Students can access the CBSE Sample Papers for Class 10 Science with Solutions and marking scheme Term 2 Set 2 will help students in understanding the difficulty level of the exam.
CBSE Sample Papers for Class 10 Science Term 2 Set 2 with Solutions
Time allowed: 2 Hours
Maximum 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.
Answer the following questions:
(A) Menstruation is a monthly cycle in females. However, if fertilisation happens, menstruation will not occur. What changes can be expected if fertilisation does not occur? (1)
Answer:
The uterus prepares itself during every ovulation cycle in anticipation of a possible pregnancy. The lining of the uterus thickens so that it can give support to the developing embryo. When fertilisation does not occur, this lining disintegrates because it is no longer required. The fragments of the lining are shed along with blood and the discarded egg through the vagina. The discharge of discarded tissue is called menstruation.
(B) Sexually Transmitted Diseases are a real threat to the mankind. However, there are ways to prevent STDs. Can you give one example of STD caused by bacteria and virus each and suggest ways to prevent it. (1)
Answer:
Gonorrhoea is caused by bacteria and AIDS is caused by virus. These diseases can be prevented by responsible sexual behaviour such as use of condom during sexual intercourse, etc.
Question 2.
Answer the following questions:
(A) Why did Mendel choose garden pea plant for his experiments? Write two reasons. (1)
Answer:
Mendel choose garden pea plant for his experiments because:
- Pea plant has several contrasting characters like height, flower colour, seed colour and shape.
- Normally allows self pollination but cross pollination can also be done.
- It has short life span and also is easy to cultivate.
(B) List two contrasting visible characters of garden pea used by Mendel for his experiment. (1)
Answer:
Contrasting characters of garden pea plants:
- Colour of seeds:
- Dominant – Yellow
- Recessive – Green
Shape of seeds:
- Dominant – Round
- Recessive – Wrinkled.
Question 3.
Out of the two wires P and Q shown below which one has greater resistance? Justify it. (2)
OR
The voltage-current (V-l) graph of a metallic circuit at two different temperatures T
1
and T
2
is shown in figure. Which of the two temperatures is higher and why?
Answer:
It can be seen wire P has a length L and area of cross section A while the wire Q has a length of L and a area of cross section A/2. We know that resistance is directly proportional to length and inversely proportional to area of cross section. Hence the resistance of Q will be higher since its area of cross section is less than that of the wire P.
OR
We know that resistance of metals is directly proportional to the temperature. Higher temperature leads to higher resistance and vice-versa. In the graph T
2
has a higher resistance than T
1
hence the temperature T
2
is higher than T
1
.
Question 4.
(A) In the given figure, two hydrogen atoms in atomic state are given. Draw a diagram of a hydrogen molecule from the given diagram. (1)
Answer:
(B) Chlorine has an atomic number of 17. By what process/es will it be able to attain a noble gas configuration. Illustrate with the help of diagram. (1)
Answer:
Electronic configuration of chlorine is 2, 8, 7. it requires only one more electron to attain a noble gas configuration. It can do so either by sharing one electron with other chlorine atom and thus forming a chlorine molecule. Or it can accept an electron from an electropositive element such as group 1 or 2 metals and form an ionic compound. In either way, it will attain a noble gas configuration.
Caution:
Students may only identify with one method and miss the other interaction. Chlorine can adopt both mechanisms such as covalent interaction with another similar atom and ionic interaction with a metal. Be careful to mention both methods.
Question 5.
(A) Elements P, Q, R and S have atomic numbers 11,15,17 and 18 respectively.
| Element | Atomic Number |
| P | 11 |
| Q | 15 |
| R | 17 |
| S | 18 |
Identify which of them are reactive non-metals. Also, give reasons for your answer. (1)
Answer:
In order to understand the reactivity of elements, we need to first analyse the configuration of all elements.
| Elements | Atomic number | Electronic configuration |
| P | 11 | 2,8,1 |
| Q | 15 | 2,8,5 |
| R | 17 | 2,8,7 |
| S | 18 | 2,8,8 |
As can be seen from the table above, we can assess the elements as follows:
- P is a metal as it easily loose an electron to gain stability.
- Q is a non-metal as it can gain three electrons to gain stability.
- R is a non-metal as it can gain one electron to gain stability.
- S is an inert gas as it has a completely filled shell and is stable.
- Thus, amongst the above elements, R is the most reactive non-metal as it requires only one electron to attain stability and Q is also a reactive non-metal that requires only three more electrons to gain stability.
