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@@ -1004,8 +1004,8 @@ Lead-free solder & Sn, Cu, Ag & Low melting, no lead toxicity & Electronics \\
 Pewter & Sn (85-99\%), Sb, Cu & Soft, silvery, malleable & Decorative items \\
 Babbitt metal & Sn, Sb, Cu & Low friction, soft & Bearing surfaces \\
 Type metal & Pb, Sn, Sb & Expands on cooling & Printing type \\
-Wood's metal & Bi, Pb, Sn, Cd & Very low melting (70°C) & Fire sprinklers, fuses \\
-Rose's metal & Bi, Pb, Sn & Low melting (98°C) & Fusible alloys \\
+Wood's metal & Bi, Pb, Sn, Cd & Very low melting (70$^\circ$C) & Fire sprinklers, fuses \\
+Rose's metal & Bi, Pb, Sn & Low melting (98$^\circ$C) & Fusible alloys \\
 Nichrome & Ni (80\%), Cr (20\%) & High electrical resistance, heat-resistant & Heating elements \\
 Monel metal & Ni (67\%), Cu (30\%) & Corrosion-resistant, strong & Marine, chemical \\
 Invar & Fe (64\%), Ni (36\%) & Very low thermal expansion & Precision instruments \\
@@ -1031,6 +1031,487 @@ Bell metal & Cu (78\%), Sn (22\%) & Resonant, hard & Bells, cymbals \\
 
 \section{Reactions}
 
+\subsection{Types of reactions}
+
+\subsubsection{Combination reaction (Synthesis reaction)}
+
+\textbf{Definition:} Two or more substances combine to form a single product.
+
+\textbf{General form:} \ce{A + B -> AB}
+
+\textbf{Examples:}
+\begin{itemize}
+\item Formation of water: \ce{2H2 + O2 -> 2H2O}
+\item Formation of ammonia: \ce{N2 + 3H2 -> 2NH3}
+\item Metal oxide formation: \ce{2Mg + O2 -> 2MgO}
+\item Salt formation: \ce{2Na + Cl2 -> 2NaCl}
+\end{itemize}
+
+\subsubsection{Decomposition reaction}
+
+\textbf{Definition:} A single compound breaks down into two or more simpler substances.
+
+\textbf{General form:} \ce{AB -> A + B}
+
+\textbf{Examples:}
+\begin{itemize}
+\item Thermal decomposition of calcium carbonate: \ce{CaCO3 ->[heat] CaO + CO2 ^}
+\item Electrolysis of water: \ce{2H2O ->[electrolysis] 2H2 ^ + O2 ^}
+\item Decomposition of hydrogen peroxide: \ce{2H2O2 ->[MnO2] 2H2O + O2 ^}
+\item Decomposition of potassium chlorate: \ce{2KClO3 ->[heat] 2KCl + 3O2 ^}
+\end{itemize}
+
+\subsubsection{Displacement reaction (Substitution reaction)}
+
+\textbf{Definition:} One element replaces another element in a compound.
+
+\textbf{General form:} \ce{A + BC -> AC + B}
+
+\textbf{Examples:}
+\begin{itemize}
+\item Zinc displacing hydrogen: \ce{Zn + 2HCl -> ZnCl2 + H2 ^}
+\item Chlorine displacing bromine: \ce{Cl2 + 2NaBr -> 2NaCl + Br2}
+\item Magnesium displacing copper: \ce{Mg + CuSO4 -> MgSO4 + Cu}
+\item Iron displacing copper: \ce{Fe + CuSO4 -> FeSO4 + Cu}
+\end{itemize}
+
+\subsubsection{Double displacement reaction (Metathesis reaction)}
+
+\textbf{Definition:} Exchange of ions between two compounds.
+
+\textbf{General form:} \ce{AB + CD -> AD + CB}
+
+\textbf{Examples:}
+\begin{itemize}
+\item Precipitation: \ce{AgNO3 + NaCl -> AgCl v + NaNO3}
+\item Neutralization: \ce{HCl + NaOH -> NaCl + H2O}
+\item Formation of barium sulfate: \ce{BaCl2 + H2SO4 -> BaSO4 v + 2HCl}
+\end{itemize}
+
+\subsubsection{Redox reaction (Oxidation-reduction reaction)}
+
+\textbf{Definition:} Transfer of electrons between species, involving change in oxidation states.
