Class IX - Science Practice Paper - 4 - Answers

Subject: Science

Class IX

Time Allowed: 3 hours

Max Marks: 80

General Instructions:

The question paper comprises four sections A, B, C and D. there are 37 questions in the question paper. All questions are compulsory.
Section A question no 1 – 20 – all questions and parts thereof are of one mark each.
Section B question no 21 – 26 are short answer type questions carrying 2 marks each.
Section C question no 27 – 34 are short answer type questions, carrying 3 marks each.
Section D question no 35 – 37 are long answer type questions carrying 5 marks each
There is no overall choice. However, internal choices have been provided in some questions.
Wherever necessary, neat and properly labelled diagrams should be drawn.

Section – A

1. Name the particles which determine the mass of an atom.

View Answer

Ans. Protons and Neutrons

There are 15 protons and 16 neutrons in the nucleus of an element. Calculate its atomic number and its atomic mass.

View Answer

Ans. Atomic number (Z) = Number of protons = 15

Atomic mass (A) = Number of protons + number of neutrons

= 15 + 16 = 31

2. Give the other name of dividing cells in plants.

View Answer

Ans. Meristematic cells (meristematic tissue)

3. Which of the following can be made into crystals?

A) A bacterium

B) An Amoeba

C) A virus

D) A sperm

View Answer

Ans. (C)

4. If the displacement of a body is zero, is it necessary that the distance covered by it is also zero?

View Answer

Ans. No. When the body comes back to the same position after travelling a distance, its displacement is zero though it has travelled some distance.

5. Why is it difficult for a fireman to hold a hose, which ejects large amount of water at a high velocity?

View Answer

Ans. Water is ejected from a hose with a large amount of force (action). Hence as per Newton’s III law there will be an equal and opposite force on the hose pipe making it difficult to hold.

6. What will be the valency of an atom with 3 protons and 4 neutrons?

View Answer

Ans. 1

Study the composition of the two nuclei of two atomic species L and M.

L = protons 20, neutrons 20

M = protons 18, neutrons 22

Give the relation between the two

View Answer

Ans. L = necleons = 20 + 20 = 40

M = nucleons = 18 + 22 = 40

Both have same atomic mass but different atomic number.

Relation between L and M: Isobars

7. How many Newtons are there in 1 kg-wt?

View Answer

Ans. 9.8 Newton

8. A 2 m high person is holding a 25 kg trunk on his head and is standing at a roadways bus-terminus. How much work is done by the person?

View Answer

Ans. No work is done as force is applied to keep the trunk on the head but there is no displace of the body. Hence work done is zero.

9. What are polyatomic ions? Give one example.

View Answer

Ans. Polyatomic ions are a group of atoms carrying charge. They are also called molecular ion

Example: Carbonate or phosphate or nitrate ion.

10. A few substances are arranged in the increasing order of ‘forces of attraction’ between their particles. Which one of the following represents a correct arrangement?

A) Water, air, wind

B) Air, sugar, oil

C) Oxygen, water, sugar

D) Salt, juice, air

View Answer

Ans. (C)

Reason: It is because the force of attraction increases in the order Gas < Liquid < Solid

11. Write the atomicity of the following molecules:

i) H₂SO₄

ii) CCl₄

View Answer

Ans. i) 7 (2 + 1 + 4)

ii) 5 (1 + 4)

12. Who discovered the living cells?

View Answer

Ans. In 1670, Anton Van Leeuwenhoek discovered the living cell.

Name the process by which unicellular freshwater organisms and most plant cells tend to gain water.

View Answer

Ans. Endosmosis. When cell is kept in hypotonic solution, it will gain water.

13. Write two functions of stomata.

View Answer

Ans. Exchange of gases and transpiration.

Name the following tissues:

i) Found in the iris of the eye

View Answer

Ans. Involuntary muscular tissue

ii) That connects two bones

View Answer

Ans. Ligament

14. Explain why is the removal of weeds necessary from the cultivated fields?

View Answer

Ans. Weeds take up nutrients and reduce the growth of the crop. Therefore their removal is necessary.

For question numbers 15, 16 and 17, two statements are given – one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

A) Both A and R are true, and R is correct explanation of the assertion

B) Both A and R are true, and R is not correct explanation of the assertion

C) A is true, but R is false

D) A is false, but R is true

15. Assertion: Inert elements show zero valency

Reason: Atoms of inert element has fully filled outermost orbit.

A) Both A and R are true, and R is correct explanation of the assertion

B) Both A and R are true, and R is not correct explanation of the assertion

C) A is true, but R is false

D) A is false, but R is true

View Answer

Ans. (A)

Reason: Noble gases have completely filled electrons in their outermost shell with eight electrons.