Related Theory:
A nonmetal is a chemical element that usually gains electrons when reacting with a metal, and which forms an acid if combined with oxygen and hydrogen. Nonmetals display more variety in colour and state than do metals. About half are coloured or colourless gases whereas nearly all metals are silvery-grey solids. They tend to be poor conductors of heat and electricity with no structural uses, in contrast to most metals.
Caution:
Students need to mention all the reactive non-metals by comparing their electronic configuration.
(B) The properties of eka-aluminium predicted by Mendeleev are the same as the properties of later discovered element. Which element took its place in the Modern Periodic table? (1)
Answer:
Gallium was the element that took the place of eka-aluminium. It has similar properties as compared to that of aluminium and fit properly in the gap left by Mendeleev.
Related Theory:
Mendeleev left some gaps in his Periodic Table. Instead of looking upon these gaps as defects, Mendeleev boldly predicted the existence of some elements that had not been discovered at that time. Mendeleev named them by prefixing a Sanskrit numeral, Eka (one) to the name of preceding element in the same group.
OR
(A) Name the neutral atom in the Periodic Table which has the same number of electrons as Na + and F – . Support your answer with suitable explanation. (1)
| Element | Ion |
| Na | NA + |
| F | F – |
Answer:
In order to identify the element, we need to write the electronic configuration of Na
+
and F
–
| Element/Ion | Electronic Configuration |
| Na | 2, 8, 1 |
| Na + | 2, 8 |
| F | 2, 7 |
| F – | 2, 8 |
As can be seen in the above table, the number of electrons in Na + and F – is 10 (2 + 8 = 10). The element with atomic number 10 is Neon which is an inert gas.
Related Theory:
Monoatomic ions are formed by the addition or removal of electrons from an atom’s valence shell. The inner shells of an atom are filled with electrons that are tightly bound to the positively charged atomic nucleus and so do not participate in this kind of chemical interaction, but the valence shell can be very reactive depending on the atom and its electronic configuration. The process of gaining or losing electrons from a neutral atom or molecule is called ionization.
Caution:
Students need to analyse the answer step by step and write the electronic configuration according to the charges as shown in the elements.
(B) An atom of an element has the electronic configuration 2, 8, 5. To which period and group does it belong? (1)
Answer:
The electronic configuration of the element is 2, 8, 5. A look at the configuration enables us to understand the valency of the element to be 3 as it can lose three electrons to gain stability.
As is evident from the configuration, the valence electron is present in M shell which is the third shell. Thus, the element belongs to the 3
rd
period.
As the number of valence electrons are 5, the element belongs to the 15
th
group owing to the ten transition elements that are present in 3
rd
period.
Thus, Period: 3
rd
Group: 15
th
Related Theory:
Groups and periods are two ways of categorizing elements in the periodic table. Periods are horizontal rows (across) the periodic table, while groups are vertical columns (down) the table. Atomic number increases as you move down a group or across a period.
Caution:
Students need to identify the shell with the period and valence electron with the group. They need to include the ten elements that are present between group 2 and group 13. Thus, the group no. wilt be 10 + 5 = 15 and not 5.
Question 6.
Female reproductive system has organs aligned in a way that facilitates formation and growth of foetus in it. In the given figure, label and identify the parts. (2)
(A) Site of fertilisation
(B) Production of eggs
(C) Site of implantation
(D) Entry of sperm
OR
What could be the importance and role of parts a, b and c in the given diagram?
Answer:
The internal structure of female reproductive system include the following parts:
(A) Fallopian tubes: The ova (egg cells) migrate from the ovaries to the uterus through the fallopian tubes, which are narrow tubes. An egg is fertilised by a sperm in the fallopian tubes.
(B) Ovaries: The ovaries are small oval-shaped glands in the female reproductive system that produce eggs and hormones.
(C) Uterus: The uterus (womb) is a hollow, pear-shaped organ that houses the developing foetus.
(D) Vagina: The vagina is a canal that connects the cervix to the outside world.
OR
a- Anther. It produces pollen grains which are the male gametes.
b- Style. It provides the path through which the pollen tube grows and reaches the ovary,
c- Ovary. It contains ovules and each ovule has an egg cell/female gamete. It develops into fruit after fertilisation.
Question 7.
‘The number of trophic Levels in a food chain is limited’. Justify the statement. (2)
Answer:
When green plants are eaten by primary consumers, a great amount of energy is lost as heat to the environment Some amount goes into digestion and in doing work and the rest goes towards growth and reproduction. Only 10 percent of the energy received by them is converted into their body mass which is available for the organisms of the next trophic levels. The longer the food chain, the less is the energy available to the final members of the food chain and that energy will be insufficient for their survival. So, the food chain is generally limited to 3-4 trophic levels only.