+
+\textbf{Oxidation:} Loss of electrons, increase in oxidation number.
+
+\textbf{Reduction:} Gain of electrons, decrease in oxidation number.
+
+\textbf{Examples:}
+\begin{itemize}
+\item Combustion: \ce{C + O2 -> CO2}
+\item Permanganate oxidation: \ce{2KMnO4 + 5H2C2O4 + 3H2SO4 -> K2SO4 + 2MnSO4 + 10CO2 ^ + 8H2O}
+\item Dichromate oxidation: \ce{K2Cr2O7 + 14HCl -> 2KCl + 2CrCl3 + 3Cl2 ^ + 7H2O}
+\item Zinc-copper cell: \ce{Zn + Cu^2+ -> Zn^2+ + Cu}
+\end{itemize}
+
+\subsubsection{Acid-base reaction (Neutralization)}
+
+\textbf{Definition:} Reaction between an acid and a base to produce salt and water.
+
+\textbf{General form:} \ce{Acid + Base -> Salt + Water}
+
+\textbf{Examples:}
+\begin{itemize}
+\item Strong acid-strong base: \ce{HCl + NaOH -> NaCl + H2O}
+\item Weak acid-strong base: \ce{CH3COOH + NaOH -> CH3COONa + H2O}
+\item Dibasic acid: \ce{H2SO4 + 2KOH -> K2SO4 + 2H2O}
+\item Carbonate with acid: \ce{Na2CO3 + 2HCl -> 2NaCl + H2O + CO2 ^}
+\end{itemize}
+
+\subsubsection{Precipitation reaction}
+
+\textbf{Definition:} Formation of an insoluble solid (precipitate) from aqueous solutions.
+
+\textbf{Examples:}
+\begin{itemize}
+\item Silver chloride: \ce{Ag+ + Cl- -> AgCl v} (white precipitate)
+\item Lead iodide: \ce{Pb^2+ + 2I- -> PbI2 v} (yellow precipitate)
+\item Iron(III) hydroxide: \ce{Fe^3+ + 3OH- -> Fe(OH)3 v} (brown precipitate)
+\item Copper(II) hydroxide: \ce{Cu^2+ + 2OH- -> Cu(OH)2 v} (blue precipitate)
+\end{itemize}
+
+\subsection{Organic reactions}
+
+\subsubsection{Halogenation reaction}
+
+\textbf{Definition:} Introduction of halogen atoms (F, Cl, Br, I) into organic molecules.
+
+\textbf{Free radical halogenation (alkanes):}
+\begin{itemize}
+\item Chlorination of methane: \ce{CH4 + Cl2 ->[UV light] CH3Cl + HCl}
+\item Further substitution: \ce{CH3Cl + Cl2 -> CH2Cl2 + HCl}
+\item Bromination of ethane: \ce{C2H6 + Br2 ->[UV light] C2H5Br + HBr}
+\end{itemize}
+
+\textbf{Electrophilic halogenation (aromatic):}
+\begin{itemize}
+\item Bromination of benzene: \ce{C6H6 + Br2 ->[FeBr3] C6H5Br + HBr}
+\item Chlorination of benzene: \ce{C6H6 + Cl2 ->[AlCl3] C6H5Cl + HCl}
+\item Iodination of benzene: \ce{C6H6 + I2 ->[HNO3] C6H5I + HI}
+\end{itemize}
+
+\textbf{Addition halogenation (alkenes):}
+\begin{itemize}
+\item Bromination of ethene: \ce{C2H4 + Br2 -> C2H4Br2}
+\item Test for unsaturation: Decolorization of bromine water
+\item Chlorination of propene: \ce{C3H6 + Cl2 -> C3H6Cl2}
+\end{itemize}
+
+\subsubsection{Nucleophilic substitution}
+
+\textbf{Definition:} Replacement of a leaving group by a nucleophile.
