Chapter Overview
3
States of Matter
9
Activities
Ancient
Idea of Parmanu
0°C
Ice Melting Point
What You'll Learn
Composition of Matter
Understanding that matter is made of tiny particles and exploring through activities like breaking chalk and dissolving sugar.
States of Matter
Exploring solids, liquids, and gases based on interparticle attractions and spacing.
Interparticle Spacing
Learning how spacing differs in states and affects properties like compressibility.
Particle Movement
Observing how particles move in different states through experiments with potassium permanganate and incense.
Historical Context
This chapter explores the particulate nature of matter, drawing from ancient Indian philosopher Acharya Kanad's idea of 'Parmanu' (atom) as indivisible particles. It uses activities to demonstrate that matter consists of tiny particles held by attractions, explaining states like solid, liquid, and gas.
Key Highlights
Matter is composed of particles with interparticle spaces and attractions. Solids have strong attractions and minimal spacing, liquids have weaker ones, and gases have negligible attractions with maximum spacing. Activities illustrate melting, boiling, dissolution, and diffusion.
Comprehensive Chapter Summary
1. Introduction and Probing Questions
The chapter opens with an illustration of children on a riverbank collecting pebbles and pondering questions like why stones or sand can be piled but not water, why water takes the shape of folded hands but loses it when released, how invisible air adds weight to balloons, and if today's air is the same as thousands of years ago. It encourages sharing questions. The text explains that pebbles, stones, and sand come from eroded rocks in mountains, carried by rivers and broken further into finer grains. It questions if these grains are the smallest units or can be broken down more.
2. What Is Matter Composed of?
Activity 7.1: Let us explore - Breaking Chalk
Take a stick of chalk (Fig. 7.1a) and break it into two pieces (Fig. 7.1b). Continue breaking until difficult by hand. Grind small pieces with mortar and pestle (Fig. 7.1c). Observe fine powder with magnifying glass (Fig. 7.1d). Each grain is still chalk. Grinding is a physical change; substance remains the same, only size reduces. Imagining further grinding reaches stage where particles can't be broken - these are constituent particles, basic building blocks.
Activity 7.2: Let us perform - Dissolving Sugar
Fill glass tumbler with water. Add two teaspoons sugar. Taste top layer without stirring - not sweet. Stir until dissolved (Fig. 7.2). Taste top layer - sweet. Sugar present but invisible, detected by taste. Sugar breaks into constituent particles occupying interparticle spaces in water. Particles too small to see.
Key Idea and Heritage
Activities show matter composed of extremely small particles, not visible even under ordinary microscope. Chalk and sugar break into constituent particles. Interparticle spaces exist, as sugar particles fit between water particles. But how are particles held to form solids? Our scientific heritage: Acharya Kanad proposed Parmanu as tiny, indivisible eternal particles in Vaisheshika Sutras.
3. What Decides Different States of Matter?
Constituent particles held by attractive interparticle forces. Strength depends on nature and distance; increases with closeness. Strength decides physical state.
7.2.1 Solid State
Activity 7.3: Collect solids like iron nail, rock salt, stone, wood, key, aluminium (Fig. 7.3). Observe shapes, sizes; hammer them. All have definite shape, volume due to tightly packed particles, strong attractions, fixed positions (vibrate only). Heating increases vibrations (Fig. 7.4); at melting point, particles leave positions, become liquid. Melting point: minimum temperature solid melts to liquid at atmospheric pressure. Examples: Ice 0°C, Urea 133°C, Iron 1538°C (Table 7.1).
7.2.2 Liquid State
Activity 7.4: Three containers A, B, C marked 200 mL (Fig. 7.5). Fill A with water; transfer to B, then C. Water takes container shape, volume constant. Liquids no fixed shape, fixed volume; particles move freely in limited space. Attractions weaker than solids; finger through water displaces temporarily (Fig. 7.6). Heating to boiling point: vigorous movement, particles escape to vapour. Boiling point: temperature liquid boils to vapour. Evaporation: slower surface process below boiling point.