Section B
Question 8.
Shikhaj’s younger brother was playing with a magnet. Shikhaj advised him not to play with the magnet but his brother brought the magnet near the screen of the television that Shikhaj was watching. His TV got a permanent dark patch on the area where magnet was brought near the screen. His TV screen was partially damaged. Shikhaj immediately informed all his friends to be aware of such episodes at home.
(A) Why did TV get dark patch when magnet was brought closer? (2)
(B) Name two devices used at home which has electromagnetic effect in them. (1)
OR
Explain with the help of a labelled diagram the distribution of magnetic field due to current through a circular loop. Why is it that if a current carrying coil has n turns the field produced at any point is n times as large as that produced by a single turn? (3)
Answer:
(A) When a magnet was brought closer to the screen, the magnetic field of the magnet and the electromagnet in the T.V. interfered and spoiled its screen.
(B) DVDPlayerand Laptop has electromagnetic effect in them. A coil of wire wound around a bar of iron or other ferromagnetic material is an electromagnet. The coil and iron bar become magnetised when electric current travels through the wire.
Related Theory:
TV work or cathode rays which are fast moving electrons. Hence, in tree vicinity of a B-field the electrons lose their direction thereby changing or distorting the screen.
OR
In a current carrying circular loop direction of magnetic field lines can be found by the Right- Hand Thumb Rule. Thumb is showing direction of current and fingers show the direction of magnetic field lines. This means magnetic field lines are around the conducting wire. But circular shape of the conductor means that field lines at different points of the loop appear to be making many rings around the periphery of the loop. It can be visualized like many small rings looping around the periphery of a big ring. Effect of number of turns in a coiL we know that if number of turns in a coil is increased, then magnetic field will also increase. Due to this, strength of magnetic field increases with increased number of turns in a coil. Magnetic field lines through a circular loop are given below:
Question 9.
(A) Give the direction of induced current in the following figure. (1)
Answer:
The strength of the magnetic field is directly proportional to the relative closeness of field lines, therefore, region ‘a’ has a stronger magnetic field than region ‘b’.
Related Theory:
Poles: These are areas inside a magnet where the density of magnetic lines of forces is maximum.
Caution:
Many students erroneously believe that poles are where the field is maximum due to the poles being at the end. That is not true.
(B) Identify the poles of magnet in the figure. (1)
Answer:
The poles of a magnet are marked in the figure as we know that outside magnet field lines moves N → S and inside the Magnet field lines moves S → N.
Related Theory:
Magnetic lines of force form closed curves which emerge from N-pole of magnet and travels outside the magnet all the way to the S-pole whereas to complete the curve, the field entering the S-pole moves towards the N-pole inside the magnet
Caution:
Split/Slip rings are not for simple connection. They tend to create a continuous path in a rotating structure.
(C) A region ‘a’ has magnetic field lines relatively closer than another region ‘b’. Which region has a stronger magnetic field? Give a reason to support your answer. (1)
Answer:
Using Fleming’s right-hand rule.
- The direction of the induced current is anti-clockwise.
- The direction of the induced current is clockwise.
Question 10.
(A) What is the role of decomposers in the ecosystem? (1)
Answer:
The decomposers breakdown complex organic substances into simpler inorganic substances that go into the soil and are used again by the plants in the nutrient cycle.
Related Theory:
There will be no recycling of matter between biotic and abiotic components of an ecosystem, because all the matter will remain locked upon in the dead bodies. Thus, the existence of life on this earth will become impossible.
(B) Why is improper disposal of waste a curse to the environment? (1)
Answer:
Wastes pollute our environment, air, soil and water, and cause harmful effects on all living organisms.
(C) State the essential function performed by ozone at the higher levels of the atmosphere. (1)
Answer:
It shields the surface of the earth from ultraviolet (UV) radiation of the sun.
Related Theory:
Ozone layer depletiqn is one of the major problems for the atmosphere and also for all the living beings including the flora and fauna of this earth.
Question 11.
(A) An atom has electronic configuration 2, 8, 5. (2)
(i) Calculate the number of protons.
(ii) Is it a metal or non metal? Give reason.
Answer:
(i) The electronic configuration represents the arrangement of electrons in different shells. Thus, it also represents the total number of electrons in an element. Atomic number of an element is represented by number of electrons as well as number of protons.
Thus, number of protons is equal to 2 + 8 + 5 = 15 in the given atom.
