Matter in Our Surroundings — Previous Year Questions (Class 9 Science)
Matter is anything that occupies space and has mass. Understand the properties of solids, liquids, and gases, and the forces between particles.
TL;DR: Matter is anything that occupies space and has mass. Understand the properties of solids, liquids, and gases, and the forces between particles.
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Matter is anything that occupies space and has mass. Understand the properties of solids, liquids, and gases, and the forces between particles.
Matter in Our Surroundings — Previous Year Questions with Solutions
Q (2023, 3 marks): Define matter and list its characteristic properties.
Answer: Matter is anything that occupies space and has mass.
Characteristic properties of matter:
1. It occupies space (has volume)
2. It has mass
3. It is made of particles
4. Particles have spaces between them
5. Particles are in constant motion
6. Particles attract each other
These properties explain the behavior of solids, liquids, and gases
Q (2022, 3 marks): Explain why gases are highly compressible whereas solids are not.
Answer: Gases are highly compressible because:
1. In gases, particles are far apart with large spaces between them
2. Intermolecular forces are very weak
3. Particles have high kinetic energy and move freely
4. When pressure is applied, particles move closer together, reducing spaces
Solids are not compressible because:
1. Particles are tightly packed with little space between them
2. Intermolecular forces are very strong
3. Particles are in fixed positions
4. Applying pressure cannot reduce spaces further
Q (2023, 2 marks): A 20 g sample of iron (solid) has a density of 7.9 g/cm³. Calculate its volume.
Answer: Using formula: Density = Mass / Volume
Volume = Mass / Density
Volume = 20 g / 7.9 g/cm³
Volume ≈ 2.53 cm³
Q (2021, 2 marks): Why do gases fill the entire volume of the container in which they are kept?
Answer: Gases fill the entire volume because:
1. Gas particles are in continuous rapid motion
2. Intermolecular forces are negligible
3. Particles move in all directions randomly
4. They spread throughout the available space uniformly
5. There are no fixed boundaries, so gas expands to fill the container
Q (2022, 3 marks): Compare the melting point and boiling point of ice and water. Explain the significance.
Answer: Melting point of ice = 0°C (transition from solid to liquid)
Boiling point of water = 100°C (transition from liquid to gas)
Significance:
1. Melting point is the temperature at which solid becomes liquid with applied heat
2. Boiling point is the temperature at which liquid becomes gas
3. These are constant for pure substances at atmospheric pressure
4. They indicate the strength of intermolecular forces
5. Different substances have different melting and boiling points
For water: MP = 0°C, BP = 100°C (at 1 atm pressure)
Q (2023, 3 marks): Explain the phenomenon of sublimation with an example. Give one real-life application.
Answer: Sublimation is the direct conversion of a solid into gas without passing through the liquid state.
Example: Dry ice (solid CO2) sublimes at -78.5°C, directly forming CO2 gas.
Other examples: Naphthalene, mothballs, iodine crystals
Real-life applications:
1. Freeze drying of food and medicines (preserves nutrients and structure)
2. Dry cleaning processes
3. Production of purified iodine crystals
4. Preservation of biological samples
The reverse process (gas to solid) is called deposition
Frequently Asked Questions
What is the kinetic molecular theory and its main postulates?
KMT explains the behavior of matter: (1) Matter consists of tiny particles in constant motion, (2) Particles have kinetic energy, (3) Collisions between particles are elastic, (4) The average kinetic energy is proportional to absolute temperature. This theory explains properties of solids, liquids, and gases.
How is density different from mass? Why is it important?
Mass is the amount of matter (in grams/kg), while density is mass per unit volume (g/cm³). Density is important for identifying substances, determining if objects float/sink, and comparing materials with different sizes.
More Class 9 Science PYQs
- Chemical Reactions and Equations
- Light (Reflection and Refraction)
- Electricity
- Acids, Bases and Salts
- Metals and Non-metals
- Life Processes
🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →