The Physical Nature of Matter – Long Answer Questions
Medium Level (Application & Explanation)
Q1. What is matter? Explain why even air is considered matter with examples.
Answer:
- Matter is anything that has mass and occupies space.
- Air is also matter, even if we cannot see it.
- Air fills a balloon and makes it expand. So it takes up space.
- A filled football feels heavier than an empty one. So air has mass.
- Air can be compressed in a syringe. That shows it occupies space.
- Thus, air fits the idea of matter as it has mass and volume.
Q2. Compare the properties of solids, liquids, and gases using particle theory.
Answer:
- In solids, particles are tightly packed and vibrate in place. Shape and volume are fixed.
- In liquids, particles are close but can slide past each other. Volume is fixed, shape is not.
- In gases, particles are far apart and move freely. Shape and volume are not fixed.
- A rock stays in one shape. That shows solid behavior.
- Water takes the shape of a cup but keeps its volume.
- Air spreads out to fill any space. That shows gas behavior.
Q3. Explain physical properties with examples and show how they help identify substances.
Answer:
- Physical properties can be observed without making a new substance.
- Examples: color, density, melting point, and boiling point.
- A lemon is yellow. That is a physical property.
- A rock is more dense than a feather. So it sinks.
- Water boils at about 100°C at normal pressure.
- These properties help us identify and compare materials safely.
Q4. Describe how ice changes to water and then to steam using particle motion and energy.
Answer:
- When ice is heated, particles gain energy.
- They vibrate faster and move apart. The solid becomes a liquid.
- This is melting. The composition stays the same: it is still water.
- On more heating, the liquid reaches its boiling point.
- Particles break free and become gas (steam).
- This is a physical change because no new substance forms.
Q5. Classify water, iron, and air at room temperature. Give reasons based on properties.
Answer:
- Water is a liquid at room temperature. It has a fixed volume but no fixed shape.
- Iron is a solid at room temperature. It has a fixed shape and volume.
- Air is a gas. It has no fixed shape or volume and fills its container.
- The particle spacing explains this: close in solids, less close in liquids, far apart in gases.
- The movement explains behavior: vibration, sliding, free motion.
- Thus, their state matches their observable properties.
High Complexity (Analysis & Scenario-Based)
Q6. A student pushes the plunger of a syringe filled with air and the plunger moves back when released. Explain this using properties of gases.
Answer:
- Air is a gas, so its particles are far apart.
- When pushed, the particles are forced closer, so the gas is compressed.
- The particles hit the walls more often. This increases pressure.
- When the push stops, the compressed gas expands again.
- The plunger moves back because the gas tries to fill more space.
- This shows gases have no fixed volume and are compressible.
Q7. A closed box has some ice. The room warms up. Describe all changes inside the box and justify if they are physical or chemical.
Answer:
- The ice absorbs heat and melts into water.
- If warming continues, water may evaporate to form water vapor.
- All changes are physical because the substance remains H2O.
- The mass remains the same in a closed box. Nothing is added or lost.
- Only the state changes: solid to liquid to gas.
- No new substance forms, so there is no chemical change.
Q8. Decide which changes are physical or chemical: burning wood, cutting paper, rusting iron, boiling water, dissolving sugar. Explain your reasons.
Answer:
- Burning wood is a chemical change. New substances like ash and gases form.
- Cutting paper is a physical change. Only size and shape change.
- Rusting iron is a chemical change. It forms iron oxide with oxygen.
- Boiling water is a physical change. Liquid water becomes water vapor.
- Dissolving sugar is a physical change. No new substance forms; sugar can be recovered.
- In chemical changes, new properties appear. In physical changes, composition stays the same.
Q9. Perfume is sprayed in one corner of a room and its smell spreads everywhere. Analyze this event using particle theory.
Answer:
- Perfume releases tiny molecules into the air.
- These particles move randomly and mix with air particles.
- They diffuse from a high concentration area to low concentration areas.
- This happens faster in gases because particles are far apart and move quickly.
- No new substance forms. It is a physical process.
- The spread proves that gases have free-moving particles and no fixed volume.
Q10. You get two clear, colorless liquids. Plan simple tests using physical and chemical properties to tell them apart.
Answer:
- First, observe physical properties: look at color and odor.
- Measure boiling point by gentle heating. Different liquids boil at different temperatures.
- Check density by comparing mass of equal volumes.
- Test evaporation rate at the same conditions. Faster evaporation suggests weaker forces.
- If safe and supervised, check flammability as a chemical property.
- Use these results to identify or distinguish the liquids without guessing.