Chemical Reactions and Equations: Class 10 Science Chapter 1 Hinglish mein

Science · Hinglish notes, simulations aur practice · Official NCERT chapter PDF ↗

Published 12 Oct 2026 · Updated 12 Oct 2026

90 min
1 simulation
31 practice questions
26 MCQs

Is chapter mein aap kya seekhenge

Jo dikhta hai usse chemical reaction pehchaano: naya colour, gas, temperature ka change ya naya solid
Word equations aur chemical equations likho, aur atoms gin kar unhe balance karo taaki mass conserve rahe
Chemical equation ko state symbols aur arrow par likhi conditions ke saath poora karo
Reactions ko combination, decomposition, displacement ya double displacement mein, aur exothermic ya endothermic mein classify karo
Kaunsa reactant oxygen ya hydrogen leta hai ya deta hai, yeh track karke oxidised aur reduced substance pehchaano
Corrosion aur rancidity ko oxidation ke roz ke effects ki tarah samjhao, aur yeh bhi ki hum inhe dheema kaise karte hain

NCERT Science Class 10, Chapter 1, pp. 1–16 par based original companion text. Yeh NCERT se juda nahi hai aur NCERT ne ise endorse nahi kiya hai.

Chemical reaction pehchaanna

Raat ko garam doodh mein ek chammach dahi milao aur subah tak dahi jam jaata hai. Monsoon bhar bahar chhodi cycle ki chain par orange-brown parat chadh jaati hai. Dosa batter phool jaata hai aur khatta ho jaata hai, aur kata hua apple kuch hi minutes mein brown ho jaata hai. Har baar jo cheez shuru mein thi, woh kisi aisi cheez mein badal gayi jiska taste, colour ya texture alag hai.

Pichhli classes mein tumne changes ko do tarah mein baanta tha. Physical change mein, jaise ghee pighalna ya sugar ghulna, koi naya substance nahi banta. Chemical change mein kam se kam ek naya substance banta hai, jiske apne properties hote hain. Chemists chemical change ko chemical reaction kehte hain. To asli sawaal yeh hai: tumhari aankhein, naak aur ungliyan tumhe kya bata sakti hain? Teen activities saboot dengi.

Activity 1.1NCERT Activity 1.1 · p. 1

Ek ribbon jo chamakdaar roshni ke saath jalta hai

Tumhe chahiye

magnesium ribbon ki 3 cm lambi patti
sandpaper
ek chimta (tongs)
ek spirit lamp ya burner
ek china dish ya steel ka dhakkan

Pehle guess karo

Tumhe kya lagta hai, ribbon jalne ke baad kya bachega?

Kuch nahi: metal jal kar hawa mein ud jaata haiEk white powderPighle metal ka ek chamakdaar daanaKaali kaalikh, jaise candle se aati hai

Ribbon ko sandpaper se tab tak ragdo jab tak woh chamakdaar aur silvery na ho jaaye.
Ek end ko chimte se pakdo aur doosre end ko flame mein rakho, haath poora failaakar.
Jaise hi woh jalne lage, use dish ke upar pakdo taaki raakh usmein gire. Flame ko sirf aankh ke kone se dekho.
Dish mein bache powder ko bina jale ribbon ke tukde se compare karo.

Table 1.1

Property	Ribbon	Kya bacha
Colour
Chamak
Mudta hai ya bhurbhura hai?

Tumhari entries apne aap save hoti hain.

Activity 1.2NCERT Activity 1.2 · p. 2

Do saaf liquids, ek surprise

Tumhe chahiye

lead nitrate ka solution
potassium iodide ka solution
ek white spotting tile ya ek chhoti test tube
do droppers

Pehle guess karo

Dono solutions colourless hain. Jahan woh milenge, wahan tumhe kya dikhega?

Kuch nahi: woh colourless hi rehte hainEk chamakdaar yellow solidMixture ubalne lagta haiEk gehra blue colour

Tile ke ek gaddhe mein lead nitrate solution ki do boondein daalo.
Potassium iodide solution ki do boondein daalo aur dhyaan se dekho.
Colour note karo, aur yeh bhi ki mixture saaf rehta hai ya nahi.

Activity 1.3NCERT Activity 1.3 · p. 2

Zinc se fizz aur garmi

Tumhe chahiye

zinc ke 4–5 granules
dilute hydrochloric acid ya dilute sulphuric acid
stand mein ek test tube
ek dropper

Pehle guess karo

Acid daalne ke baad tumhe kya lagta hai, tube ka neeche ka hissa chhoone mein kaisa lagega?

Pehle se garamPehle se thandaBilkul pehle jaisaChikna

Zinc granules ko test tube mein daalo.
Dropper se dilute acid tab tak daalo jab tak granules bas dhak na jaayein.
Ek minute tak zinc ki surface ko dekho.
Tube ke neeche wale hisse ke chaaron taraf ungliyan halke se lapeto.

Table 1.2

Kya check karna hai	Maine kya dekha
Zinc ke aas-paas
Tube ka temperature

Tumhari entries apne aap save hoti hain.

Teeno activities ko saath rakho to tumhare paas ek checklist ban jaati hai. Reaction shayad ho raha hai jab tum inmein se ek ya zyada cheezein notice karo:

colour ka change, jaise do colourless liquids se bana yellow
gas ka nikalna, jaise zinc par hydrogen ke bubbles
temperature ka change, jaise garam test tube
state ka change, jaise liquid mein naya solid dikhna, ya metal ka bhurbhura hokar powder ban jaana

5/5Liquid mein naya solid banta hai.

Fig. 1.1Chaar clues jo batate hain ki chemical reaction ho raha ho sakta hai.

Chaar test tubes ek line mein khadi hain, har ek aadhi saaf liquid se bhari hai. Pehle step mein abhi kuch nahi badla. Colour step mein pehli tube ka liquid yellow ho jaata hai. Gas step mein doosri tube mein bhi bubbles uthte hain. Warmth step mein teesri tube ke paas rakha thermometer zyada reading dikhata hai. Solid step mein chauthi tube ke neeche naye solid ki ek layer baith jaati hai, aur ab chaaron clues ek saath dikhte hain.

Inhe clues samjho, proof nahi. Paani ubalne par bubbles banata hai aur barf pighalne par state badalti hai, phir bhi kuch naya nahi banta: shuru se aakhir tak woh paani hi hai. Asli test hamesha yeh hai ki koi naya substance bana ya nahi. Simulation dikhata hai ki sirf state ka change tumhe kaise dhokha de sakta hai.

SimulationBarf se steam: phir bhi paani

Paani ke particles ka ek band container, saath mein ek thermometer aur minus 20 se 120 degrees Celsius tak ka temperature slider. 0 °C se neeche particles barf ki tarah ek regular pattern mein sate hue baithe hain; 0 aur 100 °C ke beech woh liquid water ki tarah ek doosre ke paas se phisalte hain; 100 °C se upar woh alag-alag udkar steam ki tarah poore container mein bhar jaate hain. Ek label state ka naam batata hai. Har state mein particles wahi paani ke particles hain; sirf unki doori aur motion badalte hain.

Fig. 1.2Barf se steam tak paani ke particles. Play dabao, phir temperature slider drag karo.

Try karo

−10 °C se shuru karo aur dheere-dheere 110 °C tak drag karo. Kya koi particle kabhi kisi alag tarah ke particle mein badalta hai?
Slider ko 100 °C se thoda upar rok kar rakho. Paani mein bubbles ban rahe hain, lekin kya kuch naya ban raha hai?
Wapas −10 °C tak drag karo. Tumhe phir se barf milti hai. Kya tum bina jala magnesium ribbon itni aasani se wapas pa sakte ho?

1.1 Chemical Equations

Agar lab notebook aise sentences se bhari ho, jaise “magnesium hawa mein jalta hai aur oxygen se judkar magnesium oxide ban jaata hai”, to use likhna bhi slow hoga aur padhna bhi. Isliye chemistry ek shorthand use karti hai, jo do stages mein banta hai. Pehle stage mein naam rehte hain lekin grammar hata dete hain, aur hamein milta hai ek word equation:

word equation

\begin{aligned} magnesium \\ + oxygen \\ \to magnesium oxide \end{aligned}

(1.1)

Arrow ke left mein jo kuch hai, woh use ho jaata hai: yeh reactants hain. Right mein jo kuch hai, woh naya bana hai: yeh products hain. Plus sign ka matlab bas “aur” hai. Arrow batata hai ki change kis taraf chalta hai, isliye use “react karke dete hain” padho. Yeh equals sign nahi hai, kyunki dono sides alag substances hain.