Thus, they cannot lose, gain or share electrons with atoms of other elements. Therefore, the valency of these gases is zero.

16. Assertion: A lamp consumes 1000J of electrical energy in 10 s. its power is 100W

Reason: Power is obtained by dividing the energy consumed by the time taken.

A) Both A and R are true, and R is correct explanation of the assertion

B) Both A and R are true, and R is not correct explanation of the assertion

C) A is true, but R is false

D) A is false, but R is true

View Answer

Ans. (C)

Reason: Power of lamp = Energy/Time

P = 1000/10 = 100 W

Assertion: SI unit of power I Joules.

Reason: One kWh is equal to 3.6 x 10⁶ J.

A) Both A and R are true, and R is correct explanation of the assertion

B) Both A and R are true, and R is not correct explanation of the assertion

C) A is true, but R is false

D) A is false, but R is true

View Answer

Ans. (C)

Reason: SI unit of power is Watt. One KWh is equal to 3.6 x 10⁶ J

17. Assertion: The only cell organelle seen in prokaryotic cell is ribosome.

Reason: A prokaryotic cell lacks membrane-bound organelles like plastids, mitochondria and endoplasmic reticulum.

A) Both A and R are true, and R is correct explanation of the assertion

B) Both A and R are true, and R is not correct explanation of the assertion

C) A is true, but R is false

D) A is false, but R is true

View Answer

Ans. (B)

Reason: A prokaryotic cell lacks membrane-bound organelles like plastids, mitochondria and endoplasmic reticulum but smaller and randomly scattered ribosomes are seen.

18. Read the following and answer any four questions from 18(i) to 18(v)

Sunil while playing football with his friends got injured suddenly. His friends took him to the hospital and the doctor told that he was suffering from a sprain and advised bed rest. Every afternoon, his friends visited him to enquire about his health.

(i) What happens during a sprain?

A) During a sprain, bone gets stressed.

B) During a sprain, the joint gets stressed.

C) During a sprain, the ligament gets stressed.

D) During a sprain, cartilage gets stressed.

View Answer

Ans. (C)

(ii) Which tissue helps in connecting bones with each other?

A) tendon helps in connecting bones with each other

B) Ligament helps in connecting bones with each other.

C) Nervous tissue mainly helps in connecting bones with each other.

D) Cartilage helps in connecting bones with each other.

View Answer

Ans. (B)

(iii) Tissue that connects muscle to bone in humans is ____________

A) Tendon

B) Ligament

C) Cartilage

D) Nervous tissue

View Answer

Ans. (A)

(iii) A person met with an accident in which two long bones of the hand were dislocated. What could be the reason?

A) Breakage of the cartilage which connects the two bones and keeps them in place.

B) Breakage of bones

C) Breakage of the ligament which connects the two bones and keeps them in place

D) Breakage of the tendons which connects the two bones and keeps them in place.

View Answer

Ans. (C)

(v) Which type of connective tissue forms supporting framework of the body?

A) Cartilage

B) Bone

C) Tendon

D) Ligament

View Answer

Ans. (B)

19. Read the following and answer any four questions from 19 (i) to 19 (v)

Study the given figure and answer the following questions:

i) What will be the work done in the above situations? State whether it will be positive, negative or zero

View Answer

Ans. In fig (i), Work done is zero.

In fig (ii) work done is positive

ii) Give reason for the same in each case

View Answer

Ans. In figure, the direction of force (F) and displacement are perpendicular to each other. There is no displacement in the direction of force so the work done is zero.

In fig (ii), the direction of force F and displacement are in the same direction. Hence, work done by the force is positive.

iii) Define one joule of work

View Answer

Ans. One joule of work is said to be done on an object when a force of one Newton displaces it by one meter along the line of action of the force.

iv) Write an expression for work in terms of force and displacement.

View Answer

Ans. W = F x d

v) In case of negative work, the angle between the force and displacement is ________

View Answer

Ans. 180⁰

20. In the following table the mass number and the atomic number of certain elements are given. Study the given data and answer any four questions from 20 (i) to 20 (v)

i) Which of them is a cation?

View Answer

Ans. B, as no of protons greater than no of electrons

ii) Which of them is an anion?

View Answer

Ans. A, as no of electrons is greater than no of protons.

iii) Which of them is a pair of isotope?

View Answer

Ans. C and E as they have same atomic number but different mass number.

iv) Which is an atom of a noble gas?

View Answer

Ans. D as it has 8 electrons in its valence shell.

v) Say true or False: Elements A and B are isobars of each other.

View Answer

Ans. False

Section – B

21. Give reasons for the following:

i) Branches of a tree move and bend freely in high wind velocity.

