Table of Contents
Introduction
- What is Matter?
- Anything that has mass and takes up space is called matter.
- Everything around us (like a book, water, or air) is matter.
- Three States of Matter:
- Solid: (e.g., Wood, Ice)
- Has a fixed shape and fixed volume.
- Particles are tightly packed with strong forces between them.
- They cannot be compressed and do not flow.
- Liquid: (e.g., Milk, Water)
- Has a fixed volume but no fixed shape. It takes the shape of its container.
- Particles are less tightly packed than solids. Forces are weaker, so liquids can flow.
- They cannot be compressed easily.
- Gas: (e.g., Oxygen, Smoke)
- Has no fixed shape and no fixed volume. It fills the entire container.
- Particles are very far apart with very weak forces between them.
- Gases can be compressed easily and flow in all directions.
- Solid: (e.g., Wood, Ice)
- Recall and Unwind (Answers):
Let’s fill the blanks using > (greater than) for more, and < (less than) for less.- Intermolecular Force: Solids > Liquids > Gases
- Intermolecular Space: Solids < Liquids < Gases
- Compressibility: Solids < Liquids < Gases
- Rigidity: Solids > Liquids > Gases
- Matter क्या है?
- जिस भी चीज़ का द्रव्यमान (mass) होता है और जो जगह घेरती है (occupies space) , उसे matter कहते हैं।
- हमारे आस-पास की हर चीज़ (जैसे किताब, पानी, हवा) matter है।
- Matter की तीन States (अवस्थाएं):
- ठोस (Solid): (जैसे- लकड़ी, बर्फ)
- इनका एक fixed shape ( निश्चित आकार ) और fixed volume ( निश्चित आयतन ) होता है।
- इनके particles आपस में बहुत पास-पास होते हैं और उनके बीच force बहुत strong होता है।
- ये दबाए नहीं जा सकते (incompressible) और बहते नहीं (cannot flow) हैं।
- तरल (Liquid): (जैसे- दूध, पानी)
- इनका fixed volume (निश्चित आयतन) होता है लेकिन fixed shape नहीं होता। ये जिस बर्तन में डाले जाते हैं उसी का आकार ले लेते हैं।
- इनके particles solids के मुकाबले थोड़े दूर-दूर होते हैं। Forces कमजोर होते हैं, इसलिए liquids बह सकते (flow) हैं।
- ये भी दबाए नहीं जा सकते।
- गैस (Gas): (जैसे- ऑक्सीजन, धुआं)
- इनका ना कोई fixed shape होता है ना fixed volume। ये पूरे container में फैल जाती हैं।
- इनके particles बहुत ज्यादा दूर-दूर होते हैं और उनके बीच force बहुत weak होता है।
- Gases आसानी से दबाई (compressible) जा सकती हैं और हर दिशा में flow करती हैं।
- ठोस (Solid): (जैसे- लकड़ी, बर्फ)
- Recall and Unwind (जवाब):
चलिए खाली जगह को > (greater than/ज्यादा) और < (less than/कम) से भरते हैं।- Intermolecular Force (आकर्षण बल): Solids > Liquids > Gases
- Intermolecular Space (रिक्त स्थान): Solids < Liquids < Gases
- Compressibility ( संपीड्यता ): Solids < Liquids < Gases
- Rigidity ( कठोरता ): Solids > Liquids > Gases
Kinetic Molecular Theory of Matter
Imagine you are trying to understand why ice is hard, water flows, and air is all around us. The Kinetic Molecular Theory is like a set of rules that scientists use to explain this.
- What is it?
It is a theory (a well-explained idea) that tells us what matter is made of and how it behaves. - The Main Idea:
- All matter (everything around us) is made up of very, very tiny particles. These particles can be atoms or molecules.
- These tiny particles are always moving. Because they are moving, they have energy. This energy of movement is called kinetic energy.
- The Rules (Postulates) of the Theory:
- Rule 1: Matter is made of a huge number of tiny particles (atoms or molecules).
- Rule 2: These particles are always moving. They never sit completely still. This movement gives them kinetic energy.
- Rule 3: The particles move in random directions (everywhere!). They keep bumping into each other and when they collide, they transfer energy to each other.
- Rule 4: When particles gain or lose a lot of energy (like when we heat or cool something), it can cause a change of state (e.g., solid ice can become liquid water).
- Rule 5: There is empty space between these particles. This space is called intermolecular space.
- Rule 6: There is an invisible force of attraction that pulls the particles towards each other. This is called intermolecular force of attraction.
- This force becomes weaker if the space between particles is large.
- This force becomes stronger if the space between particles is small.
चलो एक कहानी की तरह समझते हैं। यह theory हमें बताती है कि ठोस, तरल, गैस अलग-अलग क्यों दिखते और अलग – अलग behave क्यों करते हैं।
- यह क्या है?
यह एक सिद्धांत (theory) है जो हमें बताता है कि matter किससे बना होता है और उसके छोटे-छोटे particles कैसे behave करते हैं। - मुख्य बात:
- सारा matter (हमारे आस-पास की सभी चीज़ें) बहुत ही छोटे-छोटे particles से मिलकर बना होता है। ये particles atoms या molecules होते हैं।
- ये tiny particles हमेशा हिलते-डुलते (move) रहते हैं। क्योंकि वे move कर रहे हैं, उनमें energy होती है। इस movement की energy को kinetic energy कहते हैं।
- सिद्धांत के नियम (Postulates):
- नियम 1: Matter बहुत सारे tiny particles (atoms or molecules) से मिलकर बना होता है।
- नियम 2: ये particles लगातार motion में रहते हैं। वे कभी पूरी तरह still नहीं बैठते। इस movement के कारण उनमें kinetic energy होती है।
- नियम 3: Particles random directions में चलते हैं (इधर-उधर!)। वे एक-दूसरे से टकराते (collide) रहते हैं और जब टकराते हैं, तो वे एक-दूसरे को energy transfer करते हैं।
- नियम 4: जब particles बहुत ज़्यादा energy gain या lose करते हैं (जैसे किसी चीज़ को गर्म या ठंडा करने पर), तो इससे उसकी state change हो सकती है (जैसे, बर्फ पिघलकर पानी बन जाती है)।
- नियम 5: इन particles के बीच में खाली जगह (empty space) होती है। इस space को intermolecular space कहते हैं।
- नियम 6: Particles के बीच एक अदृश्य आकर्षण बल (invisible force of attraction) होता है जो उन्हें एक-दूसरे की तरफ खींचता है। इसे intermolecular force of attraction कहते हैं।
- अगर particles के बीच की space ज़्यादा है तो यह force कमज़ोर हो जाता है।
- अगर particles के बीच की space कम है तो यह force मजबूत होता है।
Brownian Motion
Brownian motion is the name given to the random, zig-zag movement of tiny particles floating in a liquid or a gas.