Definition

Reactant

Aisa substance jo chemical reaction mein use hota hai aur badal jaata hai; ise arrow ke left mein likhte hain.

ExampleRibbon jalne par magnesium aur oxygen.

Definition

Product

Chemical reaction mein bana naya substance; ise arrow ke right mein likhte hain.

ExampleMagnesium oxide, yaani white raakh.

1.1.1 Chemical Equation Likhna

Naam phir bhi lambe hain, aur woh yeh nahi batate ki kitne atoms hissa lete hain. Isliye hum har naam ki jagah uska chemical formula likhte hain: magnesium ke liye $M g$ , oxygen gas ke liye $O_{2}$ (jo do-atom wale molecules se bani hai) aur magnesium oxide ke liye $M g O$ . Jo milta hai, woh hai ek chemical equation.

skeletal equation

M g + O_{2} \overset{}{\to} M g O

(1.2)

Ab atoms gino. Left side par ek magnesium atom aur do oxygen atoms hain; right side par dono ka ek-ek. Lagta hai ek oxygen atom gayab ho gaya, aur aisa ho nahi sakta. Aisi equation, jismein formulae sahi hain lekin atoms ki ginti barabar nahi, skeletal equation kehlaati hai. Ise ek pehla draft samjho jise abhi balance karna baaki hai.

Definition

Chemical equation

Chemical formulae se reaction likhne ka chhota tareeka: left mein reactants, phir arrow, aur right mein products.

Example $M g + O_{2} \overset{}{\to} M g O$ (abhi balance karna baaki hai).

1.1.2 Balanced Chemical Equations

Atoms ki ginti match kyun honi chahiye? Atoms ko building blocks ki tarah socho. Reaction blocks ko alag karta hai aur unhe naye tareekon se jodta hai, lekin kabhi naya block nahi banata aur na hi kisi block ko khatam karta hai. Agar tum ek sealed flask ko uske andar reaction hone se pehle aur baad mein tolo, to reading nahi badalti.

LawLaw of conservation of mass

Chemical reaction mein total mass same rehta hai: products milkar thik utne hi bhaari hote hain jitne woh reactants jinse woh bane.

To sahi equation mein har element ke atoms dono sides par barabar hone chahiye. Aisi equation ko balanced equation kehte hain. Kuch equations likhte hi balanced hoti hain. Activity 1.3 mein zinc aur sulphuric acid yeh dete hain:

zinc aur sulphuric acid

\begin{aligned} Z n + H_{2} S O_{4} \\ \overset{}{\to} Z n S O_{4} + H_{2} \end{aligned}

(1.3)

Ginti karo: zinc 1 aur 1, hydrogen 2 aur 2, sulphur 1 aur 1, oxygen 4 aur 4. Har element match karta hai, isliye kuch badalne ki zaroorat nahi. Magnesium wali equation alag hai. Fig. 1.3 ise particle picture se thik karta hai.

3/3Do Mg: har atom balance.

Fig. 1.3Poore particles jodkar

M g + O_{2} \overset{}{\to} M g O

ko balance karna.

Atoms ko label wale circles ki tarah dikhaya gaya hai: magnesium ke liye Mg aur oxygen ke liye O, aur oxygen molecule do jude hue O circles hai. Pehle step mein ek Mg atom aur ek oxygen molecule ek MgO unit dete hain, aur tallies dikhati hain ki left mein 2 oxygen atoms hain lekin right mein sirf 1. Doosre step mein right par ek aur MgO unit joda jaata hai, to oxygen ab match karta hai lekin magnesium left mein 1 aur right mein 2 hai. Teesre step mein left par ek aur Mg atom joda jaata hai aur dono tallies match karti hain, har side par do Mg aur do O.

Definition

Balanced chemical equation

Aisi chemical equation jismein har element ke atoms reactant side par utne hi hon jitne product side par.

Example $2 M g + O_{2} \overset{}{\to} 2 M g O$

Balance karne ka ek golden rule hai: sirf formulae ke aage likhe numbers badlo, jinhe coefficients kehte hain. Coefficient batata hai ki tum kitne molecules (ya formula units) le rahe ho. Formula ke andar ke chhote numbers, yaani subscripts, khud substance ka hissa hain. $H_{2} O$ ko $H_{2} O_{2}$ bana do to tumne hydrogen peroxide likh diya, jo ek antiseptic aur bleach hai, paani nahi (Fig. 1.4).

3/3Badla hua subscript: naya substance.

Fig. 1.4Coefficient molecules ginta hai; subscript molecule hi badal deta hai.

Molecules ko jude hue circles ki tarah dikhaya gaya hai, oxygen ke liye bada circle O aur hydrogen ke liye chhote circles H. Pehle step mein paani ka ek molecule dikhaya gaya hai. Doosre step mein 2 ka coefficient do alag water molecules deta hai, jo phir bhi paani hain. Teesre step mein iske bajaay subscript badal diya gaya hai, aur ek aisa molecule milta hai jismein do oxygen aur do hydrogen atoms ek chain mein hain: hydrogen peroxide, ek alag substance, jis par cross laga hai kyunki balance karte samay aisa karna allowed nahi hai.

Hit-and-trial se balance karna

Is saal tumhe milne wali zyadatar equations ek dhyaan se kiye gaye try-and-check tareeke se balance ho sakti hain, jise hit-and-trial method kehte hain:

Sahi formulae ke saath skeletal equation likho, phir har formula ko sealed maano: ab se tum sirf uske aage numbers laga sakte ho.
Har side par har element ke atoms gino.
Sabse bada formula chuno (jismein sabse zyada atoms hon) aur uske andar woh element jo sabse zyada aata hai. Pehle us element ko barabar karo.
Baaki elements ko ek-ek karke balance karo. Jo elements akele khade hain, jaise $O_{2}$ , $H_{2}$ ya $F e$ , unhe aakhir ke liye chhodo.
Har atom dobara gino. Agar saare coefficients mein koi common factor hai, to usse divide karke sabse chhote whole numbers pao.

Example 1.1

LPG cylinder ki gas ko balance karna

Cooking gas (LPG) butane aur propane, $C_{3} H_{8}$ , ka mixture hai. Propane oxygen mein jalkar carbon dioxide aur paani deti hai. Skeletal equation ko balance karo:

\begin{aligned} C_{3} H_{8} + O_{2} \\ \overset{}{\to} C O_{2} + H_{2} O \end{aligned}

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Example 1.2

Odd–even trick: hawa mein aluminium

Nayi aluminium kadhai par jald hi aluminium oxide ki ek patli, dhundhli parat chadh jaati hai, jo neeche ke metal ko bachaati hai. Iske banne ki equation balance karo:

\begin{aligned} A l + O_{2} \\ \overset{}{\to} A l_{2} O_{3} \end{aligned}

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Example 1.3

Poore ion ko ek unit maanna

Water works mein gande, mitti wale paani mein aluminium sulphate daala jaata hai, jo fitkari (alum) ka main hissa hai. Sodium hydroxide jaise alkali ke saath yeh chipchipa aluminium hydroxide banata hai, jo mitti ko neeche kheench leta hai. Balance karo:

\begin{aligned} A l_{2} (S O_{4})_{3} \\ + N a O H \\ \overset{}{\to} A l (O H)_{3} \\ + N a_{2} S O_{4} \end{aligned}

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Neeche diye balancer par apni pasand ki reactions ke saath yeh tareeka practice karo. Yeh tumhare liye atoms ginta hai, taaki tum strategy par dhyaan de sako.

InteractiveEquation balancer

Ek interactive balancer. Ek menu nau skeletal equations mein se ek chunta hai, oxygen mein jalte calcium se lekar oxygen mein jalte ammonia tak, har ek ke saath uska reaction type. Har formula ke paas ek minus aur ek plus button hai jo uska coefficient 1 se 15 tak badalta hai. Ek table har element ko left aur right ke atom count ke saath dikhata hai; match hone par tick aur na hone par cross lagta hai. Ek status line batati hai ki equation balanced hai ya nahi, aur coefficients sabse chhote whole numbers hain ya nahi. Hint button batata hai ki aage kaunsa element thik karna hai, Reset har coefficient ko wapas 1 kar deta hai, aur Show answer balanced coefficients bhar deta hai.

Fig. 1.5Ek reaction chuno, phir har formula ke neeche − aur + tab tak dabao jab tak har element balance na ho jaaye.