7.2.3 Gaseous State
Activity 7.5: Two gas jars A, B. Collect smoke in A (Fig. 7.7a,b); place B over, remove plate (Fig. 7.7c). Smoke fills B (Fig. 7.7d). Gases no fixed volume/shape, fill space. Particles free, negligible attractions. Can use iodine vapour (Fig. 7.8). Liquids/gases flow, called fluids.
4. How Does the Interparticle Spacing Differ in the Three States of Matter?
Activity 7.6: Let us experiment - Syringe Compression
Syringe without needle, plunger out (Fig. 7.9a). Thumb over end (b), push in (c). Air volume decreases - compressible, large spaces. Water incompressible. Gases maximum spacing, solids minimum, liquids intermediate.
Activity 7.7: Let us observe - Dissolving Solids
Half-fill vessel with water, mark A (Fig. 7.10a). Add sugar, mark B (b). Stir (c), mark C (d). Level decreases after dissolution - sugar particles occupy water spaces (Fig. 7.11). Repeat with salt/glucose (dissolve), sand/stone (don't, volume increases). Sand insoluble, settles.
Key Idea
Solids closely packed, some space (Fig. 7.12a); liquids more (b); gases maximum (c). SPM: dust particles larger than constituent particles, made of many atoms/molecules.
5. How Particles Move in Different States of Matter?
Activity 7.8: Let us experiment - Potassium Permanganate Diffusion
Water tumbler, add potassium permanganate. Streaks spread (Fig. 7.13a), uniform pink (b). Water particles in motion pull and spread solute. Insolubles like sand don't. Think like scientist: Hot, room, ice-cold water - spreads fastest in hot due to faster movement.
Activity 7.9: Let us find out - Incense Diffusion
Light incense in room corner (Fig. 7.14). Fragrance spreads. Air particles hit fragrance particles, diffusing. Examples: perfume, cooking smells.
Ever Heard Of... Soap Cleaning
Soap particles surround oil on clothes; one end attaches to oil, other to water, lifting oil (Fig. 7.15).
6. Wrap Up!
Matter made of particles held by attractions, strength depending on distance/thermal energy. Solids: low energy, close particles, strong forces. Melting: overcomes forces for liquid. Gases: high energy, free movement. Table summarizes states.
Questions and Answers from Chapter
Short Questions
Q1. The primary difference between solids and liquids is that the constituent particles are?
Answer: Closely packed in solids and move past each other in liquids.
Q2. Melting ice into water is an example of the transformation of a solid into a liquid. True or False?
Answer: True.
Q3. Melting process involves a decrease in interparticle attractions during the transformation. True or False?
Answer: True.
Q4. Solids have a fixed shape and a fixed volume. True or False?
Answer: True.
Q5. The interparticle interactions in solids are very strong, and the interparticle spaces are very small. True or False?
Answer: True.
Q6. When we heat camphor in one corner of a room, the fragrance reaches all corners of the room. True or False?
Answer: True.
Q7. On heating, we are adding energy to the camphor, and the energy is released as a smell. True or False?
Answer: False (corrected: On heating, particles move faster and spread).
Q8. If we could remove all the constituent particles from a chair, what would happen?
Answer: Nothing of the chair will remain.
Q9. Why do gases mix easily, while solids do not?
Answer: Gases have negligible interparticle attractions.
Q10. When spilled on the table, milk in a glass tumbler flows and spreads out, but the glass tumbler stays in the same shape. Why?
Answer: Milk is liquid, tumbler is solid.
Q11. Why does the water in the ocean taste salty, even though the salt is not visible?
Answer: Salt dissolves into invisible particles.
Q12. Grains of rice and rice flour take the shape of the container when placed in different jars. Are they solids or liquids?
Answer: Solids.
Q13. What is the melting point of ice?
Answer: 0°C.
Q14. What are interparticle spaces?
Answer: Spaces between particles.
Q15. What holds particles together?
Answer: Interparticle attractions.
Medium Questions
Q1. The primary difference between solids and liquids is that the constituent particles are?
