Question 1 ( 1.0 marks)
How many moles of oxygen are present if there are No oxygen molecules?
Solution:
Question 2 ( 1.0 marks)
Name any two kingdoms having multicellular organisms with cell wall.
Solution:
Fungi and plants are the two kingdoms having multicellular organisms with cell wall.
Question 3 ( 1.0 marks)
A particular kingdom X has organisms with cell wall, but a non-definite nucleus. Identify the kingdom X.
Solution:
Kingdom Monera has organisms with cell wall, but a non-definite nucleus.
Question 4 ( 1.0 marks)
In lifting an object, gravitational force is said to have done negative work. Why is it so?
Solution:
The work done in this case is negative because the displacement of the object is directed opposite to the line of action of gravitational force.
Question 5 ( 1.0 marks)
How is a mechanical wave carried forward in a medium if there is no forward motion of the particles of the medium?
Solution:
A mechanical wave is a disturbance that causes particles of a medium to move back and forth about their original position. Their back-and-forth movement sets neighbouring particles into similar motion and so on. This is how a wave propagates through the medium.
Question 6 ( 2.0 marks)
Derive the chemical formula of calcium hydrogen carbonate.
Solution:
For calcium hydrogen carbonate, the symbol of cation or calcium ion is Ca2+ and the symbol of anion or hydrogen carbonate is
 .
Thus,
Hence, the chemical formula of calcium hydrogen is Ca(HCO3)2.
Question 7 ( 2.0 marks)
What is the number of molecules of ammonia in 5.1 g of ammonia?
Solution:
Mass of 1 mole of ammonia (NH3) or molar mass of ammonia is 17 g.
1 mole of ammonia contains 6.022 ×1023 moles of NH3.
Or, 17 g of ammonia contains 6.022 × 1023 molecules of NH3.
5.1 g of ammonia contains
 molecules of NH3.
i.e., 18.066 × 1022 molecules of NH3
Hence, the number of molecules of ammonia in 5.1 g of ammonia are 18.066 × 1022.
Question 8 ( 2.0 marks)
An atom with a mass number and atomic number of 108 and 50 respectively disintegrates to form an atom having mass number and atomic number of 106 and 50 respectively. What is the number of electrons, protons, and neutrons present in the new atom?
Solution:
The number of protons and electrons in an atom is equal to the atomic number of the atom. The number of neutrons is calculated as the difference between the mass number and the atomic number of the atom. Thus, the number of protons and electrons present in the atom after disintegration is equal to 50. The mass number of the atom reduces to 106.
Therefore, number of neutrons = 106 − 50 = 56
Question 9 ( 2.0 marks)
Define the following terms.
(a). Isotopes
(b). Isobars
Solution:
(a). Isotopes are defined as the atoms of the same element, having the same atomic number, but different mass numbers.
(b). Isobars are defined as the atoms of different elements with different atomic numbers, which have the same mass number.
Question 10 ( 2.0 marks)
Classification helps us in predicting the line of evolution. Justify.
Solution:
This The slow change in the body design of an organism over a long period of time is termed as evolution. It helps an organism to survive in its surroundings. Classification allows things to be identified and categorised on the basis of structure and function of an organism and accordingly, they can be referred as primitive or advanced organisms. This helps in predicting the line of evolution.
Question 11 ( 2.0 marks)
What are the two essential conditions that must be satisfied in order to say that work is done on a body?
Solution:
The two essential conditions for considering that work is done on a body are:
(i) A force must act on an object.
(ii) The object must have a displacement along the line of action of the applied force.
Question 12 ( 2.0 marks)
How are the motions of the particles propagating light waves and sound waves different?
Solution:
In case of sound wave propagation, individual particle of a medium moves to and fro about its mean position along the direction parallel to the direction of propagation of the disturbance.
In case of light wave propagation, individual particle oscillates up and down about its mean position. The direction of movement of each particle, in this case, is perpendicular to the direction of propagation of the wave.
Question 13 ( 2.0 marks)
Organs affected by microbes depend on the site of their entry. State suitable examples to justify this statement.
Solution:
Microbes affect specific organs depending on the site of their entry. This statement can be justified with the help of following examples:
Question 14 ( 2.0 marks)
A certain area has four different regions, I, II, III, IV. The air from region IV flows toward region I. The air from region IIIflows toward region I. The air from region I flows toward region II. Which region has maximum temperature? Explain.
Solution:
Region II has maximum temperature. Air moves from region IV to region I. Therefore, region I is hotter than region IV. Air moves from region III to region I. Therefore, region I is hotter than region III. Finally, air moves from region I to region II. Therefore, region II is hotter than region I. Hence, region II has maximum temperature.