(ii) As we can see the electronic configuration of atom is 2, 8, 5, the element requires only 3 more electrons to attain stability. The element can gain these 3 electrons to attain stability. Thus, the element behaves as a non metal as it gains electrons for attaining
Related Theory:
The nonmetals are located on the upper right side of the periodic table. Nonmetals are separated from metals by a line that cuts diagonally through the region of the periodic table. The nonmetals are in a minority on the periodic table, mostly located on the right-hand side of the periodic table. The exception is hydrogen, which behaves as a nonmetal at room temperature and pressure and is found on the upper left corner of the periodic table.
Under conditions of high pressure, hydrogen is predicted to behave as an alkali metal. Nonmetals have high ionization energies and electro negativities. They are generally poor conductors of heat and electricity. Solid nonmetals are generally brittle, with little or no metallic luster. Most nonmetals have the ability to gain electrons easily. Nonmetals display a wide range of chemical properties and reactivities.
Caution:
Students can get confused with the number of protons that has been asked in the question. In case ion is given instead of atom, there will be no change in the number of protons, but number of electrons will vary.
(B) An element Y with atomic number 7 reacts with oxygen to form a covalent oxide. Predict the nature of the oxide thus formed. Provide suitable explanation for your answer. (1)
Answer:
The element has atomic number 7, thus, the electronic configuration is 2, 5. The valency of element is 3. Electronic configuration of oxygen is 2, 6 and thus, its valency is 2.
Nature of the oxide: The element is a non metal as it belongs to group 15. The oxide thus formed is a non-metal oxide. Non metal oxides are acidic in nature.
Related Theory:
Non-metallic oxides are formed by the reaction of non-metals with oxygen. They react with a base to give salts and water. Let us consider the calcium hydroxide (base) reaction with carbon dioxide (non- metallic oxide) to produce salt and water.
Caution:
Identify the group of the element in order to classify the element as a non-metal
Question 12.
In order to attain a noble configuration, elements tend to either lose or gain electrons. This type of interaction leads to an ionic bond formation. On the other hand, few elements adopt to an entirely different mode of interaction where they share the electrons to attain a noble gas configuration.
(A) Which amongst the two mechanisms is adopted by carbon for attaining a noble gas configuration. (1)
(B) Why one method is preferred by carbon and the other mechanism is not feasible? (1)
(C) Based on this interaction, the compounds of carbon thus obtained are generally poor conductors of electricity. Explain. (1)
OR
(A) Identify the type of bond that is present between two identical non metallic atoms that shares an electron pair. (1)
(B) Amongst the homologous series in hydrocarbons, which one has the least number of hydrogen atoms? (1)
(C) In case of nitrogen molecule, determine the total number of electrons involved in bonding. (1)
Answer:
(A) Carbon adopts a mutual sharing of electrons, which is, covalent bond formation to attain a noble gas configuration.
(B) For ionic bond formation, the two pathways can be adopted.
1. If carbon loses 4 electrons, it becomes C4+. But it would require a large amount of energy to remove four electrons leaving behind a carbon cation with six protons in its nucleus holding on to just two electrons.
2. If carbon accepts 4 electrons, it becomes C
4-
. But it would be difficult for the nucleus with six protons to hold on to ten electrons, that is, four extra electrons.
Thus, it cannot form ionic interaction.
Due to these reasons, carbon adopts covalent interaction. It is feasible for carbon to share the electrons rather than transfer or accept the electrons.
(C) Carbon compounds are generally formed by covalent bond formation. Thus, it does not dissociate into ions. Thus, it is not possible to conduct electricity and thus are poor conductors of electricity.
OR
(A) A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding.
Caution:
Many students might get confused with non-metallic atoms. One needs to focus that elements of group 15, 16, 17 are known as purely non-metallic.
(B) Alkynes
Explanation: The general formula for alkynes is C
n
H
2n-2
. The general formula for alkanes is C
n
H
2n+2
and that of alkene is C
n
H
2n
Thus, with the help of the formula, least number of hydrogens is present in alkynes.
Related Theory:
A homologous series is a sequence of compounds with the same functional group and similar chemical properties in which the members of the series can be branched or unbranched, or differ by -CH
2
.
Caution:
Students might get confused with the number of carbon atoms instead of hydrogen atoms. They need to analyse it with the help of general formula of homologous series.
(C) 6 electrons
Explanation: Formation of nitrogen molecule involved triple bonding between the two nitrogen atoms. A single bond involves 2 electrons, therefore, three bonds equate to 6 electrons or 3 pairs of electrons.
Related Theory:
Nitrogen has five valence electrons, so it needs three more valence electrons to complete its octet. A nitrogen atom can fill its octet by sharing 3 electrons with another nitrogen atom, forming three covalent bonds, a so-called triple bond.
