10th Class Chemistry: Chemical Reactions

• Chemistry is the study of matter, its properties, and how it changes.
• Class 10 chemistry typically covers chemical reactions and equations, acids, bases and salts, metals and nonmetals, carbon compounds, and the periodic classification of elements.

Chemical Reactions and Equations

• A chemical reaction involves the rearrangement of atoms and molecules, forming new substances.
• Reactants are the substances participating in a chemical reaction.
• Products are the new substances formed as a result of the reaction.
• A balanced chemical equation features the same number of atoms of each element on both sides, obeying the law of conservation of mass.
• Balancing chemical equations involves adjusting coefficients in front of the chemical formulas.
• Combination reactions occur when two or more reactants combine into a single product.
• Decomposition reactions involve a single reactant breaking down into two or more products.
• Displacement reactions occur when a more reactive element displaces a less reactive element from its compound.
• Double displacement reactions involve the exchange of ions between two compounds, forming two new compounds.
• Precipitation reactions are double displacement reactions where one product is an insoluble solid (precipitate).
• Oxidation is the loss of electrons or an increase in oxidation state.
• Reduction is the gain of electrons or a decrease in oxidation state.
• Redox reactions involve both oxidation and reduction processes occurring simultaneously.
• Corrosion occurs when metals are gradually eaten away by air, moisture, or chemicals on their surface.
• Rancidity is the oxidation of fats and oils in foods, leading to unpleasant taste and odor.
• Rancidity can be prevented by antioxidants, nitrogen packing, refrigeration, and airtight storage.

Acids, Bases, and Salts

• Acids produce hydrogen ions (H⁺) when dissolved in water.
• Acids taste sour.
• Acids turn blue litmus paper red.
• Acids react with metals to form hydrogen gas.
• Bases produce hydroxide ions (OH⁻) when dissolved in water.
• Bases taste bitter and feel soapy.
• Bases turn red litmus paper blue.
• Neutralization is the reaction between an acid and a base, forming salt and water.
• Indicators change color in the presence of acids or bases.
• Litmus, methyl orange, and phenolphthalein are common acid-base indicators.
• The pH scale measures the acidity or basicity of a solution.
• pH values range from 0 to 14.
• pH < 7 indicates an acidic solution.
• pH = 7 indicates a neutral solution.
• pH > 7 indicates a basic solution.
• Strong acids and bases completely dissociate in water.
• Weak acids and bases partially dissociate in water.
• Salts are ionic compounds formed by the neutralization of an acid with a base.
• Salts can be acidic, basic, or neutral, depending on the strengths of the acid and base that formed them.
• Common salt (NaCl) is used in food and as a raw material for producing other chemicals.
• Sodium hydroxide (NaOH) is a strong base used in soap and paper manufacturing.
• Bleaching powder (CaOCl₂) is used as a disinfectant and bleaching agent.
• Baking soda (NaHCO₃) is used in baking and as an antacid.
• Washing soda (Na₂CO₃·10H₂O) is used as a cleaning agent and in the manufacture of glass and paper.
• Plaster of Paris (CaSO₄·0.5H₂O) is used for making casts and molds.

Metals and Nonmetals

• Metals are typically hard, lustrous, malleable, ductile, and good conductors of heat and electricity.
• Nonmetals are typically soft, dull, brittle, and poor conductors of heat and electricity.
• Metals are electropositive, tending to lose electrons to form positive ions (cations).
• Nonmetals are electronegative, tending to gain electrons to form negative ions (anions).
• Metals react with oxygen to form basic oxides.
• Nonmetals react with oxygen to form acidic or neutral oxides.
• Metals react with acids to produce hydrogen gas.
• The reactivity series arranges metals in order of their decreasing reactivity.
• Ionic compounds are formed by the transfer of electrons between metals and nonmetals.
• Covalent compounds are formed by the sharing of electrons between nonmetals.
• Metallic bonding involves the delocalization of electrons in a "sea" around positively charged metal ions.
• Minerals are naturally occurring inorganic substances in the Earth's crust.
• Ores are minerals from which metals can be extracted economically.
• Metallurgy is the process of extracting metals from their ores.
• Roasting involves heating the ore strongly in the presence of excess air.
• Calcination involves heating the ore strongly in the absence of air.
• Reduction involves the removal of oxygen from the metal oxide.
• Refining is the purification of metals.
• Corrosion is the process by which metals are gradually eaten away by air, moisture, or chemicals.
• Rusting is the corrosion of iron, forming iron oxide (rust).
• Corrosion can be prevented by galvanization, painting, electroplating, and alloying.
• Alloys are homogeneous mixtures of two or more metals or a metal and a nonmetal.
• Alloys often have improved properties compared to their constituent metals.
• Steel is an alloy of iron and carbon.
• Brass is an alloy of copper and zinc.
• Bronze is an alloy of copper and tin.