Question 15 ( 3.0 marks)
Calculate the formula unit mass of the following compounds.
(a). Sodium oxide
(b). Calcium chloride
Solution:
(a). The formula unit of sodium oxide is Na2O.
The formula unit mass of any substance is equal to the sum of the mass of all atoms present in a formula unit of that substance.
Atomic mass of sodium (Na) = 23 u
Atomic mass of oxygen (O) = 16 u
Formula unit mass of Na2O = (2 × 23 + 1 × 16) u = (46 + 16) u = 62 u
Hence, the formula unit mass of sodium oxide is 62 u.
(b). The formula unit of calcium chloride is CaCl2.
The formula unit mass of any substance is equal to the sum of the mass of all atoms present in a formula unit of that substance.
Atomic mass of calcium (Ca) = 40 u
Atomic mass of chloride (Cl) = 35.5 u
Formula unit mass of CaCl2 = (1 × 40 + 2 × 35.5) u = (40 + 70) u = 110 u
Hence, the formula unit mass of calcium chloride is 110 u.
Question 16 ( 3.0 marks)
The given table lists some atoms and the number of electrons, protons, and neutrons present in them.
(a). Which of the given elements form a pair of isobars?
(b).Which of the given pairs forms a pair of isotopes?
Solution:
(a). Isobars are atoms of different elements having the same mass number.
Atomic number of an atom is equal to the number of protons present in it. Therefore, the atomic number of potassium is 19 and the atomic number of calcium is 20.
Mass number of an atom = Number of protons + Number of neutrons
Thus, mass number of potassium = 19 + 21 = 40
Mass number of calcium = 20 + 20 = 40
Potassium and calcium have the same mass number of 40. Hence, they are isobars.
(b). Isotopes are atoms of the same element having different mass numbers. As isotopes have a different atomic mass, they have different physical properties.
The two chlorine atoms given in the table have same number of protons but different number of neutrons. Hence, they are isotopes.
Question 17 ( 3.0 marks)
Compare and contrast roundworms with flatworms.
Solution:
Points of comparison between roundworms and flatworms:
Points of contrast between roundworms and flatworms:
Question 18 ( 3.0 marks)
Name the devices or machines which convert
(i) chemical energy into heat energy
(ii) light energy into heat energy
(iii) heat energy into kinetic energy
What must be the power of the brakes of a car for them to stop the car moving at a velocity of 60 km/h, weighing 1500 kg?
Solution:
(i) In a gas stove, chemical energy is converted into heat energy. Cooking gas is burnt in a gas stove to produce heat energy.
(ii) In a solar water heater, light energy is converted into heat energy. Solar water heater traps sunlight and produces heat.
(iii) In a steam engine, heat energy is converted into kinetic energy. In a steam engine, heat is used for boiling water and for obtaining steam under high pressure to turn a shaft and drive the wheels.
Question 19 ( 3.0 marks)
Starting from the third equation of motion, derive the expression for kinetic energy.
Solution:
It is known that the third equation of motion is:
v2 − u2 = 2as (Where v = Final velocity, u = Initial velocity, a = Acceleration, s = Distance)
Oror, s
 … (1)
Force, F = ma (where m = mass)
Thus, equation (1), multiplied on both sides with F, may be written as:
  m (v2 − u2)
If the object in its starting position was stationery i.e., u = 0
Oror,
Work done
 Ability of the body to do work by virtue of its motion
Thus, the kinetic energy possessed by a body of mass m and velocity v is
 .
Question 20 ( 3.0 marks)
(a). What characteristic of a sound wave changes when it propagates from one medium to another?
(b). How will you demonstrate the same?
Solution:
(a). The speed of a sound wave changes when it propagates from one medium to another.
(b). The change of speed of sound when it enters from one medium to another can be demonstrated as follows:
If a person beats one end of a very long iron rod hard enough to produce a sound, then another person with ear pressed to the other end of the rod will be able to hear two sounds—one that travels through the rod and the other through the air. However, the second person will not hear the two sounds at the same time. Since sound travels faster through a solid, the sound travelling through the rod will be heard first.
This experiment proves that the speeds of sound are different in different media.
Question 21 ( 3.0 marks)
(a). How are ultrasounds useful in detecting structural flaws inside solid metal blocks?
(b). Why cannot ordinary sound waves be used for the same?
Solution:
(a). Ultrasonic waves are made to pass through the metal block and are received by detectors at the other end. If they meet any structural defect inside the block, then the waves get reflected and are not received by the detector at the other end, thus indicating the presence of flaw.