Physical states likhna

Balanced equation bhi ek kaam ki baat chhupa leti hai: har substance solid hai, liquid hai, gas hai ya solution? Yeh hum har formula ke baad brackets mein ek state symbol lagakar dikhate hain.

Table 1.3State symbols

Symbol	Matlab	Example
(s)	solid	zinc ke granules, $Z n (s)$
(l)	liquid	paani, $H_{2} O (l)$
(g)	gas, ya steam jaisi vapour	hydrogen, $H_{2} (g)$
(aq)	aqueous: paani mein ghula hua	dilute acid, $H_{2} S O_{4} (a q)$

State symbols ke saath (1.3) ka zinc reaction aisa ban jaata hai:

state symbols ke saath

\begin{aligned} Z n (s) \\ + H_{2} S O_{4} (a q) \\ \overset{}{\to} Z n S O_{4} (a q) \\ + H_{2} (g) \end{aligned}

Equations aksar bina state symbols ke likhi jaati hain. Jab woh maayne rakhte hon tab unhe lagao, jaise jab paani steam ki tarah react kare ya solution ke andar solid bane, aur jab bhi sawaal mein unhe maanga jaaye.

Reaction ko jo conditions chahiye, woh arrow par likhi jaati hain: heat, light, high pressure, ya ek catalyst, yaani aisa substance jo reaction ko tez karta hai lekin khud use nahi hota. First-aid box ka hydrogen peroxide apne aap dheere-dheere tootta hai, lekin chutki bhar manganese dioxide daalne par woh tezi se fizz karke oxygen chhodta hai:

arrow par catalyst

\begin{aligned} 2 H_{2} O_{2} (a q) \\ \overset{M n O_{2}}{\to} 2 H_{2} O (l) \\ + O_{2} (g) \end{aligned}

Baking soda garam karne par carbon dioxide aur steam chhodta hai, yeh ek wajah hai ki oven mein cake phoolta hai:

arrow par heat

\begin{aligned} 2 N a H C O_{3} (s) \\ \overset{heat}{\to} N a_{2} C O_{3} (s) \\ + H_{2} O (g) + C O_{2} (g) \end{aligned}

Example 1.4

Sentence se poori equation tak

Washing soda (sodium carbonate) ka solution dilute hydrochloric acid se react karke sodium chloride solution, paani aur carbon dioxide gas deta hai. State symbols ke saath balanced equation likho.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Quick check

4 mein se 1

Magnesium equation balance karo:

M g

O_{2}

→

M g O

Answer dekho

Answer (1) 2, (2) 2

Do MgO units ko do oxygen atoms chahiye, jo ek

O_{2}

de deta hai. Unhe do magnesium atoms bhi chahiye, isliye answer hai

2 M g + O_{2} \overset{}{\to} 2 M g O

Practice · 3 questions

Ruko aur practice karo 1: answers ke saath

Short answerEasyNCERT in-text Questions p. 6, Q1
Purane packet ka magnesium ribbon dhundhla grey dikhta hai. Jalaane se pehle ek student use sandpaper se tab tak ragadta hai jab tak woh chamakne na lage. Kyun?
Solution dikhao
Samay ke saath magnesium hawa ki oxygen (aur carbon dioxide) se react karta hai aur us par magnesium oxide ki patli parat chadh jaati hai. Yeh parat jalti nahi aur hawa ko metal tak pahunchne nahi deti, isliye ribbon mushkil se jalta hai. Sandpaper se ragadne par taaza metal bahar aata hai, jo aasani se aag pakad leta hai.
2
Short answerMediumNCERT in-text Questions p. 6, Q2
Har reaction ki balanced equation likho.
1. Sulphur dioxide + oxygen → sulphur trioxide
  Solution dikhao
  $2 S O_{2}$ + $O_{2}$ → $2 S O_{3}$
  Sulphur 2 aur 2, oxygen 4 + 2 = 6 aur 6.
2. Iron(III) oxide + hydrogen → iron + paani
  Solution dikhao
  $F e_{2} O_{3}$ + $3 H_{2}$ → $2 F e$ + $3 H_{2} O$
  Iron 2 aur 2, oxygen 3 aur 3, hydrogen 6 aur 6.
3. Magnesium + nitrogen → magnesium nitride ( $M g_{3} N_{2}$ )
  Solution dikhao
  $3 M g$ + $N_{2}$ → $M g_{3} N_{2}$
  $M g_{3} N_{2}$ ke teen magnesium atoms ke liye teen magnesium atoms chahiye; nitrogen pehle se 2 aur 2 hai.
3
Short answerMediumNCERT in-text Questions p. 6, Q3
Har balanced equation state symbols ke saath likho.
1. Lead nitrate solution ko sodium sulphate solution mein daala jaata hai. White lead sulphate neeche baith jaata hai, aur sodium nitrate ghula hua reh jaata hai.
  Solution dikhao
  $P b (N O_{3})_{2} (a q)$ + $N a_{2} S O_{4} (a q)$ → $P b S O_{4} (s)$ + $2 N a N O_{3} (a q)$
  Left ke do nitrate groups ke liye do $N a N O_{3}$ chahiye, jo dono sodium atoms ko bhi use kar lete hain.
2. Dilute nitric acid potassium hydroxide solution ko poori tarah neutralise karta hai. Products hain paani aur ghula hua potassium nitrate.
  Solution dikhao
  $K O H (a q)$ + $H N O_{3} (a q)$ → $K N O_{3} (a q)$ + $H_{2} O (l)$
  Pehle se balanced: K, N, H aur O, sab match karte hain.

1.2 Chemical Reactions ke Types

Magnesium ribbon ko yaad karo. Ribbon ka har magnesium atom white raakh mein abhi bhi maujood hai; usne bas apne purane padosiyon ko chhoda hai aur oxygen atoms ko naye partners bana liya hai. Har reaction bas yahi karta hai. Kuch bonds tootte hain, kuch naye bante hain, aur wahi atoms naye substances ki tarah arrange ho jaate hain. Atoms ek doosre ko kaise pakad kar rakhte hain, yeh Chapters 3 aur 4 ka topic hai.

Reactions kuch common patterns mein aate hain. Pattern pehchaan lo to products predict karna aur equation likhna aasaan ho jaata hai. Fig. 1.6 inmein se chaar dikhata hai, jahan shapes atoms ya atoms ke groups ki jagah hain.

1/5Atoms ke rearrange hone ke chaar tareeke.

Fig. 1.6Chemical reaction ke chaar patterns.

Chaar rows ek circle A, ek square B, ek triangle C aur ek diamond D se reaction patterns dikhati hain. Combination: A aur B judkar AB bante hain. Decomposition: AB tootkar A aur B ban jaata hai. Displacement: A, BC se milta hai aur B ki jagah le leta hai, jisse AC aur ek free B milta hai. Double displacement: AB aur CD partners badalkar AD aur CB dete hain. Pehle step mein chaaron rows dikhti hain; har agla step ek row ko highlight karta hai aur baaki teen ko dhundhla kar deta hai.

1.2.1 Combination Reaction

Activity 1.4NCERT Activity 1.4 · p. 6

Quicklime aur paani ka milan

Tumhe chahiye

quicklime (calcium oxide) ke do-teen chhote tukde
ek glass beaker
paani
ek thermometer
ek glass rod

Pehle guess karo

Quicklime mein paani daalne ke baad thermometer kya dikhayega?

Temperature tezi se girta haiTemperature mushkil se badalta haiThermometer paste ke andar padh hi nahi saktaTemperature kaafi badh jaata hai

Tukdon ko beaker mein rakho aur thermometer ki reading note karo.
Paani dheere-dheere, thoda-thoda daalo, aur rod se halke se chalate raho.
Thermometer ko mixture mein pakad kar rakho aur teen minute tak har aadhe minute par reading lo.
Dekho ki tukde kis cheez mein badal gaye hain.

Table 1.4

Samay	Temperature (°C)
Paani se pehle
1 minute baad
3 minute baad

Tumhari entries apne aap save hoti hain.

3/3Slaked lime banta hai aur mixture garam ho jaata hai.