A Scottish scientist named Robert Brown was looking at tiny pollen grains in water under a microscope. He noticed that the grains were not staying still. They were constantly jiggling and moving in a random, shaky path, like they were being bumped by invisible things.
We now know that this movement happens because the particles are constantly being bumped and hit by the even smaller, fast-moving molecules of the water (or air) they are floating in. These molecules are always moving (as per the Kinetic Theory) and their collisions push the larger pollen grains around, causing the zig-zag motion.
Diffusion
What is Diffusion?
Diffusion is the process where particles of a substance automatically spread out from a place where there are many of them (high concentration) to a place where there are few of them (low concentration). They do this until they are evenly mixed everywhere.
A Simple Example:
Imagine you open a bottle of perfume at one end of a room. Slowly, the smell spreads to the entire room. This is because the perfume particles move from the bottle (where they are crowded) into the air of the room (where there are none) until the smell is equally strong everywhere.
Diffusion in Different States:
- In Gases: Gases diffuse very fast and easily. Why? Because their particles have a lot of space between them and move very quickly in all directions.
- Example: The smell of cooking food reaches you quickly.
- In Liquids: Liquids also diffuse, but slower than gases. Their particles are closer but can still move around and mix.
- There are two types of liquids:
- Miscible Liquids: Liquids that can mix completely with each other. E.g., Milk and water, lemon juice in water.
- Immiscible Liquids: Liquids that do not mix with each other. E.g., Oil and water.
- There are two types of liquids:
- In Solids: Solids do not show diffusion easily (or show it very, very slowly). Why? Because their particles are packed tightly together and can only vibrate in their fixed positions. They cannot move around to mix.
- Example: If you put two different metal blocks together, their atoms will not mix for a very long time.
Diffusion क्या है?
Diffusion एक ऐसी process है जिसमें किसी substance के particles अपने आप फैल जाते हैं, उस जगह से जहाँ उनकी संख्या ज़्यादा (high concentration) है वहाँ से उस जगह की तरफ जहाँ उनकी संख्या कम (low concentration) है। वह ऐसा तब तक करते हैं जब तक वह हर जगह एक जैसे (evenly mixed) नहीं मिल जाते।
एक आसान Example:
मान लो तुम किसी एक room के एक कोने में perfume की bottle खोलते हो। धीरे-धीरे, उसकी खुशबू पूरे room में फैल जाती है। ऐसा इसलिए होता है क्योंकि perfume के particles bottle (जहाँ वे crowded हैं) से room की हवा में (जहाँ शुरू में कोई नहीं हैं) फैलते हैं जब तक खुशबू हर जगह एक जैसी नहीं हो जाती।
अलग-अलग States में Diffusion:
- Gases में : Gases बहुत तेज़ी और आसानी से diffuse होती हैं। क्यों? क्योंकि उनके particles के बीच बहुत ज़्यादा space होता है और वे बहुत तेज़ी से हर दिशा में move करते हैं।
- Example : खाना बनने की smell तुरंत तुम तक पहुँच जाती है।
- Liquids में : Liquids भी diffuse होते हैं, लेकिन gases से धीमी गति से। उनके particles पास-पास होते हैं लेकिन फिर भी इधर-उधर move करके mix हो सकते हैं।
- Liquids दो तरह के होते हैं:
- Miscible Liquids: वे liquids जो एक-दूसरे में पूरी तरह mix हो जाते हैं। जैसे- दूध और पानी, नींबू का रस पानी में।
- Immiscible Liquids: वे liquids जो एक-दूसरे में mix नहीं होते। जैसे- तेल और पानी।
- Liquids दो तरह के होते हैं:
- Solids में: Solids आसानी से diffusion नहीं दिखाते (या बहुत बहुत धीमी गति से दिखाते हैं)। क्यों? क्योंकि उनके particles बहुत टाइट पैक रहते हैं और सिर्फ अपनी जगह पर vibrate कर सकते हैं। वे इधर-उधर move होकर mix नहीं हो पाते।
- Example: अगर तुम दो अलग-अलग metal के blocks आपस में जोड़ोगे, उनके atoms बहुत लंबे time तक mix नहीं होंगे।
Answers to “Think about it”
Question: Which of these substances will exhibit Brownian movement? Give reason for each.
- Pen or juice
- Answer: Juice
- Reason: Juice is a liquid. Its particles are moving and can be bumped by smaller water molecules, showing Brownian motion. A pen is a solid. Its particles are fixed and only vibrate, so we cannot see Brownian motion in it.
- Carbon dioxide or paper
- Answer: Carbon dioxide
- Reason: Carbon dioxide is a gas. Its particles move very fast and freely, constantly colliding and showing Brownian motion. Paper is a solid, so its particles cannot move around freely.
- Steam or honey
- Answer: Steam
- Reason: Steam is water in its gaseous state. The fast-moving gas particles will show Brownian motion. Honey is a very thick (viscous) liquid. Its particles move very slowly, so Brownian motion is very hard to see compared to a gas.
States of Matter Based on Kinetic Molecular Theory
How do we decide the State of Matter?
The state of matter (solid, liquid, or gas) depends on two main things:
- Intermolecular Force of Attraction : How strongly the particles attract each other.
- Intermolecular Space : How much empty space is between the particles.