(b). Normal sound waves have long wavelengths. Therefore, they cannot enter into a metal body; rather they get reflected from the metal surface. On the other hand, ultrasound being a short-wavelength sound can easily penetrate metal body. Thus, ordinary sound cannot be used for detecting flaws in a metal block.
Question 22 ( 3.0 marks)
Describe the different types of eukaryotic infectious agents.
Solution:
Eukaryotic infectious agents fall under three main categories, which are described as follows:
Question 23 ( 3.0 marks)
(a). What role is played by water in soil formation?
(b). How does plant help in maintaining the quality of top soil?
Solution:
(a). Water enters the rocks through the cracks in them. When temperatures fall, water freezes. As ice occupies more space than water, the crack expands when water freezes. This expansion eventually leads to breaking down of rocks. Another way in which water helps in the formation of soil is when running water flows along rocks. The flow of water along the rocks creates a friction between water and rocks, which results in the weathering of rocks. This leads to the formation of soil.
The soil thus formed may flow along with the water and get deposited elsewhere.
(b). Roots of plants hold the soil tightly and prevent soil erosion. Consequently, humus containing fertile top soil is not carried away by the action of moving air and water. Therefore, plants play a very important role in maintaining the quality of top soil.
Question 24 ( 4.0 marks)
(a). How can an
 ion be classified?
(b). For what kind of compounds can the concept of formula unit be used? Give an example.
(c). Derive the chemical formula for milk of magnesia?
Solution:
(a).
represents a polyatomic anion. Clusters of atoms that act as an ion are called polyatomic ions. Also, as it carries a net negative charge, it is an anion.
(b). The concept of formula unit is used in the case of a compound whose constituent particles are ions i.e., ionic compounds such as NaCl.
(c). Milk of magnesia or magnesium hydroxide is composed of magnesium and hydroxide ions. Magnesium ions are represented by Mg2+ and hydroxide ions are represented by OH−.
On exchanging the valencies,
Thus, the chemical formula of
milk of magnesia is Mg(OH)2.
Question 25 ( 4.0 marks)
Answer the following questions.
(a). How does cellularity prove to be a basic criterion for classification?
(b). What is meant by hierarchy of classification? Give a schematic representation of the hierarchy and briefly explain the basic ranks involved in the hierarchy.
(c). Classification throws light on the evolutionary history of an organism. Justify this statement.
Solution:
(a). Unicellular organisms are those organisms whose body is made up of a single cell whereas multicellular organisms are those organisms whose body is made up of many cells. Multicellular organisms use the principle of division of labour to perform specialised functions. This results in a specific body design that distinguishes multicellular organisms from unicellular organisms.
(b). Hierarchy refers to the organisation or classification of things in order of rank or importance.
, Family, and Genus. Then finally, each Genus is divided into Species. This hierarchy can be schematically represented as:
(c). Most of the life forms seen today have arisen from the accumulation of changes in the body design of ancient organisms. This slow change in the body design of an organism over a long period of time is termed as evolution.
Classification allows things to be identified and categorised on the basis of structure and function of an organism and accordingly, they can be referred as primitive or advanced organisms. This helps in predicting the line of evolution.
Question 26 ( 4.0 marks)
(a). Using pressure-time graphs, differentiate between the following:
i. Sharp and flat sounds
ii. Soft and loud sounds
(b). A sound wave has a frequency of 5 kHz and wavelength of 20 cm. How long will it take to travel 2 km? Will it be audible to a man standing there?
Solution:
(a). (i) Flat:-
(ii) Soft:-
(b). Given that:
Frequency, ν = 5 kHz = 5,000 Hz
Wavelength, λ = 20 cm = 0.20 m
Speed (v) of a sound wave is related to its wavelength and frequency as:
speed, v = νλ
= 5,000 × 0.20
= 1,000.0 m/s
Also,
Given that distance = 2 km = 2,000 m
We haveTherefore, time
 
= 2 s
The sound will take 2 s to travel 2 km.
A man standing there will be able to hear the sound since its frequency (5,000 Hz) is within the range of audible frequencies (20−20,000 Hz) for humans.
Question 27 ( 1.0 marks)
Which of the following devices does not involve the principle of multiple reflection of sound for its functioning?
A.
Horn
B.
Drum
C.
Megaphone
D.
Stethoscope
Solution:
Drum is a musical instrument. It does not produce sound due to multiple reflection of sound. Sound is produced in it by the vibration of its stretched surface or membrane when it is beaten.
The correct answer is B.