Fig. 1.7Quicklime aur paani milkar heat chhodte hain.NCERT Fig. 1.3 · p. 6

Ek beaker mein white tukde hain aur usmein ek thermometer khada hai. Pehle step mein tukde sookhe hain aur thermometer room temperature dikhata hai. Doosre step mein paani daala gaya hai, aur tukdon se chhote bubbles aur hiss shabd upar uthte hain. Teesre step mein beaker mein slaked lime ka doodhiya paste hai, uske upar steam ke chhalle uthte hain aur thermometer ka column kaafi upar chadh gaya hai.

quicklime → slaked lime

\begin{aligned} C a O (s) + H_{2} O (l) \\ \overset{}{\to} C a (O H)_{2} (a q) \\ + heat \end{aligned}

(1.13)

Gino ki kya andar gaya aur kya bahar aaya: do substances andar, sirf ek bahar. Is shape wala koi bhi reaction, jismein kai reactants aur ek hi product ho, combination reaction hai. Reactants elements ho sakte hain, jaise magnesium aur oxygen, ya compounds, jaise quicklime aur paani.

Definition

Combination reaction

Aisa reaction jismein do ya zyada reactants judkar ek hi product banate hain.

ExampleCalcium oxide aur paani milkar calcium hydroxide banate hain.

Tum doosre combination reactions se pehle hi mil chuke ho:

Activity 1.1 ka magnesium ribbon, jahan do elements milkar ek white product banate hain, $2 M g + O_{2} \overset{}{\to} 2 M g O$ , aur khoob heat aur light nikalti hai
angithi (mitti ka chulha) mein dahakta charcoal, $C + O_{2} \overset{}{\to} C O_{2}$
ammonia aur hydrochloric acid ki khuli bottles paas-paas rakhi hon: unki gases hawa mein milti hain aur ammonium chloride ka white dhuan banati hain, $N H_{3} + H C l \overset{}{\to} N H_{4} C l$
ISRO ke sabse bhaari rockets ka upper stage, jahan liquid hydrogen aur liquid oxygen milkar paani banate hain, $2 H_{2} + O_{2} \overset{}{\to} 2 H_{2} O$ , aur woh energy chhodte hain jo rocket ko aage dhakelti hai

Dhyaan do ki heat kitni baar aati hai. Jo reaction apne surroundings ko heat deta hai, woh exothermic reaction hai (exo ka matlab hai bahar). LPG ka jalna (Example 1.1) aisa hi ek reaction hai, aur gas stove ka poora maqsad yahi hai. Kitchen ke kachre ka dheere-dheere sadna bhi ek aur example hai: sardi ki subah compost pit mein khodo to andar garam milta hai.

Definition

Exothermic reaction

Aisa reaction jo products bante samay apne surroundings ko heat deta hai.

ExampleCharcoal ya LPG ka jalna; quicklime aur paani.

Daud ke baad apna maatha chhoo kar dekho. Woh garmi tumhare sharir ke har cell mein chal rahe ek reaction se aati hai. Glucose, jo starch wala khana pachaane par banta hai, saans mein li gayi oxygen ke saath dheere-dheere “jalaya” jaata hai. Yeh controlled jalna, respiration, woh energy chhodta hai jo tumhe zinda aur garam rakhti hai. Chapter 5 ise dhyaan se dekhta hai.

glucose ka respiration

\begin{aligned} C_{6} H_{12} O_{6} (a q) \\ + 6 O_{2} (a q) \\ \overset{}{\to} 6 C O_{2} (a q) \\ + 6 H_{2} O (l) + energy \end{aligned}

(1.18)

1.2.2 Decomposition Reaction

Decomposition ulta chalaya gaya combination hai: ek akela compound tootkar do ya zyada simple substances ban jaata hai. Compound ko todne ka matlab hai bonds todna, aur ismein energy lagti hai, isliye in reactions ko chalte rehne ke liye aam taur par heat, light ya electricity chahiye.

Activity 1.5NCERT Activity 1.5 · p. 8

Hare crystals jo brown ho jaate hain

Tumhe chahiye

spatula ki nok bhar ferrous sulphate crystals (green vitriol)
ek sookhi boiling tube
ek test-tube holder
ek burner

Pehle guess karo

Tez garam karne ke baad solid ka colour kya hoga?

Laal-bhoora (reddish brown)Abhi bhi halka haraChamakdaar blueChamakdaar silver

Sookhi boiling tube mein crystals ka colour note karo.
Tube ko holder se pakdo, uska munh sabse door rakho, aur pehle halke se, phir tez garam karo.
Tube ke upar wale thande hisse aur solid ke colour ko dekho.
Haath se munh ke upar ki hawa ko apni naak ki taraf halke se laao. Tube ko kabhi seedhe mat sungho.

Table 1.5

Stage	Maine kya dekha
Garam karne se pehle
Halka garam karna
Tez garam karna

Tumhari entries apne aap save hoti hain.

ferrous sulphate → ferric oxide

\begin{aligned} 2 F e S O_{4} (s) \\ \overset{heat}{\to} F e_{2} O_{3} (s) \\ + S O_{2} (g) + S O_{3} (g) \end{aligned}

(1.19)

3/3Lead nitrate: nitrogen dioxide ke brown fumes.

Fig. 1.8Do thermal decompositions saath-saath.NCERT Figs. 1.4–1.5 · p. 8

Do boiling tubes do burners ke upar tirchi pakdi hui hain. Left tube mein hare ferrous sulphate crystals hain aur right tube mein white lead nitrate powder. Doosre step mein left tube ke munh ke paas paani ki boondein aur neeche reddish-brown solid dikhta hai, saath mein jalte sulphur ki smell ka label hai. Teesre step mein nitrogen dioxide ke brown fumes right tube mein bhar jaate hain aur uske munh se upar uthte hain, aur uske neeche ek peela sa solid bach jaata hai.

Jis reaction mein ek substance tootkar simple substances mein badal jaata hai, woh decomposition reaction hai. Jab ise heat chalati hai, to hum ise thermal decomposition kehte hain. Industry khaas taur par ek aise reaction par nirbhar hai. Kiln mein garam kiya gaya limestone tootkar quicklime aur carbon dioxide ban jaata hai; Madhya Pradesh mein Katni ke aas-paas ke lime kilns thik yahi karte hain, aur har cement kiln ke andar pehla step bhi yahi reaction hai.

limestone → quicklime

\begin{aligned} C a C O_{3} (s) \\ \overset{heat}{\to} C a O (s) \\ + C O_{2} (g) \end{aligned}

(1.20)

Definition

Decomposition reaction

Aisa reaction jismein ek akela reactant tootkar do ya zyada simple products ban jaata hai.

ExampleLimestone ko garam karne par quicklime aur carbon dioxide milte hain.

lead nitrate

\begin{aligned} 2 P b (N O_{3})_{2} (s) \\ \overset{heat}{\to} 2 P b O (s) \\ + 4 N O_{2} (g) + O_{2} (g) \end{aligned}

(1.21)

Energy dene ka sirf heat hi tareeka nahi hai. Agli do activities electricity aur light use karti hain.

Activity 1.7NCERT Activity 1.7 · p. 9

Battery se paani ko todna

Tumhe chahiye

ek electrolysis vessel jiske base se do electrodes upar aate hain
paani jismein dilute sulphuric acid ki kuch boondein mili hon
do test tubes
ek 9 V battery, ek switch aur wires
lakdi ki teeliyan (splints) aur maachis

Pehle guess karo

Kya dono tubes ek hi rate se gas se bharengi?

Haan, bilkul ek hi rate seSirf ek tube mein gas jama hoti haiEk tube doosri se lagbhag do guna tezi se bharti haiDono mein nahi: paani toota nahi ja sakta

Vessel ko acid mile paani se bharo taaki dono electrodes dhak jaayein.
Dono test tubes ko poora labalab bharo, har ek ko angoothe se band karo, aur unhe paani ke andar electrodes ke upar ulta kar do.
Electrodes ko switch ke through battery se jodo, aur switch on karo.
Jab ek tube lagbhag gas se bhar jaaye, switch off karo aur har tube ko ulta hi rakhte hue bahar nikaalo.
Teacher zyada bhari tube ke munh par jalti teeli laate hain, aur doosri tube mein sulagti teeli.

Table 1.6

Electrode	Gas ka volume (mL)	Teeli (splint) test
− terminal se juda
+ terminal se juda

Tumhari entries apne aap save hoti hain.

paani ka electrolysis

\begin{aligned} 2 H_{2} O (l) \overset{electricity}{\to} \\ 2 H_{2} (g) + O_{2} (g) \end{aligned}

3/3Hydrogen aur oxygen jama hoti hain, volume mein 2 : 1.