Caution:
Many students can give the answer 10 as they might give the total number of electrons involved in nitrogen molecule. The question specifically asks about bonding.
Question 13.
A woman has only daughters. Analyze the situation genetically and provide a suitable explanation. (3)
Answer:
A woman has only daughters. We know that the sex of the child is determined at the time of fertilization when male and female gametes fuse to form zygote. The male individual contains one X chromosome and one Y chromosome (XY) and the female individual contains two X chromosomes (XX).
If a sperm carrying X chromosome fertilizes an egg then the offspring will be a female child. This is because the offspring will have XX combination of sex chromosomes.
If a sperm carrying Y chromosome fertilizes an egg then the offspring will be a male child. This is because the offspring will have XY combination of sex chromosomes.
Thus the sex of the child is determined by the type of sperm that fuses with the ovum at the time of fertilization.
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.
Resistance is the property of a conductor to resist the flow of charges through it. The current which flows through a resistor is inversely proportional to its resistance, If the resistance is doubled the current gets halved. The resistance of the material depends on various factors. The resistivity of an alloy is generally higher than that of its constituent metals.
(A) A material has a resistivity of 10
-7
and the other has a resistivity of 10
-4
. Which of them is a better insulator? (1)
(B) A wire of resistance 10 ohm is stretched to four times its length. What will be its new resistance? (1)
(C) A student writes the equation p = \(\frac{1}{A}\) His friend pointed out that the equation is mathematically correct but physically not possible. Is his friend correct? Justify. (1)
OR
A charge of 10 coulombs is flowing through a wire for 10 minutes. If the work done is 10000 J what is the resistance of the wire? (1)
Answer:
(A) The materials with a resistivity 10
-7
has a lower resistivity and hence higher conductivity and hence it is a poorer insulator. That makes the other material with resistivity 10
-4
a better insulator owing to its higher resistivity.
(B) When a wire is stretched its length increases but its area decreases in proportion to the increase in length. This is due to the fact that the mass of the material remains constant which owing to its constant density means that the volume of the wire has to remain constant. Hence by stretching the wire to 4 times its length the area decreases by 4 times. Which means R = \(\frac{\rho l}{A}=\frac{\rho(4 l)}{A}=16 \frac{\rho l}{A}\). Hence the new resistance is 16 times higher than th original. So the new resistance is 160 Ohms.
(C) Mathematically any variable can be made to move around in an equation based on the availability of values of the other related variables. So mathematically it is correct. But when looked at it from the Physics point of view we see that the equation means that resistivity is proportional to resistance, area and length but that is not the case since in any material the resistivity is a constant quantity and does not depend on these three factors. Hence his friend is correct to point out that the equation is not.
OR
A charge of 10 coulombs is flowing through a wire for 10 minutes.
Given:
Q = 10 C,
t = 10 min = 600 s,
W = 10000 J.
We know that
W = Vlt
i = Q/t
and V = IR
When combined we get
W = Q
2
R/t
Hence R = Wt/Q
2
Hence R = 10000 × 600/100
= 60000 Ohms.
Question 15.
The sexual act always has the potential to lead to pregnancy. Pregnancy will make major demands on the body and the mind of the woman, and if she is not ready for it, her health will be adversely affected. A short survey was conducted in a city and the result of the survey is depicted in the form of pie chart below:
(A) Which diseases could be caused due to indulgence in unprotected sexual intercourse? (1)
(B) What do you think is the difference between miscarriage and abortion? (1)
(C) Prenatal sex determination has been prohibited by law. What could be the reason for this?
OR
Reproduction is linked to stability of population of a species. Do you think this statement is correct? Justify the statement. (2)
Answer:
(A) The disease include bacterial infections such as gonorrhoea and syphilis, and viral infections such as warts and HIV-AIDS.
(B) Miscarriage is the unintended loss of pregnancy. Abortion is the planned and intended termination of pregnancy.
(C) To lessen the indiscrimination of female foeticide, the Indian government has passed legislation prohibiting prenatal sex determination. As a result, in some parts of our culture, the child sex ratio has been dropping at an alarming rate. As a result, the child sex ratio must be maintained. Preventing crimes connected to a lower female ratio in society, such as female and child trafficking, sexual assault and abuse against women and children, increased maternal mortality owing to forced abortions, and early marriages, can be avoided in the long run by outlawing prenatal sex determination.
OR
Every species has a threat to its life due to various factors like predators, natural calamities, diseases, etc. The natural cycle of life and death also removes a section of the population. Reproduction is a way to replenish the lost section of population. Thus, it can be said that reproduction is linked to the stability of population of a species.