View Answer

Ans. Branches of a tree have collenchyma which provide flexibility

ii) It is difficult to pull out the husk of coconut.

View Answer

Ans. Husk of coconut is composed of sclerenchyma and these fibres are closely packed.

Explain how the bark of a tree is formed. How does it act as a protective tissue?

View Answer

Ans. As plants grow older; the outer protective tissue undergoes certain changes. A strip of secondary meristem replaces the epidermis of stem. Cells on the outside are cut off from this layer. This forms the several layered thick cork or back.

They also have a chemical called suberin in their wall which makes them impervious to gases and water.

22. How would you differentiate between a molecule of element and a molecule of compound? Write one example of each type.

View Answer

Ans. Molecule of element is made up of only one kind of atom.

Eg. C, Br₂, O₂

Molecule of compound contains two or more different kinds of atoms in a fixed ratio.

Eg. H₂O, CO₂

23. List any three characteristics of colloid.

View Answer

Ans. (i) It is heterogeneous mixture

(ii) Particles of colloids scatter a beam of light (Tyndall effect)

Identify colloid from the following mixtures: Muddy water, Sugar in water, Ink, Blood, Soda water

View Answer

Ans. Ink, blood

24. Differentiate between Fertilisers and Manure.

View Answer

Ans. Differences between Fertilizers and manure

S.No	Fertilizers	Manure
(i)	They are chemical in nature and these are manufactured in factories.	Manure is an organic substance that is obtained from decomposition of vegetable and animal wastes.
(ii)	Microbes are not needed for their formation	Microbes are needed to form manure since they degrade the organic substances.
(iii)	Easy to transport, store and apply to crops	It is difficult to transport, store and to utilise for crops.
(iv)	They do not restore soil texture.	They restore soil texture
(v)	They do not help in retention of water	They help in the retention of water.

25. Water sprinkler used for grass lawn begins to rotate as soon as the water is supplied. Explain the principle on which it works.

View Answer

Ans. It works on third law of motion. As the water comes out of the nozzle of the sprinkler, an equal and opposite reaction force comes into play. So the sprinkler starts rotating.

Average velocity is the total displacement covered in total time.

Section – C

27 (i) Which cell organelle would you associate with ATP production? How is this organelle able to make its own proteins?

View Answer

Ans. Mitochondria is associated with ATP production. It has own DNA and ribosomes to make proteins.

(ii) A student performed an experiment by placing the de-shelled egg in a concentrated salt solution for five minutes. What changes did he observe in the egg? Give reason for the same.

View Answer

Ans. The egg shrinks because water passes out of the egg solution, into the salt solution due to osmosis.

Describe the structure, function and location of the nervous tissue.

View Answer

Ans. The nervous tissue is made up of neurons which consists of a cell body with a nucleus and cytoplasm, from which long think hair like parts arise.

On stimulation, the nerve cells transmit the stimulus very rapidly from one place to another within the body.

Nervous tissues are located in the brain, spinal cord and nerves.

28. Atom A has a mass number 238 and atomic number 92 and atom B has mass number 235 and atomic number 92.

i) How many protons, atoms A and B have?

View Answer

Ans. Protons in atoms A and B = 92

ii) How many neutrons, atoms A and B have?

View Answer

Ans. Neutrons in atoms A and B = 146 and 143

iii) Are atoms A and B isotopes of the same element? How?

View Answer

Ans. Yes, atoms A and B are isotopes of the element since they have the same atomic number or same electronic configuration.

29. State universal law of Gravitation. Derive an expression for gravitational force between the two bodies.

View Answer

Ans. Universal law of gravitation states that the force of attraction between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Let the two bodies ‘A’ and ‘B’ be of masses ‘M’ and ‘m’ respectively, which are separately by a distance ‘r’

According to Universal law of Gravitation,

Then, F α M x m

And F α 1/r²

Combining (i) and (ii),

F = G M x m/r²

Where ‘G’ is called universal gravitation constant.

The numerical value of G = 6.67 x 10^-11 Nm² kg^-2

30. Arrange solids. Liquids and gases in increasing order of the following properties of matter.

(i) rigidity

View Answer

Ans. Gases < Liquids < Solids

(ii) diffusion

View Answer

Ans. Solids < Liquids < Gases

(iii) compressibility

View Answer

Ans. Solids < Liquids < Gases

31. Explain what is observed when a strong beam of light is focused on a colloidal solution of starch in water. Name the phenomenon.

View Answer

Ans. When a strong beam of light is passed through colloidal solution of starch, the path of light becomes visible, which scatters through the solution. This phenomenon is known as Tyndall effect.

