Practice Paper – TERM II (2021 – 2022)
Class – IX
Science (086)
Time: 2 hours Maximum Marks: 40
General Instructions:
i) All questions are compulsory.
ii) The question paper has three sections and 15 questions. All questions are compulsory.
iii) Section–A has 7 questions of 2 marks each;
iv) Section–B has 6 questions of 3 marks each; and
v) Section–C has 2 case based questions of 4 marks each.
vi) Internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
SECTION – A
1. Sum of the total number of protons and neutrons present in the nucleus of an atom is the mass
number of an atom while, total number of protons present in the nucleus of an atom is its atomic
number.
The table below shows the mass number and the atomic number of certain elements named C, D and E.
Study the given data and answer the following questions:
| Elements | Mass No | Atomic No. |
| C | 14 | 7 |
| D | 40 | 18 |
| E | 40 | 20 |
(a) Which element is a noble gas?
The atomic number of element D is 18. So, its electronic configuration will be 2, 8, 8. The outermost shell is complete, so, it is a noble gas.
(b) Which two elements are isobars?
The elements having different atomic numbers but same mass numbers are called isobars. Element D and E both have same mass number i.e., 40 but different atomic number.
2. Zinc ion and phosphate ion together constitute compound “A”.
(a) Write the chemical formula for compound “A”.
(b) Calculate the ratio by mass of atoms present in a molecule of carbon dioxide. [Given: C = 12, O=16]
Atoms of carbon = 1
Mass of carbon = 12u
Atoms of oxygen = 2
Mass of oxygen = 2 x 16 = 32u
Thus, the ratio by mass of constituting elements in carbon dioxide is mass of carbon to the mass of oxygen atoms:
12 : 32
3 : 8
3. An atom of an element has three electrons in its 3rd orbit, which is the outermost shell. Write:
(a) (i) the electronic configuration (ii) atomic number
(i) Electronic configuration: 2, 8, 3
(ii) Atomic number: 13
(b) (i) number of protons (ii) valency
(i) Number of protons: 13
(ii) Valency: 3
4. During a health survey in a locality, it was found that some children fall ill more frequently than others living in the same locality.
(a) Is this a sign of good immune system? Explain.
No, it is not a sign of good immune system. Only some children fall ill means they have less resistance to diseases which is due to poor immune system.
(b) Is this a sign of good personal hygiene? Justify your statement.
No, personal hygiene is important to develop resistance against diseases. If the children are falling ill frequently, it means that they might be neglecting health and hygiene.
5. A person suffering from disease ‘X’ cannot fight even minor infections as it damages the immune system. It is mainly transmitted through sexual contacts with infected person. Identify the disease and state its causative agent.
Name of the disease: Acquired immune-deficiency syndrome (AIDS)
Causative agent: Human immune-deficiency virus (HIV)
OR
Study the picture and answer the following questions:
(a) Identify the mode of transmission of the disease in the above picture.
Mode of transmission – Air
(b) Which of the following diseases could be spread by this mode of transmission: Common cold/cholera?
Through air – Common cold or cough may occur as these are communicable diseases which spread through air.
6. Students of class IX visited a thermal power station as a part of their project. They came to know about how the conversion of energy takes place. Teacher has asked them to find the answers for conversion of energy in following cases:
(a) When coal is burnt.
Chemical energy is converted to heat energy.
(b) In a thermal power plant.
Chemical energy of fuel is converted to electrical energy.
OR
The physical quantity ‘X’ is defined as rate of doing work.
(a) Identify the quantity. State its SI unit.
Power is the rate of doing work. Hence the quantity “X” is power. Its SI unit is Watt.
(b) An electric bulb is rated 15 watts. What does it mean?
If the power of an electric bulb is 15 W, it consumes 15 joules per second.
7. Force is the push or pull upon an object which results due to its interaction with another object. This
force is directly proportional to the mass of the object on which it acts. Depending on these facts, teacher has asked Rajat to explain what will happen to the force between two objects A and B if:
(a) The mass of one object is doubled?
Force due to gravitational pull, F = Gm1m2/d2
As force is directly proportional to masses and inversely proportional to the square of distance between them, then
(a) If m1= 2m, then F becomes twice
(b) The distance between the objects is tripled? Help Rajat to find the answers
(b) If d = 3d1, then F becomes one-ninth
OR
The given table shows value of ‘g’ at equator and at poles. It is seen that it differs at the equator and on this difference.
On earth, value of g is maximum at poles and minimum at the equator.
At poles, radius of earth is less so the value of g is more than on equator, at equator radius of earth is more so, value of g is less. It is because, g ∝ 1/(R2)
SECTION B
8. Rahul took 5 moles of carbon atoms in a container and Sohan also took 5 moles of sodium atoms in
another container of same weight.
(a) Whose container is heavier?
Sohan’s container is heavier.
Explanation: Mass of container containing 5 moles of C atoms = 5 x 12 = 60 g
Mass of container containing 5 moles of Na atom = 5 x 23 = 115 g
Hence, container containing 5 moles of sodium is heavier.
(b) Both containers have same number of atoms. Explain by calculations.
Yes, it is correct. Both containers have same number of atoms since they contain same number of moles of each carbon and sodium.
No of moles of Sohan = 5 mol
No of atoms = 5 x 6.023 x 1023
= 30.115 x 1023 atoms
No of moles of Rohan = 5 mol
No of atoms = 5 x 6.023 x 1023
= 30.115 x 1023 atoms
(c) Which term is used to refer the exact number of atoms present in 12 gm of Carbon-12?