Answer: The primary difference is that particles are closely packed in solids with fixed positions, while in liquids they move past each other, allowing flow. This explains why solids have fixed shape and liquids take container shape. (3 marks)
Q2. Melting ice into water is an example of the transformation of a solid into a liquid. True or False? Correct if false.
Answer: True. It involves particles gaining energy to overcome attractions, moving from fixed positions in solid to freer movement in liquid. (3 marks)
Q3. Melting process involves a decrease in interparticle attractions during the transformation. True or False? Correct if false.
Answer: True. Heating weakens attractions, allowing particles to leave positions and form liquid state. (3 marks)
Q4. Solids have a fixed shape and a fixed volume. True or False? Correct if false.
Answer: True. Due to strong attractions and minimal spacing, particles vibrate but don't move freely. (3 marks)
Q5. The interparticle interactions in solids are very strong, and the interparticle spaces are very small. True or False? Correct if false.
Answer: True. This packing gives solids definite shape and incompressibility. (3 marks)
Q6. When we heat camphor in one corner of a room, the fragrance reaches all corners of the room. True or False? Correct if false.
Answer: True. Heating causes particles to move faster and diffuse through air. (3 marks)
Q7. On heating, we are adding energy to the camphor, and the energy is released as a smell. True or False? Correct if false.
Answer: False. Heating adds energy, increasing particle movement for diffusion; smell is from particles reaching nose. (3 marks)
Q8. If we could remove all the constituent particles from a chair, what would happen?
Answer: Nothing of the chair will remain, as it's composed entirely of particles; removing them eliminates the matter. (3 marks)
Q9. Why do gases mix easily, while solids do not?
Answer: Gases have negligible attractions and maximum spacing, allowing free mixing; solids have strong attractions preventing movement. (3 marks)
Q10. When spilled on the table, milk in a glass tumbler flows and spreads out, but the glass tumbler stays in the same shape. Justify.
Answer: Milk is liquid with weaker attractions, allowing flow; tumbler is solid with strong attractions maintaining shape. (3 marks)
Q11. Why does the water in the ocean taste salty, even though the salt is not visible? Explain.
Answer: Salt dissolves into tiny particles occupying spaces in water, invisible but detectable by taste. (3 marks)
Q12. Grains of rice and rice flour take the shape of the container when placed in different jars. Are they solids or liquids? Explain.
Answer: They are solids; particles flow like fluids but have fixed volume and strong attractions internally. (3 marks)
Q13. What happens when sugar dissolves in water?
Answer: Sugar breaks into particles occupying interparticle spaces in water, becoming invisible but present. (3 marks)
Q14. Why can't solids be compressed easily?
Answer: Particles are closely packed with minimal interparticle spaces and strong attractions. (3 marks)
Q15. How do particles behave in gases?
Answer: Particles move freely in all directions with negligible attractions and maximum spacing. (3 marks)
Long Questions
Q1. The primary difference between solids and liquids is that the constituent particles are?
Answer: The primary difference between solids and liquids is that the constituent particles are closely packed in solids, while they are stationary in liquids (incorrect option); far apart in solids and have fixed position in liquids (incorrect); always moving in solids and have fixed position in liquids (incorrect); closely packed in solids and move past each other in liquids (correct). This difference arises because in solids, interparticle attractions are strong, keeping particles in fixed positions allowing only vibrations, whereas in liquids, attractions are weaker, enabling particles to slide past each other, giving liquids flow and no fixed shape but fixed volume.
Q2. Which of the following statements are true? Correct the false statements.
Answer: (i) True: Melting ice is solid to liquid. (ii) True: Decrease in attractions. (iii) True: Fixed shape and volume. (iv) True: Strong interactions, small spaces. (v) True: Fragrance reaches due to diffusion. (vi) False: On heating, energy increases particle movement for diffusion, not released as smell; smell is from particles stimulating senses. These statements highlight properties of states, changes, and particle behavior in matter.
Q3. Choose the correct answer with justification. If we could remove all the constituent particles from a chair, what would happen?