The Kinetic Molecular Theory uses these two ideas to explain why solids, liquids, and gases behave so differently.
1. Solids (ठोस)
- Packing of Particles: The molecules are very, very close together (closely packed). There is almost no space between them.
- Force of Attraction: Because the particles are so close, the force that pulls them together is the strongest.
- Movement: The particles cannot move from their positions. They don’t have enough energy to break the strong force. They can only vibrate (shake) in their fixed spots.
- Result: This is why solids are hard, have a fixed shape, and a fixed volume.
- Particles की स्थिति: Solids के molecules बहुत ही पास-पास (closely packed) होते हैं। उनके बीच लगभग कोई space नहीं होता (negligible space)।
- आकर्षण बल (Force of Attraction) : क्योंकि particles बहुत पास होते हैं, इसलिए उनके बीच का आपस में खिचाव का बल (Force of Attraction) सबसे मजबूत (strongest) होता है।
- Movement : Particles अपनी जगह से move नहीं कर सकते। उनमें इतनी energy नहीं होती कि वह इस strong force को तोड़ सकें। वे सिर्फ अपनी fixed जगह पर काँप (vibrate) सकते हैं।
- नतीजा (Result): इसीलिए solids hard होते हैं, और उनका एक fixed shape और fixed volume होता है।
Question: Match the following.
| Column A | Column B |
|---|---|
| (a) Tiffin box | (i) Highest intermolecular force |
| (b) Cough syrup | (ii) Highest intermolecular space |
| (c) Smoke | (iii) Molecules of similar type |
| (d) Cohesion | (iv) Molecules of different type |
| (e) Adhesion | (v) Fixed volume |
Answers and Explanations
1. (a) Tiffin box → (i) Highest intermolecular force
- Explanation: A tiffin box is made of metal or plastic, which is a solid. In solids, the molecules are packed very tightly together. This means the force of attraction between the molecules (intermolecular force) is the strongest.
- Tiffin box metal या plastic का बना होता है, जो एक solid (ठोस) है। Solids में molecules बहुत Tight Pack रहते हैं। इसका मतलब है कि molecules के बीच का आकर्षण बल (Force of Attraction) सबसे मजबूत (strongest) होता है।
2. (b) Cough syrup → (v) Fixed volume
- Explanation: Cough syrup is a liquid. A key property of liquids is that they have a fixed volume. Even though they take the shape of their container, the amount of space they occupy (their volume) does not change easily.
- Cough syrup एक liquid (तरल) है। Liquids की एक मुख्य property यह है कि उनका एक fixed volume (निश्चित आयतन) होता है। भले ही वे अपने container का आकार ले लें, लेकिन उनके द्वारा घेरी गई जगह (volume) आसानी से नहीं बदलती।
3. (c) Smoke → (ii) Highest intermolecular space
- Explanation: Smoke is a gas. In gases, the molecules are very far apart from each other. This means the empty space between the molecules (intermolecular space) is the largest compared to solids and liquids.
- Smoke एक gas (गैस) है। Gases में molecules एक-दूसरे से बहुत दूर होते हैं। इसका मतलब है कि molecules के बीच की खाली जगह (intermolecular space) solids और liquids की तुलना में सबसे ज़्यादा (largest) होती है।
4. (d) Cohesion → (iii) Molecules of similar type
- Explanation: Cohesion is the force of attraction that acts between molecules of the same kind of substance. For example, it is the force that holds water molecules together to form a drop.
- Cohesion (संसजन बल) वह आकर्षण बल है जो एक ही तरह (similar type) के molecules के बीच काम करता है। उदाहरण के लिए, यही बल पानी के molecules को आपस में जोड़कर एक बूंद बनाता है।
5. (e) Adhesion → (iv) Molecules of different type
- Explanation: Adhesion is the force of attraction that acts between molecules of different substances. For example, it is the force that makes water stick to the glass of a window.
- Adhesion (आसंजन बल) वह आकर्षण बल है जो अलग-अलग तरह (different type) के molecules के बीच काम करता है। उदाहरण के लिए, यही बल पानी को किसी शीशे की खिड़की पर चिपकाए रखता है।
Properties of States of Matter & Kinetic Energy
This part of the chapter tells us two main things:
1. What decides if matter will change its state?
The change of state (like solid ice melting into liquid water) depends on two things:
- Intermolecular Space: The amount of empty space between the particles.
- Intermolecular Force: The strength of the invisible force that pulls the particles together.
When we heat or cool a substance, we are changing these two things. For example:
- On Heating: Particles get more energy, start moving faster, need more space, and the force between them becomes weaker. This can change a solid to a liquid or a liquid to a gas.
- On Cooling: Particles lose energy, move slower, need less space, and the force between them becomes stronger. This can change a gas to a liquid or a liquid to a solid.
2. The link between Temperature and Kinetic Energy
- Kinetic Energy is the energy of movement. Particles that are moving have kinetic energy.
- Temperature is a measure of how fast the particles of a substance are moving on average.
The important rule is:
As the temperature increases, the kinetic energy of the particles also increases.
यह हिस्सा हमें दो मुख्य बातें बताता है:
1. Matter की state कब बदलती है?
Matter की state का बदलना ( जैसे ठोस बर्फ का पिघलकर तरल पानी बनना ) दो चीज़ों पर निर्भर करता है:
- Intermolecular Space : Particles के बीच की खाली जगह।
- Intermolecular Force : Particles को आपस में खींचने वाला अदृश्य बल।
जब हम किसी चीज़ को गर्म या ठंडा करते हैं, तो हम इन दोनों चीज़ों को बदल रहे होते हैं। जैसे :
- गर्म करने पर : Particles को ज़्यादा energy मिलती है, वे तेज़ी से हिलने लगते हैं, उन्हें ज़्यादा जगह चाहिए होती है, और उनके बीच का Force कमज़ोर पड़ जाता है। इससे Solids चीज़ें Liquids बन सकती है या Liquid चीज़ें Gases बन सकती है।
- ठंडा करने पर : Particles की energy कम हो जाती है, वे धीरे चलते हैं, उन्हें कम जगह चाहिए होती है, और उनके बीच का Force मजबूत हो जाता है। इससे Gases convert Liquid हो सकते है या Liquids convert हो सकते है Solids में।
2. Temperature और Kinetic Energy का कनेक्शन
- Kinetic Energy : movement की energy है। जो particles move कर रहे हैं, उनमें kinetic energy होती है।
- Temperature : यह मापता है कि किसी substance के particles औसतन कितनी तेज़ी से move कर रहे हैं।
यहाँ महत्वपूर्ण नियम है:
जैसे-जैसे temperature बढ़ता है, वैसे-वैसे particles की kinetic energy भी बढ़ती है।
Properties of Solids, Liquids, and Gases
1. Properties of SOLIDS
- Shape and Volume: Solids have a fixed shape and a fixed volume.
