Class 9 Science Test Paper with Solutions – Chapters 5 & 8

Class 9 Science Test — 60 Marks (Class 9 Science Test Paper with Solutions)

Chapter 5: Exploring Mixtures and Their Separation & Chapter 8: Journey Inside the Atom

Time: 2 Hours Maximum Marks: 60

General Instructions

1. All questions are compulsory unless a choice is given.
2. Write answers neatly and show all necessary steps.
3. Draw labelled diagrams wherever required.

Section A — Multiple Choice Questions 10 × 1 = 10 marks

1. Which of the following is a homogeneous mixture?
   a) Sand and water b) Salt solution c) Oil and water d) Soil
2. The method used to separate an insoluble solid from a liquid is:
   a) Evaporation b) Filtration c) Distillation d) Sublimation
3. Which technique is commonly used to separate different coloured dyes in ink?
   a) Filtration b) Chromatography
   c) Sedimentation d) Decantation
4. A mixture of iron filings and sand can be separated using:
   a) A magnet b) Filtration
   c) Evaporation d) Distillation
5. The negatively charged particle in an atom is the:
   a) Proton b) Neutron
   c) Electron d) Nucleus
6. The nucleus of an atom contains:
   a) Only electrons
   b) Protons and neutrons
   c) Only neutrons
   d) Protons and electrons
7. The atomic number of an element is equal to the number of:
   a) Neutrons b) Electrons + neutrons
   c) Protons d) Protons + neutrons
8. The maximum number of electrons that can be present in the first shell is:
   a) 1 b) 2 c) 8 d) 18
9. Atoms of the same element having different numbers of neutrons are called:
   a) Ions b) Isotopes
   c) Molecules d) Compounds
10. Which scientist proposed the nuclear model of the atom based on the alpha-particle scattering experiment?
    a) Dalton b) Thomson
    c) Rutherford d) Bohr

Section B — Very Short Answer Questions 5 × 2 = 10 marks

11. What is a mixture? Give one example.
12. Differentiate between a homogeneous mixture and a heterogeneous mixture.
13. What is evaporation? Give one situation where it is used to separate a mixture.
14. Name the three fundamental subatomic particles and state their charges.
15. What is meant by the atomic number and mass number of an atom?

Section C — Short Answer Questions 5 × 3 = 15 marks

16. Explain the difference between a solution, suspension and colloid. Give one example of each.
17. Describe how you would separate a mixture containing sand, salt and water. Mention the steps in the correct order.
18. Explain Rutherford’s alpha-particle scattering experiment and write two conclusions drawn from it.
19. What are isotopes? Explain with an example. Write one use of isotopes.
20. An atom has 11 protons, 12 neutrons and 11 electrons. Find:
    a) Atomic number
    b) Mass number
    c) Whether the atom is electrically neutral or charged

Section D — Long Answer Questions 3 × 5 = 15 marks

21. Explain any five methods of separation of mixtures. For each method, give one example.

OR

Explain how you would separate a mixture of iron filings, sand, common salt and water. Write the complete procedure.

22. Explain the structure of an atom according to Bohr’s model. Include:

• Nucleus, Electrons, Electron shells, Distribution of electrons in shells

Draw a neat labelled diagram of an atom.

23. Compare Thomson’s model, Rutherford’s model and Bohr’s model of the atom. Mention one important feature of each model.

Section E — Application & Competency-Based Questions 2 × 5 = 10 marks

24. A student is given a mixture containing water, sand, salt and small iron pieces.

Answer the following:

a) Which method should be used first to remove the iron pieces? (1)
b) How can sand be separated from the remaining mixture? (1)
c) How can salt be obtained from the salt solution? (1)
d) Name the property on which filtration is based. (1)
e) Why can salt not be separated from water by ordinary filtration? (1)

25. Read the information and answer the questions:

An atom X has atomic number 17 and mass number 35.

1. Find the number of protons. (1)
   b) Find the number of electrons in a neutral atom. (1)
   c) Find the number of neutrons. (1)
   d) Write its electronic configuration. (1)
   e) Is it likely to gain or lose electrons to attain a stable configuration? (1)

Solution

Class 9 Science Test — Complete Solutions

Chapters 5: Exploring Mixtures and Their Separation & Chapter 8: Journey Inside the Atom
Total: 60 Marks

Section A — MCQs

1. b) Salt solution
2. b) Filtration
3. b) Chromatography
4. a) A magnet
5. c) Electron
6. b) Protons and neutrons
7. c) Protons
8. b) 2
9. b) Isotopes
10. c) Rutherford

Section B — Very Short Answers

11. What is a mixture? Give one example.

A mixture is a substance formed when two or more substances are combined physically in any proportion, without undergoing a chemical change.

Example: Salt and water.