Fig. 1.9Electricity paani ko hydrogen aur oxygen mein tod deti hai.NCERT Fig. 1.6 · p. 9

Lab ka ek apparatus jismein do khadi glass tubes neeche se judi hain, har ek ke base par ek electrode hai, aur yeh battery se juda hai: left electrode negative terminal se aur right wala positive terminal se. Pehle step mein switch khula hai aur dono tubes paani se bhari hain. Doosre step mein switch band hai, dono electrodes se bubbles uthte hain aur upar gas jama hone lagti hai. Teesre step mein left tube mein right wali se do guna gas hai; gases par hydrogen aur oxygen likha hai, do aur ek ke ratio mein.

Activity 1.8NCERT Activity 1.8 · p. 9

Silver chloride par dhoop

Tumhe chahiye

lagbhag 1 g white silver chloride
ek china dish aur ek spatula
ek sikka
tez dhoop

Pehle guess karo

Tum white powder ke ek hisse par sikka rakhte ho aur dish ko dhoop mein chhod dete ho. Sikka uthaane par tumhe kya dikhega?

Saara powder abhi bhi white haiPoori layer grey ho gayi haiSikke ke neeche wala hissa grey hai aur baaki whiteKhula powder grey ho gaya hai; sikke ke neeche wala hissa abhi bhi white hai

Spatula se silver chloride ko dish mein patli layer mein phailao. (Silver salts skin par kaale daag chhodte hain.)
Layer ke beech mein ek sikka halke se dabao.
Dish ko 15–20 minute tak tez dhoop mein chhod do.
Sikka uthao aur layer ke dono hisson ko compare karo.

light mein silver chloride

\begin{aligned} 2 A g C l (s) \overset{sunlight}{\to} \\ 2 A g (s) + C l_{2} (g) \end{aligned}

(1.22)

Silver bromide bhi aisa hi karta hai, aur black-and-white film mein yahi light-sensitive chemical tha:

light mein silver bromide

\begin{aligned} 2 A g B r (s) \overset{sunlight}{\to} \\ 2 A g (s) + B r_{2} (g) \end{aligned}

(1.23)

3/3Khula hissa grey (silver); dhaka hissa abhi bhi white.

Fig. 1.10Light silver chloride ko sirf wahin decompose karti hai jahan woh padti hai.NCERT Fig. 1.7 · p. 9

Silver chloride ki ek dish upar se dikhayi gayi hai. Pehle step mein layer poori white hai. Doosre step mein layer ke beech mein ek sikka rakha hai aur dish par dhoop pad rahi hai. Teesre step mein sikka utha liya gaya hai: khula powder grey hai kyunki silver ban gaya hai, jabki jahan sikke ne light roki thi wahan ek white disc bachi hai.

Pichhli chaar activities ko yaad karo. Burner, battery aur sun, sab kaam kar rahe the, compounds ko todne ke liye energy daal rahe the. Jo reaction is tarah energy sokh leta hai, woh endothermic reaction hai (endo ka matlab hai andar). Kuch reactions apne surroundings se itni heat le lete hain ki flask chhoone mein thanda lagta hai.

Definition

Endothermic reaction

Aisa reaction jo apne surroundings se energy, aam taur par heat ke roop mein, sokhta hai.

ExampleGaram kiln mein limestone ka tootna.

Try karke dekhoNCERT Neeche di gayi Activity karo · p. 10

Ek reaction jo paani ko jama deta hai

Tumhe chahiye

barium hydroxide crystals ka ek spatula
aadha spatula ammonium chloride
ek sookhi test tube aur ek glass rod

Pehle guess karo

Solids milaane ke baad tube ke neeche tumhe kya mehsoos hoga?

Woh bahut thandi ho jaati haiWoh garam ho jaati haiKoi change nahiThodi garam hoti hai, phir phat jaati hai

Teacher dono solids ko sookhi test tube mein glass rod se milaate hain.
Tube ke neeche wale hisse ko apni hatheli se chhuo.
Zyada bada effect dekhne ke liye mixture ko ek chhote flask mein banaya ja sakta hai, jo lakdi ke block par paani ke chhote se puddle mein khada ho. Do minute ruko, phir flask ko uthaane ki koshish karo.

Quick check

4 mein se 1

Har decomposition ko us energy se match karo jo use chalati hai.

Left mein koi item tap karo, phir right mein uska match.

Answer dekho

Answer

Limestone se quicklime : heat
Film mein silver bromide : light
Paani se hydrogen aur oxygen : electricity

Kiln limestone ko garam karta hai, light silver bromide ko kaala karti hai, aur battery paani ko todti hai.

Practice · 2 questions

Ruko aur practice karo 2: answers ke saath

1
Short answerEasyNCERT in-text Questions p. 10, Q1
Ek painter hardware shop se “P” likhe white tukde khareedta hai aur unhe paani ke drum mein daal deta hai. Paani hiss karta hai aur garam ho jaata hai, aur baad mein doodhiya liquid deewaron par brush se lagaya jaata hai.
1. P ka naam aur formula batao.
  Solution dikhao
  AnswerQuicklime, yaani calcium oxide, $C a O$ .
  P quicklime hai, yaani calcium oxide, $C a O$ . Yeh paani ke saath zor se react karta hai, isi se hiss ki awaaz aur heat aati hai.
2. Paani ke saath iske reaction ki equation likho.
  Solution dikhao
  $C a O (s)$ + $H_{2} O (l)$ → $C a (O H)_{2} (a q)$
  Slaked lime, yaani calcium hydroxide, hi whitewash hai; heat nikalti hai.
2
NumericalMediumNCERT in-text Questions p. 10, Q2
Acid mile paani ke electrolysis mein negative terminal se jude electrode ke upar 30 mL gas jama hoti hai.
1. Utne hi samay mein doosre electrode ke upar kitni gas, mL mein, jama hoti hai?
  mL
  Answer dekho
  Answer 15 mL
  Hydrogen negative electrode par aur oxygen positive electrode par jama hoti hai, 2 : 1 ratio mein, isliye $30 \div 2 = 15 m L$ oxygen.
2. Dono gases ke naam batao aur samjhao ki ek ka volume doosre ka do guna kyun hai.
  Solution dikhao
  30 mL hydrogen hai aur 15 mL oxygen. $2 H_{2} O \overset{}{\to} 2 H_{2} + O_{2}$ mein har do water molecules do hydrogen molecules dete hain lekin sirf ek oxygen molecule. Same conditions mein gases ke barabar volumes mein barabar molecules hote hain, isliye hydrogen do guna volume leti hai.

1.2.3 Displacement Reaction

Activity 1.9NCERT Activity 1.9 · p. 10

Neele solution mein iron ki keel

Tumhe chahiye

iron ki do keelein (nails) aur sandpaper
copper sulphate solution (paani mein ghula neela thotha)
do chhote glass bowls
ek chimta (tongs)

Pehle guess karo

Copper sulphate solution mein aadha ghanta rehne ke baad nail kaisi dikhegi?

Bina badle aur greyBlue crystals se dhaki huiPoori tarah ghul gayiBrown si parat se dhaki hui

Dono nails ko chamakne tak ragdo. Compare karne ke liye ek ko sookha rakho.
Dono bowls mein copper sulphate solution barabar gehraai tak daalo.
Doosri nail ko ek bowl mein rakh do. Doosre bowl ko waise hi rehne do.
5 minute baad dekho aur phir aadhe ghante baad. Phir chimte se nail bahar nikaalo aur use sookhi nail se compare karo, aur dono bowls ke colours bhi compare karo.

Table 1.7

Kya compare karna hai	5 min baad	30 min baad
Nail ki surface
Solution ka colour

Tumhari entries apne aap save hoti hain.

iron copper ko displace karta hai

\begin{aligned} F e (s) \\ + C u S O_{4} (a q) \\ \overset{}{\to} F e S O_{4} (a q) \\ + C u (s) \end{aligned}

(1.24)

3/3Close-up: iron solution mein jaata hai, copper bahar aata hai.

Fig. 1.11Iron copper sulphate solution se copper ko displace karta hai.NCERT Fig. 1.8 · p. 10

Copper sulphate solution ke do glass bowls, jin par blue likha hai, saath-saath rakhe hain, aur right bowl mein ek iron nail padi hai. Doosre step mein, aadhe ghante baad, right bowl ke solution par pale green likha hai aur nail par copper likhi brown parat hai, jabki left bowl abhi bhi blue hai. Teesre step mein ek magnified circle nail ki surface dikhata hai: iron atoms iron ions bankar solution mein jaate hain, aur solution ke copper ions copper atoms bankar nail par jam jaate hain.