Why alternatives A, C, D are wrong:
Megaphone, stethoscope, and horn send sound wave in a particular direction by the phenomenon of multiple reflections. Sound wave reflects from the wall of these devices again and again to travel inside them. This enhances the amplitude of the produced sound.
Question 28 ( 1.0 marks)
Which of the following statements is incorrect for isobars?
A.
Isobars have different mass numbers
B.
Isobars have different atomic numbers
C.
Isobars have different number of neutrons
D.
Isobars have different number of electrons
Solution:
Isobars are atoms of different elements having the same mass number.
For example,
 and  are a pair of isobars. The atomic number of potassium and argon is different, but both have the same mass number of 40.
The correct answer is A.
Why alternatives B and D are wrong:
Isobars are atoms of different elements. Hence, they have different atomic numbers. Since they have different atomic numbers, they have different number of protons and electrons.
Why alternative C is wrong:
Isobars have different number of neutrons. For example,
and have different number of neutrons of 21 and 22 respectively.
Question 29 ( 1.0 marks)
The number of moles present in 66 g of carbon dioxide is
A.
0.5 mol
B.
1 mol
C.
1.5 mol
D.
2 mol
Solution:
Molar mass of carbon dioxide (CO2)
1 mol of CO2 = 44 g of CO2
Number of moles of CO2 present in 44 g of CO2 = 1 mol
The correct answer is C.
Question 30 ( 1.0 marks)
The number of nitrate ions present in 14.8 g of magnesium nitrate is
A.
3.011 × 1023
B.
6.022 × 1022
C.
9.033 × 1023
D.
12.044 × 1022
Solution:
Mass of 1 mole of magnesium nitrate
Then, 148 g of [Mg(NO3)2] contains = 6.022 × 1023 molecules of [Mg(NO3)2]
1 molecule of
 contains  ions
Hence, the number of nitrate ions present in 14.8 g of magnesium nitrate is 12.044 × 1022.
The correct answer is D.
Question 31 ( 1.0 marks)
Use the following information to answer the next question.
The information in which alternative correctly represents the name of the elements X and Y?
A.
B.
C.
D.
Solution:
The atom of the element X has a total of 17(2 + 8 + 7) electrons. That is, the atomic number of X is 17.
Hence, the element X is chorine. The atom of the element Y has a total of 5 (2 + 3) electrons. That is, the atomic number of Y is 5.
Hence, element Y is boron.
The correct answer is C.
Why alternatives A, B and D are wrong:
The schematic atomic structures of fluorine and aluminium are
Question 32 ( 1.0 marks)
Which of the following statements is incorrect?
A.
Rutherford proposed that in an atom, the electrons are embedded in a positively charged sphere.
B.
According to Bohr, electrons revolve around the nucleus in some discrete orbits known as energy levels.
C.
Thomson proposed that an atom is electrically neutral because of the equality in magnitude of the positive and negative charges.
D.
Bohr and Bury proposed the distribution of electrons into different orbits.
Solution:
The said model was proposed by Thomson and not by Rutherford.
Rutherford proposed the following.
(i) In an atom, there is a positively charged centre called nucleus. Nearly all the mass of an atom resides in the nucleus.
(ii) The electrons revolve around the nucleus in well-defined orbits.
(iii) The size of the nucleus is very small as compared to the size of the atom.
The correct answer is A.
Why alternatives B, C and D are wrong:
The statements given in the alternatives B, C, and D are correct.
Question 33 ( 1.0 marks)
Use the following information to answer the next question.
Which process is being referred to?
A.
Evaporation
B.
Precipitation
C.
Denitrification
D.
Nitrogen fixation
Solution:
Nitrogen is essential to life as it is a part of proteins, DNA, RNA, urea, alkaloids, etc. Atmospheric nitrogen is fixed by nitrogen fixing bacteria. It is also fixed by physical processes such as lightening. The given information describes how lightening helps in fixing nitrogen in the soil with the help of rain.
The correct answer is D.
Why alternative A is wrong:
Evaporation is the loss of water in the form of water vapours.
Why alternative B is wrong:
When clouds no longer withstand the gravitational pull of the earth, they fall in the form of rain. The process is called precipitation.
Why alternative C is wrong:
The fixing of nitrogen present in the soil, animals, and plants back in the atmosphere is known as denitrification.
Question 34 ( 1.0 marks)
Use the following information to answer the next question.
The information in which row completes the given statement?
A.
B.
C.
D.
Solution:
Sound waves are disturbances in a medium that move through it when the particles in the medium set neighboring particles in motion. These waves are mechanical waves that travel by disturbing the particles in the medium in the direction parallel to their direction of propagation.