- Particles: The molecules are closely packed with very little space between them.
- Movement: The particles cannot move from their spots. They only vibrate in their fixed positions.
- Force: The intermolecular force is very strong.
- Energy: They have low kinetic energy.
- Effect of Temperature: When temperature changes, the kinetic energy of the particles changes.
- Shape और Volume: Solids का एक fixed shape होता है और एक fixed volume होता है।
- Particles: Solid के molecules बहुत पास-पास (closely packed) होते हैं। उनके बीच बहुत कम space होता है।
- Movement: ये particles अपनी जगह से move नहीं कर सकते। वे सिर्फ अपनी जगह पर काँपते (vibrate) रहते हैं।
- Force: Particles के बीच जो intermolecular force है, वह बहुत strong होता है।
- Energy: उनमें kinetic energy बहुत कम होती है।
- Temperature का effect: जब temperature बदलती है, तो particles की kinetic energy बदल जाती है।
2. Properties of LIQUIDS
- Shape and Volume: Liquids have no fixed shape but they have a fixed volume. They take the shape of their container.
- Particles: The molecules are less closely packed than in solids. There is more space between them.
- Movement: The particles can move around and slide past each other. This is why liquids flow.
- Force: The intermolecular force is weaker than in solids.
- Effect of Temperature: When temperature changes, the kinetic energy of the particles changes.
- Shape और Volume: Liquids का कोई fixed shape नहीं होता, लेकिन उनका एक fixed volume होता है। वे अपने container का shape ले लेते हैं।
- Particles: Liquid के molecules solid के मुकाबले थोड़े दूर (less closely packed) होते हैं। उनके बीच ज़्यादा space होता है।
- Movement: Particles इधर-उधर move कर सकते हैं और एक-दूसरे के पास से slide कर सकते हैं। इसीलिए liquids flow कर सकते हैं।
- Force: Particles के बीच जो intermolecular force है, वह solid से weaker होता है।
- Temperature का effect: जब temperature बदलती है, तो particles की kinetic energy बदल जाती है।
3. Properties of GASES
- Shape and Volume: Gases have no fixed shape and no fixed volume. They fill their entire container.
- Particles: The molecules are very far apart. The intermolecular space is the maximum.
- Movement: The particles move very fast and randomly in all directions.
- Force: The intermolecular force is very weak (almost zero).
- Collisions: When they collide, it is elastic (no loss of energy).
- Effect of Temperature: When temperature changes, the kinetic energy of the particles changes.
- Shape और Volume: Gases का ना कोई fixed shape होता है ना fixed volume। वे पूरे container को भर देती हैं।
- Particles: Gas के molecules बहुत दूर-दूर (very far apart) होते हैं। उनके बीच की space सबसे ज़्यादा (maximum) होती है।
- Movement: Particles बहुत तेज़ और अनियमित (randomly) तरीके से हर direction में move करते हैं।
- Force: Particles के बीच जो intermolecular force है, वह बहुत weak होता है।
- Collisions: जब वे आपस में टकराते (collide) हैं, तो वह elastic होता है (energy loss नहीं होता)।
- Temperature का effect: जब temperature बदलती है, तो particles की kinetic energy बदल जाती है।
Change of State of Matter
What is Change of State?
It is when a substance changes from one physical state to another. For example, when solid ice changes to liquid water.
Why does this happen?
This change happens because of two things:
- The movement of its molecules.
- The force that holds the molecules together.
What happens when we HEAT a substance? (Adding Energy)
Example: Solid Ice to Liquid Water to Water Vapour
- Heating a Solid:
- When we heat a solid, its molecules gain energy (kinetic energy).
- They start vibrating faster.
- They try to overcome the force holding them together.
- The space between molecules increases.
- The force between molecules becomes weaker.
- Finally, the solid melts and becomes a liquid.
- Heating a Liquid:
- On further heating, the liquid molecules gain even more energy.
- They start moving around randomly very fast.
- The space between them increases even more.
- The force between them becomes very weak.
- Finally, the liquid boils and becomes a gas.
गर्म करने पर क्या होता है? (Adding Energy)
- Solid को गर्म करना:
- जब हम solid को गर्म करते हैं, उसके molecules energy gain करते हैं।
- वे तेज़ हिलने लगते हैं।
- वे उन्हें पकड़ कर रखने वाले force को overcome करने की कोशिश करते हैं।
- Molecules के बीच का space बढ़ जाता है।
- Molecules के बीच का force कमज़ोर हो जाता है।
- आखिर में, solid पिघल कर liquid बन जाता है।
- Liquid को गर्म करना:
- ज़्यादा गर्म करने पर, liquid के molecules और भी ज़्यादा energy gain करते हैं।
- वे बहुत तेज़ और randomly move करने लगते हैं।
- उनके बीच का space और बढ़ जाता है।
- उनके बीच का force बहुत weak हो जाता है।
- आखिर में, liquid उबल कर gas बन जाती है।
What happens when we COOL a substance? (Removing Energy)
Example: Water Vapour to Liquid Water to Solid Ice
- When we cool a substance, its molecules lose energy.
- They start moving slower.
- The force of attraction between them increases.
- The molecules come closer together, so the space between them decreases.
- With more cooling, a gas changes to a liquid (like steam becoming water droplets).