Is displacement reaction mein ek zyada reactive element kam reactive element ko uske compound se bahar dhakel deta hai. Iron copper se zyada reactive hai, isliye woh sulphate le leta hai aur copper ko metal ki tarah chhod deta hai. Zinc bhi yahi karta hai, aur blue solution colourless ho jaata hai kyunki zinc sulphate ka koi colour nahi hota:

zinc copper ko displace karta hai

\begin{aligned} Z n (s) \\ + C u S O_{4} (a q) \\ \overset{}{\to} Z n S O_{4} (a q) \\ + C u (s) \end{aligned}

(1.25)

Roles badal do to kuch nahi hota. Iron sulphate solution mein chhodi gayi copper wire chamakdaar hi rehti hai, kyunki copper iron se kam reactive hai aur use bahar nahi dhakel sakta. Chapter 3 mein tum metals ko ek reactivity series mein rank karoge.

Definition

Displacement reaction

Aisa reaction jismein ek zyada reactive element kisi kam reactive element ki jagah uske compound mein le leta hai.

ExampleCopper sulphate solution se iron ka copper ko displace karna.

1.2.4 Double Displacement Reaction

Activity 1.10NCERT Activity 1.10 · p. 11

Saaf plus saaf se bana white

Tumhe chahiye

sodium sulphate ka solution
barium chloride ka solution
do test tubes
ek measuring cylinder ya dropper

Pehle guess karo

Do saaf solutions milaane par tumhe kya dikhega?

Ek white solid jo liquid ko dhundhla kar deta haiEk blue solutionGas ke bubblesBilkul kuch nahi

Ek test tube mein 2 mL barium chloride solution lo aur use kisi dark background ke saamne pakdo.
Sodium sulphate solution kuch-kuch boondein karke daalo, har baar daalne ke baad halke se hilao.
Jab aur dhundhlapan na bane tab ruk jaao, phir tube ko paanch minute khada rehne do.

ek white precipitate

\begin{aligned} N a_{2} S O_{4} (a q) \\ + B a C l_{2} (a q) \\ \overset{}{\to} B a S O_{4} (s) \\ + 2 N a C l (a q) \end{aligned}

(1.27)

3/3Barium sulphate precipitate ki tarah neeche baithta hai.

Fig. 1.12Double displacement mein do compounds apne partners badal lete hain.NCERT Fig. 1.9 · p. 11

Ions ko label wali shapes ki tarah dikhaya gaya hai: sodium aur barium circles hain, sulphate aur chloride gol kinaron wale squares. Pehle step mein sodium sulphate ke saath aur barium chloride ke saath jode mein hai, jaise shuru ke do solutions mein. Doosre step mein cross karte arrows partners ki adla-badli dikhate hain. Teesre step mein barium sulphate beaker ke neeche white solid ki tarah baitha hai, jis par precipitate likha hai, jabki sodium aur chloride upar ke liquid mein ghule rehte hain.

Har ghule hue compound ko dance partners ke jodon ki tarah socho: ek beaker mein sodium ions sulphate ions ke saath, doosre mein barium ions chloride ions ke saath. Dono beakers ko milao aur partners badal jaate hain. Ab barium sulphate se milta hai, aur yeh jodi ghuli nahi reh sakti, isliye solid bankar bahar aa jaati hai. Sodium aur chloride ions paani mein aazaad tairte rehte hain:

jo ions react karte hain

\begin{aligned} B a^{2 +} (a q) \\ + S O_{4}^{2 -} (a q) \\ \overset{}{\to} B a S O_{4} (s) \end{aligned}

Kyunki dono compounds ne partners badle hain, yeh ek double displacement reaction hai. Aise reactions, jinmein ek insoluble solid banta hai, precipitation reactions bhi kehlaate hain, aur kai double displacements isi tarah ke hote hain. Jaise, neele copper sulphate solution mein sodium hydroxide solution daalo, to copper hydroxide ka halka blue, jelly jaisa precipitate dikhta hai:

ek blue precipitate

\begin{aligned} C u S O_{4} (a q) \\ + 2 N a O H (a q) \\ \overset{}{\to} C u (O H)_{2} (s) \\ + N a_{2} S O_{4} (a q) \end{aligned}

Definition

Double displacement reaction

Aisa reaction jismein do compounds apne ions badalkar do naye compounds banate hain.

ExampleSodium sulphate aur barium chloride se barium sulphate aur sodium chloride banna.

Definition

Precipitate

Solutions ke react karne par banne wala insoluble solid; yeh liquid ko dhundhla karta hai aur phir neeche baith jaata hai.

ExampleJaise white barium sulphate; yellow lead iodide.

Quick check

3 mein se 1

Jab sodium sulphate aur barium chloride solutions milaaye jaate hain, to kaunsa substance precipitate hai?

Sodium chlorideBarium chlorideSodium sulphateBarium sulphate

Answer dekho

Answer (D) Barium sulphate

Barium sulphate insoluble hai aur white solid ki tarah bahar aata hai. Sodium chloride bhi product hai, lekin woh ghula hua rehta hai.

1.2.5 Oxidation aur Reduction

Activity 1.11NCERT Activity 1.11 · p. 12

Ek copper wire jo kaali pad jaati hai

Tumhe chahiye

nangi copper wire ka 10 cm ka tukda (kisi purani cable se nikala hua)
sandpaper
chimta (tongs)
ek burner
ek tile

Pehle guess karo

Jahan flame chhooti hai, wahan copper ka colour kya ho jaayega?

HaraKaalaChaandi jaisaWoh reddish brown hi rehta hai

Wire ko tab tak ragdo jab tak woh chamakdaar reddish brown na ho jaaye.
Ek end ko chimte se pakdo aur beech ke hisse ko ek minute tak flame mein garam karo.
Use tile par thanda hone do, aur garam kiye hisse ko bina garam kiye end se compare karo.

copper oxygen leta hai

\begin{aligned} 2 C u + O_{2} \\ \overset{heat}{\to} 2 C u O \end{aligned}

(1.28)

copper oxide oxygen khota hai

\begin{aligned} C u O + H_{2} \\ \overset{heat}{\to} C u + H_{2} O \end{aligned}

(1.29)

(1.29) mein oxygen atom ko follow karo. Woh shuru mein copper se juda hai aur aakhir mein hydrogen se jud jaata hai. Chemists ke paas is safar ke dono siron ke liye ek-ek shabd hai. Jo bhi oxygen leta hai, woh oxidised hua hai (oxidation); jo bhi oxygen khota hai, woh reduced hua hai (reduction). To hydrogen oxidise hokar paani banti hai, aur copper oxide reduce hokar copper banta hai.

Oxygen atom ek substance ko chhod kar kisi doosre par pahunche bina nahi ja sakta, isliye yeh dono processes hamesha jodi mein aate hain. Jis reaction mein dono hon, woh redox reaction hai, jo reduction–oxidation ka chhota roop hai.

Definition

Oxidation

Reaction mein kisi substance ka oxygen lena, ya hydrogen khona.

ExampleHawa mein garam karne par copper ka copper oxide ban jaana.

Definition

Reduction

Reaction mein kisi substance ka oxygen khona, ya hydrogen lena. Yeh hamesha oxidation ke saath hi hota hai.

ExampleHydrogen mein copper oxide ka wapas copper ban jaana.

Iron bahut bade paimaane par ek redox reaction se banta hai. Bhilai aur Jamshedpur jaise steel plants ki blast furnaces mein carbon monoxide iron ore se oxygen kheench leti hai. Fig. 1.13 dikhata hai ki oxygen kahan jaati hai.

3/3 $C O$ oxygen leta hai: oxidised.

Fig. 1.13Blast furnace mein iron ore reduce hota hai jabki carbon monoxide oxidise hoti hai.

Beech mein woh equation likhi hai jismein Fe2O3 plus 3CO milkar 2Fe plus 3CO2 dete hain. Pehle step mein woh akeli hai. Doosre step mein equation ke neeche ek arrow Fe2O3 se 2Fe tak jaata hai, jis par loses oxygen aur reduced likha hai. Teesre step mein equation ke upar ek arrow 3CO se 3CO2 tak jaata hai, jis par gains oxygen aur oxidised likha hai, to redox reaction ke dono hisse mark ho jaate hain.