+
+\textbf{S$_{\mathbf{N}}$1 mechanism (unimolecular):}
+\begin{itemize}
+\item Two-step process via carbocation intermediate
+\item Rate depends only on substrate concentration
+\item Favored by tertiary halides and polar solvents
+\item Example: \ce{(CH3)3CBr + H2O -> (CH3)3COH + HBr}
+\end{itemize}
+
+\textbf{S$_{\mathbf{N}}$2 mechanism (bimolecular):}
+\begin{itemize}
+\item One-step process with backside attack
+\item Rate depends on both substrate and nucleophile concentration
+\item Favored by primary halides and aprotic solvents
+\item Inversion of configuration (Walden inversion)
+\item Example: \ce{CH3Br + OH- -> CH3OH + Br-}
+\end{itemize}
+
+\textbf{Common nucleophiles:}
+\begin{itemize}
+\item Hydroxide (OH$^-$): Forms alcohols
+\item Alkoxide (RO$^-$): Forms ethers
+\item Cyanide (CN$^-$): Forms nitriles
+\item Ammonia (NH$_3$): Forms amines
+\item Water (H$_2$O): Forms alcohols (weak nucleophile)
+\end{itemize}
+
+\subsubsection{Nucleophilic addition}
+
+\textbf{Definition:} Addition of a nucleophile to a carbonyl group.
+
+\textbf{Examples:}
+\begin{itemize}
+\item Cyanohydrin formation: \ce{CH3CHO + HCN -> CH3CH(OH)CN}
+\item Grignard addition: \ce{CH3MgBr + CH2O -> CH3CH2OH} (after hydrolysis)
+\item Bisulfite addition: \ce{RCHO + NaHSO3 -> RCH(OH)SO3Na}
+\end{itemize}
+
+\subsubsection{Electrophilic addition}
+
+\textbf{Definition:} Addition of an electrophile to a multiple bond.
+
+\textbf{Examples:}
+\begin{itemize}
+\item Hydrohalogenation: \ce{C2H4 + HBr -> C2H5Br}
+\item Markovnikov's rule: H adds to carbon with more H atoms
+\item Hydration: \ce{C2H4 + H2O ->[H+] C2H5OH}
+\item Addition of sulfuric acid: \ce{C2H4 + H2SO4 -> C2H5OSO3H}
+\end{itemize}
+
+\subsubsection{Elimination reaction}
+
+\textbf{Definition:} Removal of atoms or groups to form multiple bonds.
+
+\textbf{Dehydrohalogenation (E1 and E2):}
+\begin{itemize}
+\item E2 mechanism: \ce{C2H5Br + KOH ->[alcohol, heat] C2H4 ^ + KBr + H2O}
+\item Zaitsev's rule: Major product is more substituted alkene
+\item E1 mechanism: Two-step via carbocation
+\end{itemize}
+
+\textbf{Dehydration of alcohols:}
+\begin{itemize}
+\item Ethanol dehydration: \ce{C2H5OH ->[H2SO4, heat] C2H4 ^ + H2O}
+\item Intramolecular (forms alkene) vs intermolecular (forms ether)
+\end{itemize}
+
+\subsubsection{Oxidation reactions}
+
+\textbf{Oxidation of alcohols:}
+\begin{itemize}
+\item Primary to aldehyde: \ce{RCH2OH ->[oxidation] RCHO ->[oxidation] RCOOH}
+\item Secondary to ketone: \ce{R2CHOH ->[oxidation] R2CO}
+\item Tertiary alcohols: Resistant to oxidation
+\item Oxidizing agents: \ce{K2Cr2O7/H2SO4}, \ce{KMnO4}, \ce{CrO3}
+\end{itemize}
+
+\textbf{Oxidation of aldehydes:}
+\begin{itemize}
+\item To carboxylic acid: \ce{RCHO ->[oxidation] RCOOH}
+\item Mild oxidizing agents work (e.g., Tollens' reagent, Fehling's reagent)
+\end{itemize}
+
+\subsubsection{Reduction reactions}
+
+\textbf{Reduction of carbonyl compounds:}
+\begin{itemize}
+\item Aldehyde to primary alcohol: \ce{RCHO ->[reduction] RCH2OH}
+\item Ketone to secondary alcohol: \ce{R2CO ->[reduction] R2CHOH}
+\item Reducing agents: \ce{LiAlH4}, \ce{NaBH4}, \ce{H2/Pt}
+\end{itemize}
+
+\textbf{Reduction of carboxylic acids:}
+\begin{itemize}
+\item To primary alcohol: \ce{RCOOH ->[LiAlH4] RCH2OH}
+\item Requires strong reducing agent
+\end{itemize}
+
+\subsubsection{Condensation reactions}
+
+\textbf{Definition:} Combination of molecules with elimination of small molecule (usually water).