Show the formation of chemical formulae of following compounds using their ions:

(i) Ammonium sulphate

View Answer

Ans.

(ii) Magnesium nitrate

View Answer

Ans.

(iii) Aluminium sulphide

View Answer

Ans.

32. What happens when:

(i) Methylene blue stain is added to human cheek cell.

View Answer

Ans. Because of its affinity for DNA and RNA, methylene blue will produce a darker stain leading the DNA in the nucleus to stand out so that nucleus can be clearly seen.

(ii) Rheo leaves are boiled in water and a drop of sugar is added to it.

View Answer

Ans. On boiling, all the cells of Rheo leaves become dead. On adding sugar syrup nothing will happen as liquid cannot pass through dead cell membrane.

(iii) RBCs are kept in concentrated solution.

View Answer

Ans. On placing RBCs in concentrated solution, the water will come out and the cell will shrink as the concentration of solution outside is higher than inside the cell. As a result of osmosis, water comes out of the cell to maintain equilibrium.

33. The following figure shows a wave of frequency 50 Hz. Find from graph:

(i) The amplitude

View Answer

Ans. Amplitude is maximum displacement = 3 cm

(ii) The wavelength

View Answer

Ans. Wavelength (l) = Distance between two crests

= 25 – 5 = 20 cm

= 0.2 m

(iii) The velocity of the wave

View Answer

Ans. Velocity = Frequency x wavelength

= 50 x 0.2 = 10 m/s

(i) Establish the relation between speed of sound wave, wavelength of wave and frequency of wave.

View Answer

Ans. Speed = Distance /time

v = λ/T

v = λ(1/T)

v = λV

(ii) Sound wave of frequency 512 Hz moves with a speed of 340 ms^-1 in air. What will be the speed of a sound wave of frequency 256 Hz?

View Answer

Ans. It will be same.

34 (i) Using the symbols given below make a diagrammatic representation of intercropping – Crop A- ●Crop B – ◊

Ans.

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(ii) Give two examples of crops selected for intercropping.

View Answer

Ans. Soyabean + maize, finger millet + cowpea

(iii) Mention two benefits that a farmer gets by following this cropping pattern.

View Answer

Ans. It ensures maximum utilisation of nutrients

It prevents pest and diseases from spreading to all plants.

Section – D

35 (i) Find out acceleration over each of the intervals OA, AB and BC

View Answer

Ans. Acceleration:

(OA) = 10 – 0)/5 = 2 m/s²

(AB) = 0 (uniform motion)

(BC) = (25 – 10)/2 = 5 m/s²

(ii) Calculate distance covered in last 3 seconds

View Answer

Ans. S = Area of trapezium BCEF

= ½ x (BE + CF) x EF

=1/2 x (10 + 25) x 3

= 52.5 m

(a) Draw the velocity time graph to show:

(i) the change in velocity of a freely falling body.

(ii) the change in velocity of a body thrown vertically upwards.

View Answer

Ans.

(b) Comment on the kind of motion of the body while: (i) it comes down (ii) it goes up

View Answer

Ans. (i) Motion is uniformly accelerated when it goes vertically downwards.

(ii) Motion is uniform with negative acceleration when it goes up.

36. Answer the following questions:

(i) Out of boiling and evaporation which is a surface phenomenon? Explain. In the absence of a refrigerator, butter is kept wrapped in a wet cloth during summer. Why?

View Answer

Ans. Evaporation is a surface phenomenon. Particles from the surface gain enough energy to overcome the forces of attraction present in the liquid and change into vapour state.

Due to wet cloth, the temperature is comparatively lower than room temperature.

So, butter does not melt when remain wrapped in wet clothes.

(ii) Why do ice-cream appears colder that water at the same temperature?

View Answer

Ans. Ice cream at 273 K, will take latent heat from the medium to convert itself into liquid at 273 K and then into liquid at higher temperature but in water such condition is not possible.

37. What are the differences between striated, unstriated and cardiac muscles?

View Answer

Ans.

The growth of plant occurs only in specific regions:

(i) Name the tissue which is responsible for this growth. Mention any two characteristics of the cells of this tissue.

View Answer

Ans. Meristematic tissue

Cells of this tissue are:

(i) Very active

(ii) have dense cytoplasm

(iii) have thin cellulose walls and prominent nuclei

(iv) lack vacuoles

(ii) State the different types of this tissue. Write one function of each.

View Answer

Ans. The different types of meristematic tissue are:

(i) Lateral meristem: Helps in growth and development of plant’s shoot girth.

(ii) Intercalary meristem: Helps in increasing internodes of plants like sugarcane.

(iii) Apical meristem: Helps in growth of the stem and the root.

Class IX – Science Practice Paper – 4 – Answers