Hydrogen bhi marker ka kaam karti hai, lekin ulte sense mein: hydrogen khona oxidation hai aur hydrogen lena reduction hai. Jab hydrogen sulphide chlorine se milti hai, to hydrogen sulphide apni hydrogen kho kar sulphur ban jaati hai, isliye woh oxidise hoti hai. Chlorine woh hydrogen le kar hydrogen chloride ban jaati hai, isliye woh reduce hoti hai:

bina oxygen ke redox

\begin{aligned} H_{2} S + C l_{2} \\ \overset{}{\to} 2 H C l + S \end{aligned}

Practice · 3 questions

Ruko aur practice karo 3: answers ke saath

Short answerEasyNCERT in-text Questions p. 13, Q1
Ek student neele copper sulphate solution ko kuch minute tak zinc ke spatula se chalata hai. Blue colour dheere-dheere fika pad jaata hai. Equation ke saath samjhao kyun.
Solution dikhao
Zinc copper se zyada reactive hai, isliye woh copper sulphate se copper ko displace karta hai. Copper spatula par brown layer ki tarah jam jaata hai, aur neele copper sulphate ki jagah colourless zinc sulphate aa jaata hai, isliye colour fika pad jaata hai.
$Z n (s)$ + $C u S O_{4} (a q)$ → $Z n S O_{4} (a q)$ + $C u (s)$
Short answerMediumNCERT in-text Questions p. 13, Q2
Aise do solutions ke naam batao jo milaane par double displacement se coloured precipitate dete hain. Equation likho, aur precipitate aur uska colour batao.
Solution dikhao
Copper sulphate sodium hydroxide ke saath copper hydroxide ka halka blue precipitate deta hai:
$C u S O_{4} (a q)$ + $2 N a O H (a q)$ → $C u (O H)_{2} (s)$ + $N a_{2} S O_{4} (a q)$
Ek aur answer: lead nitrate potassium iodide ke saath lead iodide ka yellow precipitate deta hai.
3
Short answerMediumNCERT in-text Questions p. 13, Q3
Har reaction mein oxidise hone wala aur reduce hone wala substance batao.
1. Ore se tin: $S n O_{2} + 2 C \overset{}{\to} S n + 2 C O$
  Solution dikhao
  $S n O_{2}$ oxygen khota hai, isliye woh reduce hota hai. Carbon oxygen lekar CO banta hai, isliye woh oxidise hota hai.
2. Oxide se lead: $P b O + C O \overset{}{\to} P b + C O_{2}$
  Solution dikhao
  $P b O$ oxygen khota hai aur reduce hota hai. Carbon monoxide oxygen lekar $C O_{2}$ banti hai aur oxidise hoti hai.

1.3 Kya Tumne Roz ki Zindagi mein Oxidation Reactions ke Effects Dekhe Hain?

Oxidation sirf laboratory ka idea nahi hai. Hawa ka lagbhag paanchwa hissa oxygen hai, aur yeh hamare aas-paas ki cheezon ko dheere-dheere oxidise karti hai. Iske do roz ke results hain corrosion aur rancidity.

1.3.1 Corrosion

Pichhli Diwali par paint kiya gaya iron ka gate monsoon khatam hote-hote orange-brown papdiyan dikha sakta hai. Woh papdi wali layer rust (jung) hai, jo iron ke oxygen aur paani se react karne par banti hai. Doosre metals bhi isse bache nahi: chaandi ki payal dheere-dheere kaali pad jaati hai, aur copper ya brass ke lote par ek dhundhli hari parat chadh jaati hai. Aas-paas ki hawa, paani, acids ya doosre chemicals se metal ka is tarah dheere-dheere khaaya jaana corrosion kehlaata hai.

3/3Mahinon baad: rust, kaala tarnish aur hari parat.

Fig. 1.14Teen metals, teen tarah ka corrosion.

Teen cheezein saath-saath khadi hain: iron gate ka ek hissa, chaandi ki payal aur copper ka lota. Pehle step mein teeno nayi aur chamakdaar hain. Doosre step mein air aur moisture likhe arrows teeno tak pahunchte hain. Teesre step mein gate par reddish-brown rust ke dhabbe hain, payal kaali pad gayi hai aur lote par hare dhabbe hain, aur har ek par uski parat ka naam likha hai.

Sahi kahein to chaandi par kaali layer silver sulphide hai, jo hawa mein maujood sulphur compounds ke ansh se banti hai, aur copper par hari parat basic copper carbonate hai jo hawa, paani aur carbon dioxide se banti hai. Har ek metal aur uske surroundings ke beech ek slow reaction hai.

Rust mehnga padta hai. Jung laga bolt signboard gira sakta hai, corrode hua water pipe leak karta hai, aur railway lines aur samundar kinare ke structures ko lagataar check aur repaint karna padta hai. Isliye hum iron aur hawa ke beech ek barrier lagate hain: railings ko paint karte hain, cycle ki chain mein oil daalte hain aur kai baaltiyon par zinc ki coating hoti hai. Chapter 3 rusting aur use rokne ke tareekon ko aur detail mein samjhata hai.

Definition

Corrosion

Aas-paas ki hawa, nami, acids ya doosre substances se metal ka dheere-dheere kharaab hona.

ExampleIron par rust lagna; chaandi par kaala tarnish; copper par hari parat.

1.3.2 Rancidity

Bhooli hui namkeen ka packet kholo, ya baar-baar talne mein use hue oil ko sungho. Baasi, buri smell aur kadwa taste rancidity ke nishaan hain: hawa ne khane ke fats aur oils ko oxidise kar diya hai. Light aur garmi ise aur tez kar dete hain.

2/2Andar nitrogen: chips fresh rehte hain.

Fig. 1.15Nitrogen chips ke oil se oxygen ko door rakhti hai.

Chips ke do sealed packets saath-saath bane hain. Pehle step mein sirf left packet dikhta hai: usmein hawa hai, chips ke beech oxygen molecules O circles ke jodon ki tarah bane hain, aur baasi smell ke liye lehardaar lines upar uthti hain. Doosre step mein right packet dikhta hai, jo nitrogen molecules se bhara hai, jo N circles ke jodon ki tarah bane hain; uske chips par smell ki lines nahi hain aur un par fresh likha hai.

Hum oxygen ko door rakh kar, ya oxidation ko dheema karke, rancidity ko dheema karte hain:

Khana airtight containers mein, thandi aur andheri jagah par ya fridge mein rakho.
Antioxidants daalo, yaani aise substances jo fat se pehle aur aasani se oxygen se react karte hain aur is tarah fat ko bachaate hain. Kai oils mein Vitamin E yeh kaam naturally karta hai; packet ke labels par BHA ya BHT jaise doosre antioxidants likhe hote hain.
Packets mein nitrogen bharo. Chips banane wale bags ko seal karne se pehle unmein nitrogen bhar dete hain, isiliye packet phoola hua lagta hai. Nitrogen oil se react nahi karti, isliye chips kaafi lambe samay tak crisp aur fresh rehte hain.

Definition

Rancidity

Hawa se khane ke fats aur oils ka oxidation, jisse unki smell aur taste kharaab ho jaate hain.

ExamplePurani namkeen jisse baasi smell aati hai.

Recap

Summary aur key points

Reaction kuch naya banata hai. Naye colour, gas, temperature ke change ya solid ke dikhne par dhyaan do (Reaction pehchaanna).
Word equation reactants aur products ke naam batata hai; chemical equation formulae use karti hai, jismein reactants arrow ke left mein aur products right mein hote hain (Section 1.1).
Reaction sirf atoms ko rearrange karta hai, isliye arrow ki dono sides par har element ki ginti barabar honi chahiye: equation balance honi chahiye (Section 1.1.2).
Sirf coefficients badalkar balance karo, subscripts kabhi nahi, aur aakhir mein sabse chhote whole numbers par pahuncho (hit-and-trial).
State symbols (s), (l), (g) aur (aq), aur arrow par likhi conditions, equation ko zyada jaankaari wala banate hain (state symbols).
Combination: kai reactants, ek product, jaise jab quicklime paani se milta hai (Section 1.2.1).
Decomposition: ek compound tootkar simple substances ban jaata hai, jise heat, light ya electricity chalati hai (Section 1.2.2).
Heat bahar (exothermic): jalna, respiration, quicklime aur paani. Energy andar (endothermic): zyadatar decompositions.
Displacement: zyada reactive metal kam reactive metal ko uske compound se bahar dhakel deta hai, jaise iron copper ke saath karta hai (Section 1.2.3).
Double displacement: do compounds apne partner ions badal lete hain; jab is adla-badli se insoluble solid banta hai, to yeh precipitation reaction bhi hai (Section 1.2.4).
Jo substance oxygen leta hai ya hydrogen deta hai, woh oxidise hota hai; jo oxygen deta hai ya hydrogen leta hai, woh reduce hota hai. Yeh dono changes hamesha jodi mein, redox reactions mein, aate hain (Section 1.2.5).
Metals ka corrosion aur fats aur oils ki rancidity oxidation ke roz ke effects hain (Section 1.3).