12. Difference between homogeneous and heterogeneous mixtures

13. What is evaporation?

Evaporation is the process in which a liquid changes into vapour from its surface.

Example: Salt is obtained from seawater by evaporation.

14. Name the three fundamental subatomic particles and their charges.

• Proton: Positive (+1)
• Electron: Negative (−1)
• Neutron: No charge (0)

15. Atomic number and mass number

• Atomic number (Z): Number of protons present in the nucleus of an atom.
• Mass number (A): Total number of protons and neutrons in the nucleus.

Mass number = Protons + Neutrons

Section C — Short Answers

16. Solution, suspension and colloid

17. Separate sand, salt and water

The mixture contains sand + salt + water.

Step 1: Filtration
Pass the mixture through filter paper. Sand remains as the residue while salt solution passes through.

Step 2: Evaporation
Heat the salt solution. Water evaporates and salt is left behind.

Thus, sand and salt can be separated from the mixture.

18. Rutherford’s alpha-particle scattering experiment

Rutherford directed a beam of alpha particles at a very thin gold foil and observed where the particles went after striking the foil.

Observations:

1. Most alpha particles passed straight through the foil.
2. Some particles were deflected through small angles.
3. A very small number were deflected backward.

Conclusions:

1. Most of the atom is empty space.
2. Almost all the mass and positive charge of an atom is concentrated in a very small, dense nucleus.
3. Electrons occupy the space around the nucleus.

19. What are isotopes?

Isotopes are atoms of the same element having the same atomic number but different mass numbers.

Example: Carbon has isotopes:

• Carbon-12
• Carbon-14

Both have 6 protons, but they have different numbers of neutrons.

One use: Carbon-14 is used for determining the age of ancient fossils.

20. Atom with 11 protons, 12 neutrons and 11 electrons

Given:

• Protons = 11
• Neutrons = 12
• Electrons = 11

a) Atomic number

Atomic number = number of protons

Atomic number = 11

b) Mass number

Mass number = protons + neutrons

Mass number = 11 + 12 = 23

c) Charge

Protons = electrons = 11

Therefore, the atom has no net charge and is electrically neutral.

Section D — Long Answers

21. Five methods of separation of mixtures

1. Filtration:
Used to separate an insoluble solid from a liquid.
Example: Sand from water.

2. Evaporation:
Used to obtain a dissolved solid from a solution.
Example: Salt from seawater.

3. Magnetic separation:
Used when one component of a mixture is attracted by a magnet.
Example: Iron filings from sand.

4. Sedimentation and decantation:
A heavier insoluble solid settles at the bottom and the clear liquid can be carefully poured off.
Example: Separating mud from water.

5. Chromatography:
Used to separate components of a mixture based on their different movement through a medium.
Example: Separating different dyes present in ink.

OR

For iron filings + sand + salt + water:

1. Use a magnet to remove iron filings.
2. Use filtration to separate sand from the salt solution.
3. Use evaporation to obtain salt from the salt solution.

22. Bohr’s model of the atom

According to Bohr’s model:

1. An atom has a small, positively charged nucleus at its centre.
2. The nucleus contains protons and neutrons.
3. Electrons revolve around the nucleus in fixed paths called shells or energy levels.
4. These shells are represented as K, L, M, N…
5. Electrons occupy shells according to their energy and capacity.

For the first few shells, the maximum capacity is given by 2n², where n is the shell number.

For example:

• K shell → maximum 2 electrons
• L shell → maximum 8 electrons
• M shell → maximum 18 electrons

Example: Sodium (Na), atomic number 11

Electronic configuration = 2, 8, 1

23. Thomson, Rutherford and Bohr models

Section E — Application & Competency

24. Mixture of water, sand, salt and iron pieces

a) First use a magnet to remove the iron pieces.

b) Use filtration to separate sand from the salt solution.

c) Use evaporation to obtain salt from the salt solution.

d) Filtration is based on the difference in particle size and the insolubility of the solid in the liquid.

e) Salt cannot be separated by ordinary filtration because salt is dissolved in water and its particles are too small to be retained by ordinary filter paper.

25. Atom X

Given:

Atomic number = 17
Mass number = 35

a) Number of protons

Atomic number = number of protons.

Protons = 17

b) Number of electrons

For a neutral atom:

Electrons = Protons = 17

c) Number of neutrons

Neutrons = Mass number − Atomic number

= 35 − 17 = 18

Therefore, neutrons = 18.

d) Electronic configuration

There are 17 electrons.

Distribution:

K = 2, L = 8, M = 7

So the electronic configuration is:

2, 8, 7

e) Will it gain or lose electrons?

The outermost shell contains 7 electrons. It needs 1 more electron to achieve a stable octet.

Therefore, it will gain 1 electron.

Answer: X tends to gain one electron.