Carbon Compounds

• Carbon is versatile and forms a large number of compounds due to its tetravalency and catenation.
• Catenation is the ability of carbon atoms to form long chains and rings with other carbon atoms.
• Hydrocarbons are organic compounds composed of carbon and hydrogen atoms.
• Saturated hydrocarbons contain only single bonds between carbon atoms (alkanes).
• Unsaturated hydrocarbons contain double or triple bonds between carbon atoms (alkenes and alkynes).
• Alkanes have the general formula CₙH₂ₙ₊₂.
• Alkenes have the general formula CₙH₂ₙ.
• Alkynes have the general formula CₙH₂ₙ₋₂.
• Functional groups are atoms or groups of atoms that determine the properties of organic compounds.
• Alcohols contain the -OH functional group.
• Aldehydes contain the -CHO functional group.
• Ketones contain the -CO- functional group.
• Carboxylic acids contain the -COOH functional group.
• Isomers are compounds with the same molecular formula but different structural formulas.
• A homologous series consists of organic compounds with the same functional group and similar chemical properties.
• Nomenclature is the system of naming organic compounds.
• IUPAC nomenclature provides a standardized way to name organic compounds.
• Combustion involves burning carbon compounds in oxygen to produce carbon dioxide and water.
• Oxidation is the addition of oxygen or removal of hydrogen.
• Addition reactions involve the addition of atoms or groups of atoms to unsaturated hydrocarbons.
• Substitution reactions involve the replacement of one atom or group of atoms with another.
• Ethanol is an alcohol used in alcoholic beverages and as a solvent.
• Ethanoic acid (acetic acid) is a carboxylic acid found in vinegar.
• Soaps are sodium or potassium salts of long-chain carboxylic acids.
• Detergents are synthetic cleaning agents that work in hard water.
• Micelles are spherical aggregates of soap or detergent molecules in water.

Periodic Classification of Elements

• Elements are arranged in the periodic table based on their atomic number and electronic configuration.
• Mendeleev's periodic table arranged elements based on their atomic mass and properties.
• The modern periodic table arranges elements based on their atomic number.
• Groups are vertical columns with elements having similar valence electron configurations and chemical properties.
• Periods are horizontal rows representing different energy levels or electron shells.
• Metals are located on the left side of the periodic table.
• Nonmetals are located on the right side of the periodic table.
• Metalloids (semimetals) have properties intermediate between metals and nonmetals.
• Alkali metals are group 1 elements, highly reactive metals.
• Alkaline earth metals are group 2 elements, reactive metals.
• Halogens are group 17 elements, highly reactive nonmetals.
• Noble gases are group 18 elements, inert gases with full valence shells.
• Atomic size generally decreases across a period (left to right) and increases down a group.
• Ionization energy is the energy required to remove an electron from an atom in its gaseous state.
• Ionization energy generally increases across a period and decreases down a group.
• Electron affinity is the energy change when an electron is added to an atom in its gaseous state.
• Electronegativity is a measure of the ability of an atom to attract electrons in a chemical bond.
• Electronegativity generally increases across a period and decreases down a group.
• Metallic character generally decreases across a period and increases down a group.

Understand chemical reactions, equations, reactants, and products. Learn to balance equations and explore combination, decomposition, and displacement reactions. This lesson covers key concepts in Class 10 chemistry.