Group mein activityNCERT Group Activity · p. 16

Garam ya thanda? Chaar reactions, ek thermometer

Tumhe chahiye

A, B, C aur D likhe chaar glass
ek thermometer
fruit salt (jaise ENO) aur paani
baking soda aur sirka (vinegar)
steel wool ka ek pad aur vinegar
dilute hydrochloric acid aur dilute sodium hydroxide solution (school lab)

Pehle guess karo

Tumhe kya lagta hai, kaunse mixtures garam honge?

A: paani mein fruit saltB: vinegar mein baking sodaC: vinegar mein bheega steel woolD: alkali ke saath mila acid

Saare sahi options chuno

A mein 50 mL paani aur B mein 50 mL vinegar daalo. Har ek ka temperature naapo aur likho.
A mein ek chammach fruit salt aur B mein ek chammach baking soda daalo. Chalao, ek minute ruko aur phir se temperatures likho.
Steel wool ko ek minute vinegar mein bhigo kar nichod lo. Use glass C ke andar thermometer ke bulb ke chaaron taraf lapeto aur glass ko paper se dhak do. Abhi ka aur paanch minute baad ka temperature likho.
D mein teacher 20 mL dilute hydrochloric acid ko 20 mL dilute sodium hydroxide solution ke saath milaate hain. Milaane se pehle aur baad ka temperature likho.

Table 1.8

Glass	Shuru (°C)	Aakhir (°C)	Exo ya endo?
A
B
C
D

Tumhari entries apne aap save hoti hain.

A aur B kuch degree thande ho jaate hain, isliye yeh reactions endothermic hain; fizz reaction se bani carbon dioxide hai. C dheere-dheere garam hota hai: vinegar steel wool ki bachaav wali film hata deta hai aur iron mein rust lagne lagta hai, jo ek exothermic oxidation hai. D jaldi garam hota hai, kyunki acid ka alkali ke saath reaction heat chhodta hai. Shuru aur aakhir ke temperatures compare karna exothermic aur endothermic reactions ko alag karne ka sabse simple tareeka hai.

Apna NCERT exercise question dhoondo

Hamare practice questions ncert.ai ke liye likhe gaye hain aur NCERT exercises ko follow karte hain. Apni textbook ke question se match karne wala question dhoondo; uska answer uske saath hai.

Tumhari NCERT textbook mein	Yahan practice question
NCERT in-text Questions p. 6, Q1	Ruko aur practice karo 1 · Q1
NCERT in-text Questions p. 6, Q2	Ruko aur practice karo 1 · Q2
NCERT in-text Questions p. 6, Q3	Ruko aur practice karo 1 · Q3
NCERT in-text Questions p. 10, Q1	Ruko aur practice karo 2 · Q1
NCERT in-text Questions p. 10, Q2	Ruko aur practice karo 2 · Q2
NCERT in-text Questions p. 13, Q1	Ruko aur practice karo 3 · Q1
NCERT in-text Questions p. 13, Q2	Ruko aur practice karo 3 · Q2
NCERT in-text Questions p. 13, Q3	Ruko aur practice karo 3 · Q3
NCERT Exercises Q1	Exercises · Q1
NCERT Exercises Q2	Exercises · Q2
NCERT Exercises Q3	Exercises · Q3
NCERT Exercises Q4	Exercises · Q4
NCERT Exercises Q5	Exercises · Q5
NCERT Exercises Q6	Exercises · Q6
NCERT Exercises Q7	Exercises · Q7
NCERT Exercises Q8	Exercises · Q8
NCERT Exercises Q9	Exercises · Q9
NCERT Exercises Q10	Exercises · Q10
NCERT Exercises Q11	Exercises · Q11
NCERT Exercises Q12	Exercises · Q12
NCERT Exercises Q13	Exercises · Q13
NCERT Exercises Q14	Exercises · Q14
NCERT Exercises Q15	Exercises · Q15
NCERT Exercises Q16	Exercises · Q16
NCERT Exercises Q17	Exercises · Q17
NCERT Exercises Q18	Exercises · Q18
NCERT Exercises Q19	Exercises · Q19
NCERT Exercises Q20	Exercises · Q20

Quick check: MCQs

Chemical reaction pehchaanna3 questions
Physical states likhna4 questions
1.2.1 Combination Reaction3 questions
1.2.2 Decomposition Reaction4 questions
1.2.3 Displacement Reaction3 questions
1.2.4 Double Displacement Reaction3 questions
1.2.5 Oxidation aur Reduction3 questions
1.3.2 Rancidity3 questions

Glossary · 15

Key terms (English + Hindi)

balanced equationसंतुलित समीकरणsantulit samikaran: Aisi equation jismein har element ke atoms dono sides par barabar hon. Bina balance ka draft skeletal equation hai.Chapter mein pehli baar yahan aaya →

chemical equationरासायनिक समीकरणrasayanik samikaran: Chemical formulae se likha gaya reaction: left mein reactants, phir arrow, aur right mein products.Chapter mein pehli baar yahan aaya →
combination reactionसंयोजन अभिक्रियाsanyojan abhikriya: Do ya zyada reactants judkar ek hi product banate hain.Chapter mein pehli baar yahan aaya →
corrosionसंक्षारणsankshaaran: Aas-paas ki hawa, nami, acids ya doosre substances se metal ka dheere-dheere khaaya jaana.Chapter mein pehli baar yahan aaya →

decomposition reactionवियोजन अभिक्रियाviyojan abhikriya: Ek reactant tootkar do ya zyada simple products ban jaata hai.Chapter mein pehli baar yahan aaya →
displacement reactionविस्थापन अभिक्रियाvisthapan abhikriya: Zyada reactive element kam reactive element ki jagah uske compound mein le leta hai.Chapter mein pehli baar yahan aaya →
double displacement reactionद्विविस्थापन अभिक्रियाdvivisthapan abhikriya: Do compounds ions badalkar do naye compounds banate hain.Chapter mein pehli baar yahan aaya →

endothermic reactionऊष्माशोषी अभिक्रियाushmashoshi abhikriya: Aisa reaction jo energy leta hai, aam taur par heat ke roop mein.Chapter mein pehli baar yahan aaya →
exothermic reactionऊष्माक्षेपी अभिक्रियाushmakshepi abhikriya: Aisa reaction jo heat chhodta hai.Chapter mein pehli baar yahan aaya →

oxidationउपचयनupachayan: Kisi substance ka oxygen lena ya hydrogen khona.Chapter mein pehli baar yahan aaya →

precipitateअवक्षेपavakshep: Reaction ke dauraan solution mein banne wala insoluble solid.Chapter mein pehli baar yahan aaya →
productउत्पादutpad: Reaction mein bana naya substance.Chapter mein pehli baar yahan aaya →

rancidityविकृतगंधिताvikritgandhita: Oxidation se khane ke fats aur oils ka kharaab hona, jisse unki smell aur taste badal jaate hain.Chapter mein pehli baar yahan aaya →
reactantअभिकारकabhikarak: Aisa substance jo reaction mein use hota hai aur badal jaata hai.Chapter mein pehli baar yahan aaya →
reductionअपचयनapachayan: Kisi substance ka oxygen khona ya hydrogen lena. Yeh hamesha oxidation ke saath jodi mein hota hai (redox reaction).Chapter mein pehli baar yahan aaya →

Chemical Reactions and Equations: Class 10 Science Chapter 1 Hinglish mein

Is chapter mein aap kya seekhenge

Chemical reaction pehchaanna

1.1 Chemical Equations

1.1.1 Chemical Equation Likhna

1.1.2 Balanced Chemical Equations

Hit-and-trial se balance karna

Physical states likhna

Ruko aur practice karo 1: answers ke saath

1.2 Chemical Reactions ke Types

1.2.1 Combination Reaction

1.2.2 Decomposition Reaction

Ruko aur practice karo 2: answers ke saath

1.2.3 Displacement Reaction

1.2.4 Double Displacement Reaction

1.2.5 Oxidation aur Reduction

Ruko aur practice karo 3: answers ke saath

1.3 Kya Tumne Roz ki Zindagi mein Oxidation Reactions ke Effects Dekhe Hain?

1.3.1 Corrosion

1.3.2 Rancidity

Summary aur key points

Practice questions answers ke saath (NCERT “Exercises”)

Apna NCERT exercise question dhoondo

Quick check: MCQs

Key terms (English + Hindi)

Tum chapter ke end tak pahunch gaye