chem chapter 1 and 2

Chemical Reaction

A process that occurs when one or more reactants are changed into one or more products. The constituent atoms of the reactants are rearranged, resulting in the formation of various substances as products.

Chemical Change

A change where one or more new substances with new physical and chemical properties are formed.

Physical Change

A change in color or state occurs, but no new substance is formed (e.g., water changing to steam).

Word Equation

A chemical reaction expressed in words rather than chemical formulas. It helps identify the reactants and products in a chemical reaction.

Chemical Equation

Representation of a chemical reaction in terms of symbols and chemical formulae of the reactants and products.

Symbol

A chemical code for an element. Each element has a one or two-letter atomic symbol, which is usually the abbreviated form of its name.

Valency

The combining capacity of an element. It can be considered as the number of electrons lost, gained or shared by an atom when it combines with another atom to form a molecule.

Law of Conservation of Mass

No atoms can be created or destroyed in a chemical reaction, so the number of atoms for each element on the reactants side must balance the number of atoms on the products side. The total mass of products equals the total mass of reactants.

Balanced Chemical Equation

A chemical equation in which the number of atoms of each element on the reactants side is equal to that of the products side.

Coefficient

A numerical value added to the front of a chemical symbol or formula. It indicates the number of atoms or molecules of the material involved in the process.

Combination Reaction

Two elements or one element and one compound or two compounds combine to give one single product.

Decomposition Reaction

A single reactant decomposes on the application of heat, light, or electricity to give two or more products.

Thermolysis

Decomposition reaction that requires heat (thermal decomposition).

Photolysis

Decomposition reaction that requires light (photolytic decomposition).

Electrolysis

Decomposition reaction that requires electricity (electrolytic decomposition).

Displacement Reaction

A more reactive element displaces a less reactive element from its compound or solution.

Double Displacement Reaction

An exchange of ions between the reactants takes place to give new products.

Precipitation Reaction

A type of double displacement reaction where an insoluble compound (precipitate) is formed.

Precipitate

An insoluble compound that forms when two solutions containing soluble salts are combined.

Redox Reaction

A reaction that occurs when the oxidation states of the substrate change. Oxidation and reduction take place simultaneously.

Oxidation

Loss of electrons, gain of oxygen, loss of hydrogen, or increase in oxidation state.

Reduction

Gain of electrons, loss of oxygen, gain of hydrogen, or decrease in oxidation state.

Oxidising Agent

A substance that oxidises another substance and itself gets reduced.

Reducing Agent

A substance that reduces another substance and itself gets oxidised.

Exothermic Reaction

A reaction where heat is evolved during the reaction. Most combination reactions are exothermic.

Endothermic Reaction

A reaction where heat is required to carry out the reaction. Most decomposition reactions are endothermic.

Corrosion

Gradual deterioration of a material, usually a metal, by the action of moisture, air or chemicals in the surrounding environment.

Rusting

A specific type of corrosion affecting iron, where iron reacts with oxygen and moisture to form rust (Fe₂O₃.xH₂O).

Rancidity

The oxidation of fats and oils in food that is kept for a long time. It gives foul smell and bad taste to food.

(s)

Symbol indicating solid state in chemical equations.

(l)

Symbol indicating liquid state in chemical equations.

(g)

Symbol indicating gaseous state in chemical equations.

(aq)

Symbol indicating aqueous solution in chemical equations.

(↑)

Symbol indicating gas produced in the reaction.

(↓)

Symbol indicating precipitate formed in the reaction.

Evolution of Gas

An observation that indicates a chemical reaction is occurring.

Change in Temperature

An observation that indicates a chemical reaction is occurring.

Formation of Precipitate

An observation that indicates a chemical reaction is occurring.

Change in Color

An observation that indicates a chemical reaction is occurring.

Change of State

An observation that indicates a chemical reaction is occurring.

Acid

A substance that tastes sour in water, turns blue litmus red, and neutralises the bases. Any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance.

Base

A material that reacts with an acid to produce just water and salt. A substance whose aqueous solution tastes bitter, turns red litmus blue, or neutralises acids. A molecule or ion able to accept a hydrogen ion from an acid.

Salt

A neutral material that has no effect on litmus in an aqueous solution. Formed when hydrogen ions are replaced by a metal or an ammonium ion in an acid. A combination of an anion of an acid and a cation of a base.

Ionisable Compound

A compound that, when dissolved in water or in its molten state, dissociates into ions almost entirely. Examples: NaCl, HCl, KOH.

Non-Ionisable Compound

A compound that does not dissociate into ions when dissolved in water or in its molten state. Examples: glucose, acetone.

Arrhenius Acid

When dissolved in water, dissociates to give H+ (aq) or H3O+ ion.

Arrhenius Base

When dissolved in water, dissociates to give OH− ion.

Bronsted Acid

An H+ (aq) ion donor.

Bronsted Base

An H+ (aq) ion acceptor.

Conjugate Acid

The species formed when a Bronsted base accepts a proton.

Conjugate Base

The species formed when a Bronsted acid donates a proton.

Indicator

A chemical substance which shows a change in its physical properties, mainly colour or odour, when brought in contact with an acid or a base.

Litmus

An indicator that is purple in neutral solution, red in acidic solution, and blue in basic solution.