Answer: Nothing of the chair will remain. Justification: Matter like the chair is composed entirely of constituent particles (atoms/molecules); removing them eliminates the substance, as demonstrated by activities showing matter breaks into particles without changing composition.
Q4. Why do gases mix easily, while solids do not?
Answer: Gases mix easily because interparticle attractions are negligible, particles are far apart with maximum spacing, allowing free movement and diffusion, as shown in incense activity. Solids do not mix as particles are closely packed with strong attractions, fixed positions, only vibrating, preventing mixing without external force like grinding.
Q5. When spilled on the table, milk in a glass tumbler flows and spreads out, but the glass tumbler stays in the same shape. Justify this statement.
Answer: Milk flows as it's a liquid with weaker interparticle attractions, allowing particles to move freely within limited space, taking the table's shape. The tumbler stays shaped as it's a solid with strong attractions, particles in fixed positions, maintaining definite shape and volume, as per Activity 7.4.
Q6. Represent diagrammatically the changes in the arrangement of particles as ice melts and transforms into water vapour.
Answer: In ice (solid): Particles closely packed in fixed positions. On melting to water (liquid): Particles slightly farther, move past each other. To vapour (gas): Particles far apart, move freely. Diagram shows transition from ordered lattice to disordered liquid to random gas, with increasing spacing and decreasing attractions.
Q7. Draw a picture representing particles present in the following: (i) Aluminium foil (ii) Glycerin (iii) Methane gas
Answer: (i) Aluminium foil (solid): Closely packed particles in fixed positions. (ii) Glycerin (liquid): Particles close but sliding past each other. (iii) Methane gas: Particles far apart, moving randomly. Pictures illustrate minimal spacing in solid, more in liquid, maximum in gas.
Q8. Observe Fig. 7.16a which shows the image of a candle that was just extinguished after burning for some time. Identify the different states of wax in the figure and match them with Fig. 7.16b showing the arrangement of particles.
Answer: In candle: Solid wax at base (closely packed particles), melted liquid wax near wick (particles moving), vaporized gas (particles far apart). Match to Fig. 7.16b: Solid to ordered, liquid to semi-ordered, gas to random arrangements, showing state changes due to heat.
Q9. Why does the water in the ocean taste salty, even though the salt is not visible? Explain.
Answer: Salt dissolves in water, breaking into tiny invisible particles that occupy interparticle spaces, as in Activity 7.2. Particles are too small to see but detectable by taste; solution volume less than sum indicates spaces filled without new substance formation.
Q10. Grains of rice and rice flour take the shape of the container when placed in different jars. Are they solids or liquids? Explain.
Answer: They are solids. Though appearing to flow like liquids, particles have strong internal attractions, fixed volume; behavior due to small size allowing sliding, but unlike liquids, no true flow without boundaries, as solids have minimal spacing.
Q11. Explain why sugar dissolves in water but sand does not.
Answer: Sugar dissolves as its particles separate and occupy interparticle spaces in water due to compatible attractions; sand does not as particles held by stronger attractions, insoluble, settling and increasing volume, as per Activity 7.7.
Q12. Describe the movement of particles in liquids using an activity.
Answer: In Activity 7.8, potassium permanganate in water spreads color uniformly due to constant motion of water particles pulling and hitting solute particles; faster in hot water, showing increased movement with temperature.
Q13. How does interparticle spacing differ in gases from solids and liquids?
Answer: Gases have maximum spacing, compressible as in syringe activity; solids minimal, incompressible; liquids intermediate, slightly compressible, explaining properties like diffusion in gases vs. fixed shape in solids.
Q14. What happens to particles during melting and boiling?
Answer: During melting, particles vibrate vigorously, weakening attractions to form liquid; boiling sees particles escape as vapor, with bubble formation, as energy overcomes forces, transitioning states.
Q15. Explain Acharya Kanad's contribution to the idea of matter.
Answer: Acharya Kanad proposed 'Parmanu' as tiny, indivisible eternal particles making matter, in Vaisheshika Sutras; aligns with modern view of atoms/molecules as building blocks, predating Western ideas.