In longitudinal waves, the particles in the medium do not move from one point to another but oscillate back and forth from their mean positions. This means that they oscillate along the direction of wave motion. Hence, a longitudinal wave has vibrations in the direction parallel to the direction of wave propagation.
It can be concluded from the discussion that sound waves are longitudinal waves and their vibrations are parallel to the direction of wave propagation.
The correct answer is B.
Question 35 ( 1.0 marks)
Which diagram correctly represents the motion of particles in longitudinal waves?
A.
B.
C.
D.
Solution:
In longitudinal waves, individual particles vibrate in the direction parallel to the direction of propagation of the disturbance. This is correctly represented by the diagram given in alternative A.
The correct answer is A.
Question 36 ( 1.0 marks)
Which of the following elements exists as a diatomic molecule?
A.
Argon
B.
Helium
C.
Oxygen
D.
Sulphur
Solution:
A molecule of oxygen consists of two atoms of oxygen. Hence, it exists as a diatomic molecule.
The correct answer is C.
Why alternatives A and D are wrong:
Argon and helium are inert gases. Molecules of these elements are made up of only one atom of that element. Hence, argon and helium are monoatomic.
Why alternative B is wrong:
A molecule of sulphur consists of eight atoms bonded together. Hence, sulphur is polyatomic.
Question 37 ( 1.0 marks)
Which of the following statements about pteridophytes is correct?
A.
They do not have a well-differentiate plant body
B.
They do not have vascular tissues
C.
They reproduce through spores
D.
They reproduce through seeds
Solution:
Ptreidophytes reproduce by producing naked embryos called spores.
The correct answer is C.
Why alternative A is wrong:
Pteridophytes have a well-differentiated plant body.
Why alternative B is wrong:
Pteridophytes have vascular tissues.
Why alternative D is wrong:
Pteridophytes do not produce seeds.
Question 38 ( 1.0 marks)
Use the following information to answer the next question.
Plant X is a member of Division
A.
Bryophyta
B.
Pteridophyta
C.
Dicotyledon
D.
Monocotyledon
Solution:
The seeds of angiosperms have one or two cotyledons in them. In the given illustration, the seed has two cotyledons. Plants with seeds having two cotyledons are known as dicots.
The correct answer is C.
Bryophytes and pteridophytes produce naked embryos called spores. They do not produce seeds. Monocots have seeds with one cotyledon.
Question 39 ( 1.0 marks)
When water is polluted by fertilizers containing nitrogen and phosphorus, the populations of which of the following organisms will increases exponentially?
A.
Phytoplankton
B.
Zooplankton
C.
Algae
D.
Fish
Solution:
Water pollution is caused when excess fertilizers containing nitrogen and phosphorus seep into the water bodies. The population of algae increases in water. This process is called eutrophication.
The correct answer is C.
The population of phytoplankton, zooplankton, and fish do not increase as a result of water getting polluted by fertilizers containing nitrogen and phosphorus.
Question 40 ( 1.0 marks)
Air in the atmosphere is responsible for
A.
occurrence of high tides
B.
the amount of rainfall on Earth
C.
revolution of the Earth around the Sun
D.
the Earth’s atmospheric temperature
Solution:
Air is a bad conductor of heat. Therefore, the presence of air in the atmosphere prevents the sudden decrease or increase in temperatures on the Earth.
The correct answer is D.
Why alternative A is wrong:
Tides occur because of the gravitational pull between the Earth and the Moon.
Why alternative B is wrong:
Rainfall depends on the water cycle.
Why alternative C is wrong:
Centripetal force keeps the Earth in its orbit and the gravitational force of the Sun makes the Earth move around it.
Question 41 ( 1.0 marks)
Use the following information to answer the next question.
What is the work done by the brakes?
A.
17187.5 J
B.
24125.0 J
C.
421848.0 J
D.
515625.5 J
Solution:
According to the third equation of motion,
u = Initial velocity = 25 m/s
s = Distance covered by the car after the brakes were applied = 30 m
 = Final velocity of the car = 0
(As the car eventually comes to rest)
Acceleration = a
Here, negative sign indicates that the acceleration is acting in the opposite direction to the motion of the car.
From Newton’s second law of motion,
Force exerted by the brakes, F
F = Mass × Acceleration
Mass of the car, m = 1350 kg
∴F = 1350 × (−10.416) = −14061.6 N
Work done, W = Force × Displacement
Force, F = −14061.6 N
Displacement, d = 30 m
∴W = −14061.6 × 30 = −421848 J
Here, negative sign indicates that the work done by the brakes is opposite to the motion of the car.
The correct answer is C.
 |
waves because their vibrations are 
to the direction of propagation of the waves.