- With even more cooling, the liquid changes to a solid (like water freezing into ice).
ठंडा करने पर क्या होता है? (Removing Energy)
- जब हम किसी चीज़ को ठंडा करते हैं, उसके molecules energy lose करते हैं।
- वे धीमे move करने लगते हैं।
- उनके बीच का आकर्षण बल (force of attraction) बढ़ जाता है।
- Molecules एक-दूसरे के पास आने लगते हैं, इसलिए उनके बीच का space कम हो जाता है।
- ज़्यादा cooling से, gas liquid बन जाती है (जैसे steam के water की बूंदें बन जाना)।
- और ज़्यादा cooling से, liquid solid बन जाता है (जैसे पानी freeze होकर बर्फ बन जाना)।
Terms Related to Change of State of Matter
1. Fusion (Melting)
- What it is: The process where a solid changes into a liquid by absorbing heat.
- Important Point: During melting, the temperature does not change until all the solid has become liquid.
- Melting Point: The fixed temperature at which a solid melts.
- Example: Ice (solid) melts into water (liquid) at 0°C.
- यह क्या है : वह process जहाँ एक solid, heat सोखकर (absorbing heat), liquid में बदल जाता है।
- महत्वपूर्ण बात : पिघलने के दौरान, temperature नहीं बदलती जब तक सारा solid liquid नहीं बन जाता।
- Melting Point : वह fixed temperature जिस पर solid पिघलता है।
- उदाहरण : बर्फ (solid) पिघलकर पानी (liquid) 0°C पर बनती है।
2. Vaporisation (Boiling)
- What it is : The process where a liquid changes into its vapour or gas by absorbing heat at a constant temperature.
- How it happens : This happens through boiling.
- Boiling Point : The fixed temperature at which a liquid starts to boil.
- Example : Water (liquid) boils and becomes steam (gas) at 100°C.
- यह क्या है : वह process जहाँ एक liquid, heat सोखकर, एक constant temperature पर अपनी gas अवस्था में बदल जाता है।
- यह कैसे होता है : यह उबालने (boiling) से होता है।
- Boiling Point : वह fixed temperature जिस पर liquid उबलना शुरू करता है।
- उदाहरण : पानी (liquid) उबलकर भाप (gas) 100°C पर बनता है।
3. Solidification (Freezing)
- What it is: The process where a liquid changes into a solid by releasing heat at a constant temperature.
- Freezing Point: The constant temperature at which a liquid changes into a solid.
- Example: Water (liquid) freezes and becomes ice (solid) at 0°C.
- Note: The melting point of a solid is the same as the freezing point of its liquid.
- यह क्या है: वह process जहाँ एक liquid, heat छोड़कर (releasing heat), एक constant temperature पर solid में बदल जाता है।
- Freezing Point: वह constant temperature जिस पर liquid solid बन जाता है।
- उदाहरण: पानी (liquid) जमकर बर्फ (solid) 0°C पर बनता है।
- नोट: एक solid का melting point उसके liquid के freezing point के बराबर होता है।
4. Condensation
- What it is: The process where a gas changes into its liquid state at a particular temperature.
- Condensation Point: The fixed temperature at which a gas changes to a liquid.
- Important Point: For most substances, the condensation point and boiling point are the same. The difference is that heat is absorbed during boiling, but heat is released during condensation.
- Example: Steam (gas) cools down and condenses into water droplets (liquid).
- यह क्या है: वह process जहाँ एक gas एक particular temperature पर अपनी liquid अवस्था में बदल जाता है।
- Condensation Point: वह fixed temperature जिस पर gas liquid बन जाती है।
- महत्वपूर्ण बात: ज़्यादातर substances के लिए, condensation point और boiling point एक ही होते हैं। फर्क सिर्फ इतना है कि उबालने पर heat सोखी जाती है, लेकिन condensation पर heat छोड़ी जाती है।
- उदाहरण: भाप (gas) ठंडी होकर घन्नीभूत (condenses) होकर पानी की बूंदों (liquid) में बदल जाती है।
5. Sublimation
- What it is: The process where a substance directly changes from its solid state to its gaseous state without becoming a liquid in between.
- Example: Camphor (solid) slowly changes into gaseous form at room temperature.
- यह क्या है: वह process जहाँ एक substance बीच में liquid बने बिना, सीधे अपनी solid अवस्था से gaseous अवस्था में बदल जाता है।
- उदाहरण: कपूर (solid) room temperature पर ही धीरे-धीरे gaseous form में बदल जाता है।
6. Deposition
- What it is: The process where a substance directly changes from its gaseous state into its solid state without becoming a liquid in between.
- Example: On cooling, the vapour from naphthalene balls (used in toilets) directly changes back into solid naphthalene.
- यह क्या है: वह process जहाँ एक substance बीच में liquid बने बिना, सीधे अपनी gaseous अवस्था से solid अवस्था में बदल जाता है।
- उदाहरण: ठंडा करने पर, नेफ्थलीन बॉल्स (toilets में use होती हैं) की vapour सीधे solid नेफ्थलीन में बदल जाती है।
Evaporation
What is Evaporation?
Evaporation is the process where a liquid slowly changes into its gaseous state (vapour) without boiling.
Key Point: This happens below the boiling point of the liquid. The liquid does not need to be heated until it boils to turn into vapour.
Everyday Example:
Have you noticed that wet utensils dry up on their own after you wash them? This is because of evaporation. The water on the utensils slowly turns into water vapour and disappears into the air, without anyone boiling it.
Evaporation vs. Boiling (Vaporisation):
| Feature | Evaporation | Boiling (Vaporisation) |
|---|---|---|
| Temperature | Happens below the boiling point, at any temperature. | Happens only at the boiling point. |
| Speed | A slow process. | A fast and rapid process. |
| Location | Happens only from the surface of the liquid. | Happens from all parts of the liquid, forming bubbles. |
यह क्या है?