+
+\textbf{Esterification:}
+\begin{itemize}
+\item Fischer esterification: \ce{RCOOH + R-OH <=>[H+] RCOOR + H2O}
+\item Reversible reaction, equilibrium can be shifted
+\end{itemize}
+
+\textbf{Aldol condensation:}
+\begin{itemize}
+\item Self-condensation of aldehydes: \ce{2CH3CHO ->[OH-] CH3CH(OH)CH2CHO}
+\item Followed by dehydration: \ce{CH3CH(OH)CH2CHO -> CH3CH=CHCHO + H2O}
+\end{itemize}
+
+\subsubsection{Hydrolysis reactions}
+
+\textbf{Ester hydrolysis:}
+\begin{itemize}
+\item Acidic: \ce{RCOOR + H2O <=>[H+] RCOOH + R-OH}
+\item Basic (saponification): \ce{RCOOR + NaOH -> RCOONa + R-OH}
+\end{itemize}
+
+\textbf{Amide hydrolysis:}
+\begin{itemize}
+\item Acidic: \ce{RCONH2 + H2O + HCl ->[heat] RCOOH + NH4Cl}
+\item Basic: \ce{RCONH2 + NaOH ->[heat] RCOONa + NH3 ^}
+\end{itemize}
+
+\subsection{Named reactions and tests}
+
+\subsubsection{Silver mirror reaction (Tollens' test)}
+
+\textbf{Purpose:} Test for aldehydes; distinguishes aldehydes from ketones.
+
+\textbf{Reagent:} Tollens' reagent - ammoniacal silver nitrate solution \ce{[Ag(NH3)2]+}
+
+\textbf{Principle:} Aldehydes are oxidized to carboxylic acids while silver ions are reduced to metallic silver, forming a silver mirror on the test tube.
+
+\textbf{Preparation of reagent:}
+\begin{itemize}
+\item \ce{AgNO3 + NaOH -> AgOH v + NaNO3}
+\item \ce{AgOH + 2NH3 -> [Ag(NH3)2]OH} (soluble complex)
+\end{itemize}
+
+\textbf{Reaction with aldehyde:}
+\begin{itemize}
+\item \ce{RCHO + 2[Ag(NH3)2]+ + 2OH- -> RCOO- + 2Ag v + 4NH3 + H2O}
+\item Formaldehyde: \ce{HCHO + 4[Ag(NH3)2]+ + 4OH- -> CO3^2- + 4Ag v + 8NH3 + 2H2O}
+\item Glucose (reducing sugar): \ce{C6H12O6 + 2[Ag(NH3)2]+ + 2OH- -> C6H12O7 + 2Ag v + 4NH3}
+\end{itemize}
+
+\textbf{Observation:} Silver mirror forms on the inner surface of the test tube (positive test).
+
+\textbf{Note:} Ketones do not give this reaction. Some $\alpha$-hydroxy ketones may give weakly positive results.
+
+\subsubsection{Fehling's test (Benedict's test)}
+
+\textbf{Purpose:} Test for reducing sugars and aldehydes.
+
+\textbf{Reagent:} Fehling's solution (mixture of Fehling's A and B)
+\begin{itemize}
+\item Fehling's A: Copper(II) sulfate solution \ce{CuSO4}
+\item Fehling's B: Alkaline sodium potassium tartrate solution (Rochelle salt)
+\end{itemize}
+
+\textbf{Principle:} Aldehydes reduce Cu$^{2+}$ (blue) to Cu$_2$O (red-brown precipitate).
+
+\textbf{Reaction:}
+\begin{itemize}
+\item \ce{RCHO + 2Cu^2+ + 5OH- ->[heat] RCOO- + Cu2O v + 3H2O}
+\item With glucose: \ce{C6H12O6 + 2Cu^2+ + 5OH- -> C6H12O7 + Cu2O v + 3H2O}
+\end{itemize}
+
+\textbf{Observation:} Blue solution turns to red-brown precipitate of cuprous oxide.