Methyl Orange

An indicator that is orange in neutral solution, red in acidic solution, and yellow in basic solution.

Phenolphthalein

An indicator that is colourless in neutral and acidic solutions, and pink in basic solution.

Neutralisation Reaction

A reaction that occurs when an acid reacts with a base, producing salt and water as the end products.

Alkali

An aqueous solution of a base (mainly metallic hydroxides). It dissolves in water and dissociates to give OH− ion. All alkalis are bases, but not all bases are alkalis.

Hydronium Ion

Ion formed when a hydrogen ion accepts a lone pair of electrons from the oxygen atom of a water molecule, forming a coordinate covalent bond. Formula: H3O+.

Dilution

The process of reducing the concentration of a solution by adding more solvent (usually water) to it. It is a highly exothermic process.

Strong Acid or Base

When all molecules of a given amount of an acid or base dissociate completely in water to furnish their respective ions.

Weak Acid or Base

When only a few of the molecules of a given amount of an acid or base dissociate in water to furnish their respective ions.

Dilute Acid

Contains less number of H+(aq) ions per unit volume.

Concentrated Acid

Contains more number of H+(aq) ions per unit volume.

Universal Indicator

Has a pH range from 0 to 14 that indicates the acidity or alkalinity of a solution.

pH

pH = −log10[H+]. The pH scale ranges from 0 to 14. If pH < 7 → acidic solution, If pH > 7 → basic solution, pH = 7 → neutral solution.

Common Salt

Sodium Chloride (NaCl) - referred to as common salt because it's used all over the world for cooking.

Family of Salts

Salts having the same cation or anion belong to the same family. For example, NaCl, KCl, LiCl.

Chlor-alkali Process

Process of electrolysis of brine (solution of common salt, NaCl). At anode: Cl2 is released, At cathode: H2 is released, Sodium hydroxide remains in the solution.

Sodium Hydroxide

Chemical formula: NaOH. Also known as caustic soda. A strong base prepared by chlor-alkali process.

Bleaching Powder

Chemical formula: Ca(OCl)Cl or CaOCl2. Prepared by reacting chlorine gas with dry slaked lime. Used as bleaching agent, oxidizing agent, and disinfectant.

Baking Soda

Chemical name: Sodium hydrogen carbonate. Chemical formula: NaHCO3. Used to reduce acidity in stomach, acts as antacid, and used in washing as water softener.

Washing Soda

Chemical name: Sodium carbonate decahydrate. Chemical formula: Na2CO3.10H2O. Used in glass, soap and paper industries, softening of water, and as domestic cleaner.

Solvay Process

Industrial process for preparation of sodium hydrogen carbonate (baking soda) and sodium carbonate (washing soda).

Water of Crystallisation

The water that combines with salt when certain salts form crystals by combining with a definite proportion of water.

Crystallisation

The process by which a solid forms, in which the atoms or molecules are strongly arranged into a structure known as a crystal.

Plaster of Paris

Chemical formula: CaSO4.½H2O. Obtained by heating gypsum at 100°C. Used for casts in healing fractures. Also known as gypsum plaster.

Gypsum

Chemical formula: CaSO4.2H2O. When heated at 100°C gives Plaster of Paris and water.

Effervescence

Indicates the liberation of CO2 gas when acids react with metal carbonates and bicarbonates.

Acid Anhydrides

Non-metal oxides are referred to as acid anhydrides because they form acids when combined with water.

pH Sensitivity

Plants and animals are sensitive to pH. Crucial life processes happen at specific pH values.

Optimal Soil pH

The pH of soil optimal for the growth of plants or crops is 6.5 to 7.0.

Stomach pH

The pH in our stomach for digestion is 1.5 to 4.0.

Tooth Decay pH

Tooth decay happens when teeth are exposed to acidic environment of pH 5.5 and below.

Physical Property

Any measurable property whose value describes a condition of a physical system. Can be used to characterise transitions between brief states.

Observables

A term used to describe physical qualities or properties that can be measured.

Hard

Property of metals having high tensile strength and resistance to deformation.

Tensile Strength

The resistance of a material to breaking under tension.

Sonorous

Property of metals that produce a typical ringing sound when hit by something.

Malleable

Property of metals that can be beaten into thin sheets.

Ductile

Property of metals that can be drawn into thin wires.

Lustrous

Property of metals having the quality of reflecting light from their surface and can be polished.

Non-Metals

Elements which do not exhibit the properties of metals. Occur as solids, liquids and gases at room temperature.

Brittle

Property of non-metals that break easily when subjected to stress.

Non-malleable

Property of non-metals that cannot be beaten into thin sheets.

Non-ductile

Property of non-metals that cannot be drawn into thin wires.

Non-sonorous

Property of non-metals that do not produce ringing sound when hit.

Metal Oxide

Basic compound formed when metals react with oxygen. Changes red litmus to blue.

Basic Oxides

Metal oxides that typically react with water to form bases or with acids to form salts.

Amphoteric Oxides

Metal oxides which react with both acids as well as bases to form salt and water. Examples: Al2O3, ZnO, PbO, SnO.

Reactivity Series

The arrangement of metals in the descending order of their reactivities. Also known as activity series.