and a 12 Ω resistor and a plug key, all connected in series. Now, connect the ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the 12 Ω resistors. What would be the readings in the ammeter and the voltmeter? (4)
OR
Calculate the equivalent resistance of the following network :
Answer:
(a)
Ohmic Resistor | Non-Ohmic Resistor |
1. Ohmic resistors obey Ohm’s law. | Non-Ohmic resistors do not obey Ohm’s law. |
2. The graph for potential difference (V) versus current (I) is a straight line. | The graph for potential difference (V) versus current (I) is not a straight line. |
3. The slope of V-I graph is constant at all values of V or I at a given temperature. | The slope of V-I graph is different at different values of V or I even at a given temperature. |
(b)
Resistance | Resistivity (or Specific Resistance) |
The S.I. unit of resistance is Ohm (Q). | The S.I. unit of resistivity is ohm-metre (Ω m). |
Resistance of a substance depends on its length and thickness. | Resistivity of a substance is independent of its length and thickness. |
(c) The total resistance of the circuit is given by
R = 5 + 8 + 12
= 25 Ω
We know, R = \(\frac { V }{ 1 }\)
Hence, 25 = \(\frac { 6 }{ I }\)
I = \(\frac { 6 }{ 25 }\)
= 0.24 A
Since, resistance are connected in series, thus electric current remains the same through all resistors. Here we have,
Electric current, I = 0.24 A
Resistance, R = 12 Ω
Thus, potential difference (V) through the resistor of 12 Ω is given by
V = I x R
= 0.24 x 12 = 2.88 V
∴Reading of ammeter = 0.24 A
Reading of voltmeter through resistance of 12 Ω = 2.88 V.
OR
Let Rp is the equivalent resistance of resistors connected in parallel.
∴ Equivalent resistance of the circuit
Now, equivalent circuit becomes.
∵ 10 Ω and 10 Ω are connected in series.
∴ Equivalent resistance of the circuit
R = 10 Ω + 10 Ω
= 20 Ω
Question 15.
Historically, the evolutionary origins of menstruation have been based on two theories: the ability to eliminate infectious agents carried to the uterus with spermatozoa and the comparative conservation of energy with menstruation compared to its absence. Menstruation, is the shedding of the superficial endometrium with associated bleeding, occurs in some species of placental mammals when progesterone levels fall at the end of an infertile reproductive cycle.
(a) What is the need for menstruation in human beings?
(b) Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?
(c) What are the common side-effects of using contraceptive pills? (4)
OR
Describe the role of the following in a male reproductive system and label them in a figure:
(i) Testis
(ii) Vas deferens
Answer:
(a) Menstruation is the monthly cycle in the female reproductive system where the unfertilised egg is shed along with the uterine lining once in 28 days. The female germ cells or eggs are made in the ovary. One egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through the fallopian tube. The egg lives for about a day if it is not fertilised. As the ovary produces, one egg per month the uterus also prepares itself to receive a fertilised egg every month. So, it develops a thick and spongy lining. This would help to nourish the embryo. When fertilisation does not occur, this lining is not needed any more. It breaks and slowly comes out through the vagina as blood and mucous. The menstrual cycle lasts for about three to five days. Thus, menstruation is necessary to get rid of the unfertilised egg and prepare the next egg and uterus for a possible fertilisation and pregnancy.
(b) Yes, we agree with this statement that only variations that confer an advantage to an individual organism will survive in a population because those variations which occur in an individual that favours the organism to get adapt to the environment will be able to survive otherwise it may not. The chances of survival depend upon the nature of variations. Different individuals would have different kinds of advantages. For example: A bacteria which can withstand heat will be able to survive in hot springs otherwise it will die. Selection of variants by environmental factors forms the basis for evolutionary process.
(c) The common side effects of using contraceptive pills are irritation, nausea and mood swings.
OR
(i) Testes are the primary sex organs in a human male which produce sperms by the process of spermatogenesis. They also produce male sex hormone testosterone which helps in the development of secondary male characteristics at the time of puberty.
(ii) Vas deferens also called sperm ducts carries the sperms from testes to urethra.