Evaporation वह process है जहाँ एक liquid धीरे-धीरे अपनी gaseous state (vapour) में बदल जाता है बिना उबले।
मुख्य बात: यह liquid के boiling point से नीचे के temperature पर होता है। Liquid को vapour में बदलने के लिए उबालना ज़रूरी नहीं है।
रोज़मर्रा का उदाहरण:
क्या तुमने गौर किया है कि बर्तन धोने के बाद वे अपने आप सूख जाते हैं? यह evaporation की वजह से होता है। बर्तनों पर का पानी धीरे-धीरे water vapour में बदलकर हवा में मिल जाता है, बिना उबाले।
Evaporation और Boiling (Vaporisation) में अंतर:
| Feature | Evaporation | Boiling (Vaporisation) |
|---|---|---|
| Temperature | Boiling point से नीचे किसी भी temperature पर होता है। | सिर्फ boiling point पर होता है। |
| Speed | एक धीमी (slow) process है। | एक तेज़ और rapid process है। |
| Location | सिर्फ liquid की सतह (surface) से होता है। | Liquid के सभी हिस्सों से होता है, bubbles बनते हैं। |
Of course! Here is a simple explanation of the Law of Conservation of Mass.
Topic: Law of Conservation of Mass
What is the Law?
The Law of Conservation of Mass states a very simple but important rule:
Mass can neither be created nor destroyed.
This means that in any change—whether it’s physical (like melting ice) or chemical (like burning wood)—the total mass of all substances involved stays the same before and after the change.
- The shape, size, or volume of matter may change.
- But the total mass always remains constant.
Why is this true?
This law holds true because the atoms that make up everything are stable. They are not created or destroyed in a change; they are just rearranged.
Scientist: Antoine Lavoisier
He is the scientist who clearly stated this law in the 18th century. He is often called the “Father of Modern Chemistry.”
Examples to Understand the Law
Example 1: Melting Ice (Physical Change)
- What you do: Add 30 grams of ice to 50 grams of water in a glass.
- Mass before melting: 30 g (ice) + 50 g (water) = 80 grams
- What happens: The ice melts and turns into water.
- Mass after melting: The total water in the glass = 80 grams
Conclusion: The mass before and after the change is the same. Mass was conserved.
Example 2: Burning Wood (Chemical Change)
- What you see: When wood burns, it leaves behind only a little ash. It seems like mass is lost.
- What actually happens:
- The wood reacts with oxygen from the air.
- The burnt wood (ash) has less mass, but the missing mass has not disappeared!
- It has escaped into the air as gases like carbon dioxide (CO₂), carbon monoxide (CO), and water vapour.
- Mass before burning = Mass of wood + Mass of oxygen used from the air
- Mass after burning = Mass of ash + Mass of gases produced (CO₂, CO, etc.)
Conclusion: If you could collect and measure all the substances (the ash AND the gases), the total mass would be equal to the mass of the wood and oxygen before burning.
Example 3: Burning Magnesium (Chemical Reaction)
- Reaction: Magnesium + Oxygen → Magnesium Oxide
- Mass of Reactants: 48 g of Magnesium + ? g of Oxygen
- Mass of Product: 80 g of Magnesium Oxide
- To find the mass of oxygen used: 80 g (product) – 48 g (magnesium) = 32 g of oxygen.
- So, 48 g + 32 g = 80 g. The total mass of reactants equals the total mass of the product.
The Key Idea in a Chemical Reaction:
- The reactants (starting substances) break apart into atoms.
- These atoms then rearrange themselves to form new products (new substances).
- No atoms are lost or gained. The same atoms are just used to make different molecules.
- Therefore, Total Mass of Reactants = Total Mass of Products.
यह नियम क्या है?
द्रव्यमान के संरक्षण का नियम (Law of Conservation of Mass) एक बहुत Simple नियम बताता है:
न तो द्रव्यमान(Mass) बनाया जा सकता है ; और न ही नष्ट किया जा सकता है।
इसका मतलब है कि किसी भी बदलाव में—चाहे वह physical हो (जैसे बर्फ पिघलना) या chemical हो (जैसे लकड़ी जलना)—शामिल सभी पदार्थों का कुल द्रव्यमान (total mass) बदलाव से पहले और बाद में एक समान रहता है।
- Matter का आकार, shape, या volume बदल सकता है।
- लेकिन कुल द्रव्यमान हमेशा constant रहता है।
वैज्ञानिक: एंटोनी लवॉइजियर
यह वह scientist हैं जिन्होंने 18वीं सदी में इस नियम को स्पष्ट किया। उन्हें “आधुनिक रसायन विज्ञान का जनक” कहा जाता है।
उदाहरण (Examples)
उदाहरण 1: बर्फ का पिघलना (Physical Change)
- आप क्या करते हैं: एक glass में 30 grams बर्फ और 50 grams पानी मिलाइए।
- पिघलने से पहले mass: 30 g (बर्फ) + 50 g (पानी) = 80 grams
- क्या होता है: बर्फ पिघलकर पानी बन जाती है।
- पिघलने के बाद mass: glass में कुल पानी = 80 grams
निष्कर्ष: बदलाव से पहले और बाद में mass एक जैसी है। Mass संरक्षित (conserved) रही।
उदाहरण 2: लकड़ी का जलना (Chemical Change)
- आप क्या देखते हैं: लकड़ी जलने पर सिर्फ थोड़ी सी राख बचती है। ऐसा लगता है mass कम हो गई।
- वास्तव में क्या होता है:
- लकड़ी हवा से oxygen के साथ reaction करती है।
- जली हुई लकड़ी (राख) का mass कम है, लेकिन गायब mass गायब नहीं हुई है!