The exact number of atoms present in 12 gm of Carbon-12 is called Avogadro’s constant.
9. Show the formation of chemical formulae of the following compounds using their ions:
(a) (i) Ammonium sulphate (ii) Magnesium nitrate
(b) Interpret the number of moles of oxygen atoms in PO43-
Each mole of phosphate ion possesses 4 moles of oxygen atoms as represented by the formula.
OR
(a) Which postulate of Dalton’s atomic theory is the basis of law of conservation of mass?
Atoms can neither be created nor destroyed.
(b) Write the name of compounds represented by the following formulae:
(a) KNO3 – Potassium nitrate
(b) Al2(SO4)3 – Aluminium sulphate
(c) CCl4 – Carbon tetrachloride
(d) H2S – Hydrogen sulphide
10. Atomic number and mass number of an element are 18 and 40 respectively. Identify the
element and write the number of electrons and neutrons present in its atom. Show the
schematic atomic structure of the atom.
Name of element: Argon
Number of electrons = 18
Number of neutrons = 22
Structure: 2, 8, 8
11.Composition of the nuclei of two atoms ‘X’ and ‘Y’ are given below:
| X | Y | |
| Protons | 4 | 4 |
| Neutrons | 4 | 6 |
(a) Give the mass number of X and Y. Mention the relationship between the two atoms.
Mass number i.e., Atomic mass of element X = Number of protons + Number of neutrons = 4 + 4 = 8 u
Mass number i.e., Atomic mass of element Y = Number of protons + Number of neutrons = 4 + 6 = 10 u
Relationship between X and Y: Isotope
The atomic number of both the elements is same, but their atomic masses are different.
(b) Write the formula for calculating the maximum number of electrons in an orbit.
The formula for calculating the maximum number of electrons in an orbit is 2n2
12. State the law of conservation of energy. With the help of an example explain the law of conservation
of energy.
Energy can neither be created nor destroyed but it can be transformed from one form to the another.
Explanation of law of conservation of energy:
Let us take the example of simple pendulum. We draw a pendulum bob to one side and allow it to oscillate.
The pendulum bob has P.E. at the extreme positions. Then, it is converted to K.E. at the mean position and so on.
It comes to rest due to air resistance and friction with the hook.
Energy is lost in overcoming friction and air resistance. But total energy remains constant.
OR
An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the total work done against the force of gravity and by the force of gravity on the object? Explain with proper mathematical expressions.
Work done =mgh
Difference in height of initial and final position is zero
Therefore, Work done = mg (h2 – h1)
= mg (0) = 0 J
13 (a)Differentiate between mass and weight.
Mass is the matter content of a body, while weight is the force with which the body is attracted by the earth.
Mass is constant at all places because it is a scaler quantity
Weight keeps on changing from place to place because it is a vector quantity.
(b) The weight of a body at a height equal to be radius of the earth is ‘N’. What will be its weight at a height equal to three times the radius of the earth?
By universal law of gravitation,
F = GMm/d2
⸫ when d = 3d
Then, F = G x Mm/(3d)2 = GMm/9d2 =F/9
SECTION C
14. Read the passage and answer the following questions.
We know that food is necessary for the growth and development of the body. It provides the necessary
components such as proteins, carbohydrates and fats which are required for proper functioning of the
body. Justify the following statements:
(a) “Availability of proper and sufficient food would prevent from infectious diseases”.
Availability of proper and sufficient food is one of the measure to prevent the occurrence of the infectious diseases. As the infectious diseases also spread through the food we eat; thus, if we obtain healthy and nutritious food, free of germs causing diseases, it would definitely prevent us from catching the infection.
(b) Balanced diet is necessary for maintaining healthy body.
Yes, balanced diet provides raw materials and energy in appropriate amount in the form of protein, carbohydrates, fats, minerals, etc., which, in turn, are essential for the proper growth and functioning of the healthy body.
(c) Health of an organism depends upon the surrounding environmental conditions.
Yes, health is a state of being well enough to function well physically, mentally and socially, and these conditions depend upon the surrounding environmental conditions, e.g., if there is an unhygienic condition in the surrounding area, it is likely we might get infected or diseased.
OR
Our surrounding areas should be free of stagnant water.
Yes, this is so because many water-borne disease and insect vectors flourish in stagnant water which causes in human beings.
15. Since, work is done when a force acting on a body produces displacement in it.
Work done = Force × Displacement in the direction of force. If four men lift a 250 kg box to a height of
1 m and hold it without raising or lowering it.
(a) How much work do they do in just holding it?
Work done will be zero because the box does not move. So, the displacement is zero that’s why work done is zero.
(b) Why do they get tired while holding it?
In holding the box, men are applying a force which is opposite and equal to the gravitational force acting on the box. While applying the force, muscular effort is involved, So, they feel tired.
(c) How much work is done by the men in lifting the box?
Given, Mass, m = 250 kg
Height, h = 1 m
Acceleration due to gravity, g = 10 m/s2
Work done by the man in lifting the box
= Potential energy of box
W = mgh
On putting values,
W = 250 x 1 x 10 = 2500 J
OR
Define the work done by a constant force. Write its SI unit and define this unit.
Work is said to be done when a force acts on an object and the object covers some distance. Its SI unit is Joule. Joule is equal to the work done by a force of one newton acting through one meter.