Tamil Nadu Class 9 Science Chemistry Unit Test — Samacheer Kalvi

Class 9 Science — Chemistry Unit Test

Time: 2 Hours | Marks: 50

Section A — 1 Mark (1 × 10 = 10)

1. What are the three states of matter? 2. Define sublimation with one example. 3. Who proposed the nuclear model of the atom? 4. What is the atomic number of Carbon? 5. Define isotopes. 6. What is a solution? Give one example. 7. What is the difference between physical and chemical change? 8. What are allotropes of carbon? Name two. 9. In the Periodic Table, what does a period represent? 10. What is valency?

Section B — 3 Mark (3 × 5 = 15)

(Choose 5 of 6)

1. Describe Rutherford's gold foil experiment. What conclusions did he draw? 2. Distinguish between isotopes and isobars with two examples each. 3. What are the factors affecting the rate of evaporation? Explain any three. 4. Draw the Bohr model of the atom for Sodium (Na, atomic number 11). 5. Distinguish between saturated and unsaturated solutions. How can you convert a saturated solution to an unsaturated one? 6. What are the properties of the periods and groups in the modern Periodic Table?

Section C — 5 Mark (5 × 3 = 15)

(Choose 3 of 4)

1. Explain the evolution of atomic models from Thomson to Bohr — include key features, experiments, and limitations of each. 2. Describe the properties of the three states of matter and explain the interconversion processes (melting, boiling, condensation, freezing). 3. What are allotropes of carbon? Compare diamond and graphite in terms of structure and uses. 4. Explain the trends in the Periodic Table — along a period and down a group — for atomic size and metallic character.

Section D — Application Questions (1 × 10 = 10)

1. An element has 17 protons and 18 neutrons. Find: (a) atomic number, (b) mass number, (c) number of electrons, (d) electron configuration. (2 marks) [17; 35; 17; 2,8,7]

2. Identify the type of change (physical or chemical):

(5 × 1 = 5 marks)

• Burning of paper (Chemical)
• Melting of ice (Physical)
• Rusting of iron (Chemical)
• Boiling of water (Physical)
• Digestion of food (Chemical)

3. A solution contains 25 g of salt in 475 g of water. Find the mass percentage of the solution. (3 marks) [25/500 × 100 = 5%]

End of Chemistry Unit Test