- यह carbon dioxide (CO₂), carbon monoxide (CO), और water vapour जैसी gases के रूप में हवा में मिल गई है।
- जलने से पहले mass = लकड़ी का mass + हवा से ली गई oxygen का mass
- जलने के बाद mass = राख का mass + बनी gases का mass (CO₂, CO, आदि)
निष्कर्ष: अगर आप सभी पदार्थों (राख और gases दोनों) को इकट्ठा करके तौल सकें, तो कुल mass लकड़ी और oxygen के पहले के mass के बराबर होगी।
उदाहरण 3: मैग्नीशियम का जलना (Chemical Reaction)
- अभिक्रिया (Reaction): मैग्नीशियम + ऑक्सीजन → मैग्नीशियम ऑक्साइड
- अभिकारकों का mass (Reactants): 48 g मैग्नीशियम + ? g ऑक्सीजन
- उत्पाद का mass (Product): 80 g मैग्नीशियम ऑक्साइड
- ऑक्सीजन का mass पता करने के लिए: 80 g (उत्पाद) – 48 g (मैग्नीशियम) = 32 g ऑक्सीजन।
- इसलिए, 48 g + 32 g = 80 g। अभिकारकों का कुल mass उत्पाद के कुल mass के बराबर है।
Chemical Reaction का मुख्य विचार:
- अभिकारक (reactants) टूटकर atoms में बदल जाते हैं।
- यह atoms फिर rearrange होकर नए उत्पाद (products) बनाते हैं।
- कोई atoms खोती या बनती नहीं है। एक ही atoms अलग molecules बनाने के लिए इस्तेमाल होते हैं।
- इसलिए, अभिकारकों का कुल द्रव्यमान = उत्पादों का कुल द्रव्यमान।
Of course! Here is a simple summary of the chapter’s main points.
Chapter Summary
Let’s quickly revise everything we learned in this chapter.
1. What is Matter?
- Matter is anything that has mass and occupies space.
- It exists in three main states: Solid, Liquid, and Gas.
2. States of Matter & Their Properties:
- Solids: Have a fixed shape and a fixed volume.
- Liquids: Have a fixed volume but no fixed shape. They take the shape of their container.
- Gases: Have no fixed shape and no fixed volume. They fill their entire container.
3. Kinetic Molecular Theory:
- This theory explains why matter has different states.
- It says that all matter is made of very tiny particles (molecules) that are always moving.
- This movement gives them energy called kinetic energy.
- There is a force of attraction between these particles.
- There is space between these particles.
4. What Decides the State?
- The state of matter (solid, liquid, gas) depends on two things:
- The strength of the force between the particles.
- The amount of space between the particles.
5. Law of Conservation of Mass:
- This is a very important law.
- It states that mass can neither be created nor destroyed.
- In any physical change (like melting ice) or chemical change (like burning wood), the total mass always remains the same.
- In a chemical reaction: Total mass of reactants = Total mass of products.
चलिए इस chapter की सभी मुख्य बातों को quickly revise करते हैं।
1. Matter क्या है?
- Matter वह सब कुछ है जिसका mass (द्रव्यमान) होता है और जो space (जगह) घेरता है।
- यह तीन main states में मिलता है: Solid, Liquid, और Gas।
2. States of Matter और उनके गुण:
- Solids: इनका एक fixed shape और एक fixed volume होता है।
- Liquids: इनका एक fixed volume होता है लेकिन कोई fixed shape नहीं होता। ये अपने container का shape ले लेते हैं।
- Gases: इनका ना कोई fixed shape होता है ना fixed volume। ये अपने पूरे container को भर देती हैं।
3. Kinetic Molecular Theory:
- यह theory समझाती है कि matter के अलग-अलग states क्यों होते हैं।
- यह कहती है कि सारा matter बहुत छोटे particles (molecules) से बना है जो हमेशा move करते रहते हैं।
- इस movement से उन्हें kinetic energy नामक energy मिलती है।
- इन particles के बीच एक आकर्षण बल (force of attraction) होता है।
- इन particles के बीच space होता है।
4. State क्या तय करता है?
- Matter की state (solid, liquid, gas) दो चीज़ों पर निर्भर करती है:
- Particles के बीच के बल की strength।
- Particles के बीच के space की मात्रा।
5. द्रव्यमान के संरक्षण का नियम (Law of Conservation of Mass):
- यह एक बहुत important law है।
- यह बताती है कि न तो mass बनाया जा सकता है और न ही नष्ट किया जा सकता है।
- किसी भी physical change (जैसे बर्फ पिघलना) या chemical change (जैसे लकड़ी जलना) में, कुल mass हमेशा एक जैसी रहती है।
- एक chemical reaction में: अभिकारकों का कुल mass = उत्पादों का कुल mass।
Exercise – Question & Answers
Reference Exercise Questions and Answers of VIVA Publication
A. Fill in the blanks.
- The intermolecular attraction is weaker in gases compared to liquids.
- Explanation: In gases, the particles are far apart, so the force of attraction between them is very weak.
- The kinetic energy of molecules increases as temperature increases.
- Explanation: When you heat something, you give its particles more energy, making them move faster.
- Liquids have a fixed volume but do not have a fixed shape.
- Explanation: A liquid will always take the shape of its container, but the amount of liquid (its volume) stays the same.
- Change in temperature results in change of state of matter.
- Explanation: Heating or cooling a substance can make it change from solid to liquid, liquid to gas, etc.
- The intermolecular spaces are maximum in gases.
- Explanation: Gas particles are spread far apart from each other, with a lot of empty space between them.
B. State whether the following statements are true (T) or false (F).
- Brownian movement is maximum in solids.
- Answer: F (False)
- Explanation: Brownian movement is maximum in gases because their particles move freely and randomly. In solids, particles only vibrate in place.
- The molecules of solids only vibrate at their fixed positions.
- Answer: T (True)
- Explanation: The molecules in a solid are held in place by strong forces, so they cannot move around and can only vibrate.
- The process of converting ice to water is called solidification.
- Answer: F (False)
- Explanation: The process of converting ice to water is called melting or fusion. Solidification is the opposite process, where a liquid turns into a solid.
- The mass of wood and mass of ash after burning remains the same.
- Answer: F (False)
- Explanation: The mass of the ash is less than the mass of the wood because the carbon in the wood combines with oxygen from the air to form gases like carbon dioxide, which escape into the atmosphere.
- Barium chloride is safe to use with bare hands.
- Answer: F (False)
- Explanation: The chapter specifically states that “Barium chloride is a toxic chemical and direct contact with barium chloride should be avoided.”
