Chapter Overview
3
States of Matter
273K
Melting Point of Ice
373K
Boiling Point of Water
5
Panch Tatva Elements
What You'll Learn
Physical Nature of Matter
Understanding that matter is made up of particles and their characteristics.
States of Matter
Exploring solid, liquid, and gas states and their properties.
Change of State
Learning how matter changes states with temperature and pressure.
Evaporation
Factors affecting evaporation and its cooling effect.
Historical Context
This chapter introduces the concept of matter based on ancient classifications like Panch Tatva (air, earth, fire, sky, water) by Indian philosophers and similar ideas by Greek philosophers. Modern science classifies matter into solids, liquids, and gases based on physical properties.
Key Highlights
Matter occupies space and has mass. Particles are very small, continuously moving, with spaces between them, and attract each other. States change with temperature (melting, boiling) and pressure. Evaporation causes cooling and depends on surface area, temperature, humidity, and wind speed.
Comprehensive Chapter Summary
1. Introduction to Matter
Everything in the universe is matter, which occupies space and has mass. Ancient Indian and Greek philosophers classified matter into five elements: air, earth, fire, sky, water. Modern classification is based on physical and chemical properties.
2. Physical Nature of Matter
Matter is Made Up of Particles
Matter consists of particles, as shown by dissolving salt in water without changing water level. Particles spread throughout the water.
How Small Are These Particles?
Particles are tiny; a few crystals of potassium permanganate color a large volume of water through repeated dilution.
3. Characteristics of Particles of Matter
Particles Have Space Between Them
Sugar or salt particles fit into spaces between water particles when dissolved.
Particles Are Continuously Moving
Incense smell spreads, ink diffuses in water, showing particle motion increases with temperature.
Particles Attract Each Other
Force of attraction holds particles together, varying by matter type, as in breaking chains or substances.
4. States of Matter
Solid, Liquid, Gas
Solids have definite shape and volume; liquids have fixed volume but no shape; gases are compressible with no fixed shape or volume.
5. Change of State
Effect of Temperature and Pressure
Heating causes melting and boiling; pressure compresses gases to liquids.
Latent Heat
Latent heat of fusion and vaporization absorbed during state changes without temperature rise.
6. Evaporation
Evaporation is surface phenomenon below boiling point. Factors: surface area, temperature, humidity, wind speed. Causes cooling by absorbing energy.
Questions and Answers from Chapter
Short Questions
Q1. Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume.
Answer: Chair, air, almonds, cold, lemon water.
Q2. Give reasons for the following observation: The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close.
Answer: Particles move faster in hot food.
Q3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Answer: Particles have space between them.
Q4. What are the characteristics of the particles of matter?
Answer: Space, motion, attraction.
Q5. Give reasons (a) A gas fills completely the vessel in which it is kept.
Answer: Particles move freely.
Q6. Give reasons (b) A gas exerts pressure on the walls of the container.
Answer: Particles hit walls.
Q7. Give reasons (c) A wooden table should be called a solid.
Answer: Definite shape and volume.
Q8. Give reasons (d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.
Answer: More space in air.
Q9. Convert the following temperature to celsius scale: a. 300 K
Answer: 27°C.
Q10. Convert the following temperature to celsius scale: b. 573 K
Answer: 300°C.
Q11. What is the physical state of water at: a. 250°C
Answer: Gas.
Q12. What is the physical state of water at: b. 100°C
Answer: Liquid and gas.
Q13. For any substance, why does the temperature remain constant during the change of state?
Answer: Latent heat absorption.
Q14. Suggest a method to liquefy atmospheric gases.
Answer: Increase pressure, decrease temperature.
Q15. Why does a desert cooler cool better on a hot dry day?
Answer: Low humidity.
Medium Questions
Q1. The mass per unit volume of a substance is called density. (density = mass/volume). Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton and iron.
Answer: Air, exhaust from chimneys, cotton, water, honey, chalk, iron. This order is based on particle closeness and mass per volume in each substance. (3 marks)
Q2. (a) Tabulate the differences in the characteristics of states of matter.
Answer: Solids: rigid, incompressible; Liquids: fluid, slightly compressible; Gases: highly compressible, no shape. (3 marks)
Q3. (b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
Answer: Rigidity in solids due to strong attraction; gases fill containers due to free movement. (3 marks)
Q4. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Answer: Ice has lower density due to open structure from hydrogen bonding. (3 marks)
Q5. How does the water kept in an earthen pot (matka) become cool during summer?
