Std. 11
Chemistry

Chemistry studies matter, its composition, properties and the changes it undergoes.

The laws of conservation of mass, definite proportions and multiple proportions describe regular patterns in chemical combination.

One mole contains 6.022 × 10²³ specified particles. It connects microscopic particles with measurable laboratory quantities.

n = m/M
Number of moles equals given mass divided by molar mass.

It identifies what substances are present and determines how much of a substance is present.

It answers the question: which ions or substances are present?

It determines the amount or concentration of a component in a sample.

Accuracy concerns closeness to the true value; precision concerns agreement among repeated measurements.

A solid insoluble in a liquid can be separated using a porous medium.

A dissolved solid can be obtained as crystals by controlling concentration and temperature.

A liquid mixture can be separated using differences in volatility or boiling point.

Components move at different rates between stationary and mobile phases, allowing separation and identification.

Protons and neutrons are in the nucleus; electrons occupy the region outside the nucleus.

Z = number of protons
A = protons + neutrons

Electrons occupy permitted energy levels in the Bohr model of hydrogen-like atoms.

Electrons are described by orbitals and quantum numbers rather than fixed circular paths.

Atoms form chemical bonds to reach more stable arrangements of electrons and lower-energy states.

Electrons are transferred and oppositely charged ions are held by electrostatic attraction.

Atoms share electron pairs. Single, double and triple bonds involve one, two and three shared pairs respectively.

Electron pairs around a central atom arrange themselves to minimise repulsion, helping predict molecular shape.

Oxidation can be understood as loss of electrons, increase in oxidation number or addition of oxygen in suitable reactions.

Reduction can be understood as gain of electrons, decrease in oxidation number or removal of oxygen in suitable reactions.

An oxidising agent causes oxidation and is itself reduced; a reducing agent causes reduction and is itself oxidised.

It is a bookkeeping value assigned to atoms to track electron transfer in redox processes.

The physical and chemical properties of elements are periodic functions of their atomic numbers.

Periods are horizontal rows and groups are vertical columns. Elements in a group often show related valence-electron patterns.

Atomic radius, ionisation enthalpy, electron gain tendency and electronegativity show systematic variations.

The s, p, d and f blocks are associated with the subshell receiving the differentiating electron.

Group 1 elements have one valence electron and commonly form +1 ions.

Group 2 elements have two valence electrons and commonly form +2 ions.

Group 1 and Group 2 metals generally become more reactive down their groups because their outer electrons are removed more easily.

Compounds such as NaOH, Na₂CO₃, CaO and CaCO₃ have important laboratory and industrial uses.

Boron and its group members show characteristic trends in oxidation states, bonding and metallic character.

Carbon, silicon and other members display important catenation and bonding behaviour.

Nitrogen and phosphorus are important non-metals with several oxidation states and compounds.

Borax, silicones and ammonia illustrate important chemistry of these groups.

Attractive forces between particles help explain why solids, liquids and gases behave differently.

PV = constant (Boyle)
V/T = constant (Charles)
P/T = constant (Gay-Lussac)

PV = nRT

Gas pressure arises from molecular collisions with container walls, and average kinetic energy increases with absolute temperature.

Adsorption is accumulation of a substance at the surface of another substance; it differs from absorption, which involves the bulk.

Physical adsorption involves weaker forces, while chemisorption involves stronger chemical interaction with the surface.

A catalyst changes the rate of a reaction without being consumed in the overall reaction.

A colloid contains dispersed particles larger than molecules but small enough to remain dispersed for long periods.

In a reversible reaction at equilibrium, forward and reverse reactions continue but occur at equal rates.

For a reaction at equilibrium, concentrations enter the equilibrium expression according to their stoichiometric powers.

Kc = products / reactants
The exact expression uses equilibrium concentrations raised to their stoichiometric coefficients.

When an equilibrium system is disturbed, it shifts in a direction that tends to oppose the disturbance.

It deals with changes occurring in atomic nuclei rather than ordinary rearrangements of valence electrons.

Unstable nuclei can spontaneously emit radiation as they move toward greater stability.

N = N₀(1/2)^(t/t½)
Half-life is the time required for half of a radioactive sample to decay.

Fission splits a heavy nucleus; fusion combines light nuclei under suitable extreme conditions.

It studies carbon compounds, especially their structures, reactions and characteristic functional groups.

Carbon forms strong carbon-carbon bonds, allowing chains, branches and rings.

A functional group is an atom or group of atoms responsible for characteristic reactions of an organic compound.

Systematic naming identifies the parent structure, substituents, positions and principal functional group.

Hydrocarbons contain only carbon and hydrogen.

Alkanes contain only single C–C bonds and are saturated hydrocarbons.

Alkenes contain at least one C=C bond; alkynes contain at least one C≡C bond.

Aromatic compounds contain special delocalised π-electron systems; benzene is the simplest important example.

Drugs are chemical substances designed to produce desired biological effects, such as reducing symptoms or treating disease.

They contain parts that interact with water and parts that interact with oily dirt, helping remove grease.

Polymers are very large molecules formed from repeating structural units called monomers.

Everyday chemical products can have environmental consequences, so safe use, disposal and sustainable alternatives matter.