+
+\textbf{Benedict's reagent:} Similar test using copper citrate complex instead of tartrate.
+
+\subsubsection{Iodine clock reaction}
+
+\textbf{Purpose:} Demonstration of reaction kinetics and reaction mechanisms.
+
+\textbf{Principle:} A sudden color change occurs after a predictable time period, demonstrating the relationship between reaction rate and concentration.
+
+\textbf{Common version (Landolt reaction):}
+\begin{itemize}
+\item Reaction A (slow): \ce{H2O2 + 2I- + 2H+ -> I2 + 2H2O}
+\item Reaction B (fast): \ce{I2 + 2S2O3^2- -> 2I- + S4O6^2-}
+\item When thiosulfate is consumed, free iodine reacts with starch indicator
+\item \ce{I2 + starch -> blue complex}
+\end{itemize}
+
+\textbf{Alternative version (Dushman reaction):}
+\begin{itemize}
+\item \ce{IO3- + 3HSO3- -> I- + 3SO4^2- + 3H+} (slow)
+\item \ce{IO3- + 5I- + 6H+ -> 3I2 + 3H2O} (fast, when HSO$_3^-$ depleted)
+\end{itemize}
+
+\textbf{Observation:} Solution remains colorless for a fixed time, then suddenly turns deep blue.
+
+\textbf{Variables affecting clock time:}
+\begin{itemize}
+\item Concentration of reactants
+\item Temperature
+\item Presence of catalysts
+\end{itemize}
+
+\subsubsection{Biuret test}
+
+\textbf{Purpose:} Test for proteins and peptide bonds; detects presence of peptide linkages.
+
+\textbf{Reagent:} Biuret reagent (copper sulfate in alkaline solution)
+\begin{itemize}
+\item \ce{CuSO4} in dilute \ce{NaOH} solution
+\end{itemize}
+
+\textbf{Principle:} Peptide bonds form a colored complex with Cu$^{2+}$ ions in alkaline solution.
+
+\textbf{Reaction:} Copper ions coordinate with nitrogen atoms of peptide bonds, forming a violet-purple complex.
+
+\textbf{Named after:} Biuret \ce{H2N-CO-NH-CO-NH2}, the simplest compound that gives this test.
+
+\textbf{Observation:}
+\begin{itemize}
+\item Negative (no protein): Blue color (from Cu$^{2+}$ ions)
+\item Positive (protein present): Violet to purple color
+\item Intensity depends on number of peptide bonds
+\end{itemize}
+
+\textbf{Requirements:}
+\begin{itemize}
+\item At least two peptide bonds required for positive test
+\item Single amino acids do not give positive result
+\item Dipeptides give weak positive result
+\item Tripeptides and proteins give strong positive result
+\end{itemize}
+
+\textbf{Application:}
+\begin{itemize}
+\item Qualitative test for proteins
+\item Semi-quantitative determination of protein concentration
+\item Used in biochemistry and food analysis
+\end{itemize}
+
+\subsubsection{Lucas test}
+
+\textbf{Purpose:} Distinguish between primary, secondary, and tertiary alcohols.
+
+\textbf{Reagent:} Lucas reagent (anhydrous \ce{ZnCl2} in concentrated \ce{HCl})
+
+\textbf{Principle:} Alcohols react with HCl in presence of \ce{ZnCl2} to form alkyl chlorides (insoluble, appears as cloudiness).
+
+\textbf{Reactions:}
+\begin{itemize}
+\item \ce{ROH + HCl ->[ZnCl2] RCl + H2O}
+\item Rate: Tertiary > Secondary > Primary
+\end{itemize}
+
+\textbf{Observations:}
+\begin{itemize}
+\item Tertiary alcohol: Immediate cloudiness (turbidity)
+\item Secondary alcohol: Cloudiness within 5-10 minutes
+\item Primary alcohol: No reaction at room temperature
+\end{itemize}
+
+\subsubsection{Diazotization reaction}
+
+\textbf{Purpose:} Formation of diazonium salts from primary aromatic amines.