Answer: Evaporation through pores absorbs heat, cooling water. (3 marks)
Q6. Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Answer: Evaporation absorbs heat from palm. (3 marks)
Q7. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Answer: Larger surface area increases evaporation rate. (3 marks)
Q8. What type of clothes should we wear in summer?
Answer: Cotton clothes absorb sweat for evaporation. (3 marks)
Q9. Convert the following temperatures to the celsius scale. (a) 293 K (b) 470 K
Answer: (a) 20°C (b) 197°C. Subtract 273 from Kelvin. (3 marks)
Q10. Convert the following temperatures to the kelvin scale. (a) 25°C (b) 373°C
Answer: (a) 298K (b) 646K. Add 273 to Celsius. (3 marks)
Q11. Give reason for the following observations. (a) Naphthalene balls disappear with time without leaving any solid.
Answer: Sublimation turns solid to gas directly. (3 marks)
Q12. Give reason for the following observations. (b) We can get the smell of perfume sitting several metres away.
Answer: Diffusion of gas particles. (3 marks)
Q13. Arrange the following substances in increasing order of forces of attraction between the particles— water, sugar, oxygen.
Answer: Oxygen, water, sugar. Based on state. (3 marks)
Q14. What is the physical state of water at— (a) 25°C (b) 0°C (c) 100°C ?
Answer: (a) Liquid (b) Solid/Liquid (c) Liquid/Gas. (3 marks)
Q15. Give two reasons to justify— (a) water at room temperature is a liquid.
Answer: No fixed shape, flows easily. (3 marks)
Long Questions
Q1. Give two reasons to justify— (b) an iron almirah is a solid at room temperature.
Answer: Definite shape and volume, rigid due to strong particle attraction. Iron almirah maintains its shape under force and does not flow, characteristic of solids where particles are closely packed with minimal movement. This is because the melting point of iron is much higher than room temperature.
Q2. Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer: Ice absorbs latent heat of fusion to melt, cooling more effectively. At 273K, ice is solid and requires additional energy (latent heat) to change to liquid without temperature rise, whereas water at 273K does not absorb this extra heat, making ice better for cooling.
Q3. What produces more severe burns, boiling water or steam?
Answer: Steam, due to latent heat of vaporization. Steam at 373K has absorbed extra energy to become gas, releasing more heat upon condensation than boiling water, causing severe burns.
Q4. Name A,B,C,D,E and F in the following diagram showing change in its state
Answer: A: Fusion, B: Vaporization, C: Condensation, D: Solidification, E: Sublimation, F: Deposition. These represent state changes: solid to liquid (fusion), liquid to gas (vaporization), and direct solid-gas transitions.
Q5. Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume.
Answer: Matter: Chair, air, almonds, cold, lemon water. These have mass and occupy space. Non-matter like love, hate, thought are emotions or sensations without physical properties.
Q6. Give reasons for the following observation: The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close.
Answer: Hot food particles have higher kinetic energy, diffusing faster. In cold food, slower movement limits smell spread, requiring proximity.
Q7. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Answer: Particles in liquid have space and weak attraction, allowing movement. Water's fluidity enables the diver to pass through.
Q8. What are the characteristics of the particles of matter?
Answer: Particles have space between them, are continuously moving, and attract each other. These explain diffusion, kinetic energy, and state properties.
Q9. Give reasons (a) A gas fills completely the vessel in which it is kept.
Answer: Gas particles move freely at high speed, filling all space. Weak attraction allows expansion to vessel volume.
Q10. Give reasons (b) A gas exerts pressure on the walls of the container.
Answer: Random high-speed collisions of particles with walls exert force per unit area, creating pressure.
Q11. Give reasons (c) A wooden table should be called a solid.
Answer: Fixed shape and volume, rigid due to strong particle attraction and minimal space between particles.
Q12. Give reasons (d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.
Answer: Air has large spaces between particles; wood has tightly packed particles with strong attraction, requiring force to separate.
Q13. Convert the following temperature to celsius scale: a. 300 K b. 573 K
Answer: a. 27°C b. 300°C. Conversion formula: °C = K - 273. Explanation of absolute zero and scale difference.
Q14. What is the physical state of water at: a. 250°C b. 100°C ?
Answer: a. Gas (above boiling point). b. Liquid and gas (at boiling point). Detailed on phase transitions.
Q15. For any substance, why does the temperature remain constant during the change of state?
Answer: Energy absorbed as latent heat overcomes attraction without raising temperature. Explanation with melting/boiling examples.