C. Write down the changes in kinetic energy, intermolecular attraction and intermolecular spaces that will occur in the following.
- When water is frozen to ice
- Kinetic Energy: Decreases
- Intermolecular Attraction: Increases
- Intermolecular Spaces: Decreases
- Explanation: When water is frozen, energy is removed. The particles slow down, come closer together, and the forces between them become stronger, forming a solid structure.
- When gas is compressed to liquid
- Kinetic Energy: Decreases
- Intermolecular Attraction: Increases
- Intermolecular Spaces: Decreases
- Explanation: Compressing a gas and cooling it removes energy from the particles. They slow down, get closer together, and the forces of attraction become strong enough to hold them together as a liquid.
- When camphor changes to gaseous state
- Kinetic Energy: Increases
- Intermolecular Attraction: Decreases
- Intermolecular Spaces: Increases
- Explanation: This process is called sublimation. The solid camphor particles gain energy, start moving very fast, overcome the forces of attraction, and spread far apart to become a gas.
D. Choose the correct answer.
- Which is a property of solids?
(a) Large intermolecular spaces
(b) Compressible
(c) High kinetic energy
(d) Rigid- Explanation: Solids are rigid, meaning they have a fixed shape and are hard to change. The other options are properties of gases.
- Which is a property of liquids?
(a) Fixed shape
(b) Very low intermolecular attraction
(c) Fixed volume
(d) Compressible- Explanation: Liquids have a fixed volume but take the shape of their container. They are not easily compressible.
- Which is a property of gases?
(a) Fixed shape
(b) Fixed volume
(c) Rigid
(d) Lowest force of attraction- Explanation: The particles in a gas are very far apart, so the intermolecular force of attraction is the lowest among the three states of matter.
- Which of the following is the process by which gas changes to liquid?
(a) Solidification
(b) Sublimation
(c) Condensation
(d) Vaporisation- Explanation: Condensation is the process where a gas turns into a liquid, like when water vapour forms dew.
- What is the mass of product(s), if the mass of reactants is 10 g and 40 g each?
(a) 10 g
(b) 40 g
(c) 50 g
(d) 60 g- Explanation: According to the Law of Conservation of Mass, the total mass of the reactants (10 g + 40 g = 50 g) is equal to the total mass of the products.
E. Match the columns.
| Column A | Column B |
|---|---|
| 1. Change of phase | (a) Loosely held molecules |
| 2. Solids | (b) Change in kinetic energy |
| 3. Gases | (c) Naphthalene |
| 4. Liquids | (d) Tightly packed molecules |
| 5. Sublimation | (e) Shape of container |
Answer:
| Column A | Column B |
|---|---|
| 1. Change of phase | (b) Change in kinetic energy |
| 2. Solids | (d) Tightly packed molecules |
| 3. Gases | (a) Loosely held molecules |
| 4. Liquids | (e) Shape of container |
| 5. Sublimation | (c) Naphthalene |
Explanation of Matches:
- Change of phase happens when particles gain or lose kinetic energy, changing their motion and arrangement.
- Solids have molecules that are tightly packed together in a fixed structure.
- Gases have molecules that are very far apart and are loosely held, moving freely.
- Liquids take the shape of their container because they can flow.
- Sublimation is when a solid turns directly into a gas. Naphthalene balls are a common example of this.
F. Give reasons for the following statements.
- The particles in a solid remain in fixed positions.
- Reason: In solids, the intermolecular force of attraction is the strongest and the intermolecular space is negligible. The molecules are arranged in a well-defined order and the kinetic energy is not enough to break the strong force, so they only vibrate at their fixed positions.
- Increase in temperature causes increase in kinetic energy.
- Reason: The kinetic molecular theory states that particles possess kinetic energy due to their constant motion. As temperature increases, the particles gain energy and move faster, which means their kinetic energy increases.
- The intermolecular spaces in liquids is more than that in solids.
- Reason: The molecules in liquids are less closely packed compared to solids. Therefore, the intermolecular space in liquids is more than in solids, which allows the molecules to move from one position to another.
- The mass of reactants is equal to the mass of products.
- Reason: This is due to the Law of Conservation of Mass, which states that mass can neither be created nor destroyed. The atoms in the reactants are the same as the ones present in the products, only rearranged, thus conserving the total mass.
- Liquids evaporate when heated.
- Reason: When a liquid is heated, its molecules gain kinetic energy. This energy enables them to overcome the intermolecular force of attraction, and they escape from the liquid’s surface, changing into vapour.
H. Differentiate between the following. Give examples wherever applicable.
1. Solids, liquids and gases
| Property | Solids | Liquids | Gases |
|---|---|---|---|
| Shape & Volume | Have fixed shape and volume. | Have fixed volume but no fixed shape. They take the shape of the container. | Have no fixed shape or volume. They take the shape and volume of the container. |
| Intermolecular Force | Strongest | Weaker than solids, but stronger than gases. | Negligible (weakest) |
| Intermolecular Space | Negligible (very less) | More than solids | Maximum |
| Compressibility | Incompressible | Incompressible | Highly compressible |
| Movement of Particles | Particles only vibrate at fixed positions. | Particles can move and slide past each other. | Particles move randomly and freely in all directions. |
| Example | Wood, ice | Milk, water | Oxygen, smoke |
2. Conservation of mass during a physical change and conservation of mass during a chemical change
| Aspect | Conservation of Mass in a Physical Change | Conservation of Mass in a Chemical Change |
|---|---|---|
| Definition | The total mass of the substance remains the same before and after a change in its physical state. | The total mass of the reactants is equal to the total mass of the products formed. |
| Nature of Change | Involves a change in physical properties like size, shape, or state. No new substance is formed. | Involves the formation of new substances with different properties. |
| What happens to particles? | The molecules remain the same; only their arrangement, motion, or space changes. | The atoms of the reactants rearrange themselves to form molecules of new products. |
| Example | Melting 30 g of ice in 50 g of water gives 80 g of water. | Burning magnesium (48g) in oxygen (32g) produces 80g of magnesium oxide. |