+
+\textbf{Reagent:} Sodium nitrite (\ce{NaNO2}) and dilute \ce{HCl} at 0-5$^\circ$C
+
+\textbf{Reaction:}
+\begin{itemize}
+\item \ce{C6H5NH2 + NaNO2 + 2HCl ->[cold] C6H5N2+Cl- + NaCl + 2H2O}
+\item Temperature must be kept low to prevent decomposition
+\end{itemize}
+
+\textbf{Applications:}
+\begin{itemize}
+\item Azo dye synthesis (coupling with phenols or aromatic amines)
+\item Sandmeyer reaction (replacement of diazonium group)
+\item Gattermann reaction
+\end{itemize}
+
+\subsubsection{Friedel-Crafts reactions}
+
+\textbf{Friedel-Crafts alkylation:}
+\begin{itemize}
+\item \ce{C6H6 + RCl ->[AlCl3] C6H5R + HCl}
+\item Introduces alkyl group onto aromatic ring
+\item Catalyst: \ce{AlCl3} or \ce{FeCl3}
+\item Problem: Polyalkylation and rearrangement
+\end{itemize}
+
+\textbf{Friedel-Crafts acylation:}
+\begin{itemize}
+\item \ce{C6H6 + RCOCl ->[AlCl3] C6H5COR + HCl}
+\item Introduces acyl group onto aromatic ring
+\item More controlled than alkylation (no polyacylation)
+\item Forms ketones
+\end{itemize}
+
+\subsubsection{Kolbe's reaction (Kolbe-Schmitt reaction)}
+
+\textbf{Purpose:} Synthesis of salicylic acid from phenol.
+
+\textbf{Reaction:}
+\begin{itemize}
+\item \ce{C6H5OH + NaOH -> C6H5ONa + H2O}
+\item \ce{C6H5ONa + CO2 ->[heat, pressure] C6H4(OH)COONa} (sodium salicylate)
+\item \ce{C6H4(OH)COONa + HCl -> C6H4(OH)COOH + NaCl} (salicylic acid)
+\end{itemize}
+
+\textbf{Conditions:} High pressure (5-7 atm), 125-130$^\circ$C
+
+\textbf{Application:} Industrial production of aspirin (acetylsalicylic acid)
+
+\subsubsection{Cannizzaro reaction}
+
+\textbf{Purpose:} Disproportionation of aldehydes lacking $\alpha$-hydrogen.
+
+\textbf{Principle:} In strong base, one aldehyde molecule is oxidized to carboxylate, another is reduced to alcohol.
+
+\textbf{Reaction:}
+\begin{itemize}
+\item \ce{2RCHO + NaOH ->[no alpha-H] RCOONa + RCH2OH}
+\item Example: \ce{2C6H5CHO + NaOH -> C6H5COONa + C6H5CH2OH}
+\item Formaldehyde: \ce{2HCHO + NaOH -> HCOONa + CH3OH}
+\end{itemize}
+
+\textbf{Requirement:} Aldehyde must lack $\alpha$-hydrogen atoms.
+
+\subsubsection{Haloform reaction}
+
+\textbf{Purpose:} Test for methyl ketones; produces haloform.
+
+\textbf{Reagent:} Halogen (\ce{I2}, \ce{Br2}, or \ce{Cl2}) in alkaline solution
+
+\textbf{Reaction:}
+\begin{itemize}
+\item \ce{CH3COR + 3I2 + 4NaOH -> RCOONa + CHI3 v + 3NaI + 3H2O}
+\item Iodoform (\ce{CHI3}): Yellow precipitate with characteristic odor
+\end{itemize}
+
+\textbf{Positive test:}
+\begin{itemize}
+\item Methyl ketones: \ce{R-CO-CH3}
+\item Acetaldehyde: \ce{CH3CHO}
+\item Ethanol: \ce{CH3CH2OH} (oxidized to acetaldehyde first)
+\end{itemize}
+
+\textbf{Iodoform test:} Specific for compounds with \ce{CH3CO-} or \ce{CH3CH(OH)-} structure.
+
 \section{Hydrocarbons and their Halogen derivatives}
 
 \section{Alicyclic compounds and aromatic compounds}