The Indian Certificate of Secondary Education (ICSE) is an examination conducted by the Council for the Indian School Certificate Examination, a private board of school education in India. It has been designed to provide an examination in a course of general education, in accordance with the recommendations of the New Education Policy 1986, through the medium of English.

The examination allows secure suitable representation of governments responsible for schools (which are affiliated to it) in their states or territories. Private candidates are not permitted to appear for this examination.

Candidates appearing for the examination have to study six subjects, with one to three papers in each subject. This makes for a total of eight to eleven papers, depending on the subjects. ICSE results are taken from best five of six subjects out of which English marks is compulsory.


Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

Part I (20 marks): This part consists of compulsory short answer questions, testing knowledge, application and skills relating to elementary/fundamental aspects of the entire syllabus.

Part II (50 marks): This part is divided into three Sections A, B and C. There are six questions in Section A (each carrying 7 marks) and you are required to answer four questions from this Section. There are three questions in Section B (each carrying 6 marks) and you are required to answer two questions from this Section. There are three questions in Section C (each carrying 5 marks) and you are required to answer two questions from this Section. Therefore, you are expected to answer eight questions in Part II.




  1. Role of Physics

(i) Scope of Physics.

(ii) Role of Physics in technology.

(iii) Impact on society.


  1. Units

(i) SI units. Fundamental and derived units (correct symbols for units including conventions for symbols).

(ii) Accuracy and errors in measurement, least count of measuring instruments (and the implications for errors in experimental measurements and calculations).

(iii) Significant figures and order of accuracy with reference to measuring instruments. Powers of 10 and order of magnitude.


  1. Dimensions

(i) Dimensional formula of physical quantities and physical constants like g, h, etc. (from Mechanics only).

(ii) Dimensional equation and its use to check correctness of a formula, to find the relation between physical quantities, to find the dimension of a physical quantity or constant; limitations of dimensional analysis.


  1. Vectors, Scalar Quantities and Elementary Calculus

(i) General Vectors and notation, position and displacement vector.

(ii) Vectors in one dimension, two dimensions and three dimensions, equality of vectors and null vector. Vector operations (addition, subtraction and multiplication of vectors including use of unit vectors iˆ, jˆ, kˆ); parallelogram and triangle law of vector addition.

(iii) Resolution and components of like vectors in a plane (including rectangular components), scalar (dot) and vector (cross) products.

(iv) Elementary Calculus: differentiation and integration as required for physics topics in Classes XI and XII. No direct question will be asked from this subunit in the examination.


  1. Dynamics

(i) Cases of uniform velocity, equations of uniformly accelerated motion and applications including motion under gravity (close to surface of the earth) and motion along a smooth inclined plane.

(ii) Relative velocity. 

(iii) Projectile motion.

(iv) Newton’s laws of motion and simple applications. Elementary ideas on inertial and uniformly accelerated frames of reference. Conservative and non-conservative forces. Conservation of linear momentum, impulse.

(v) Concurrent forces (reference should be made to force diagrams and to the point of application of forces), work done by constant and variable force (Spring force).

(vi) Energy, conservation of energy, power, elastic and inelastic collisions in one and two dimensions.


  1. Friction

(i) Friction in solids: static; sliding; rolling.

(ii) Laws of friction. Co-efficient of friction. Methods to minimise friction.


  1. Circular and Rotational Motion

(i) Uniform Circular Motion, Centripetal acceleration and force, motion on a level and a banked track (smooth as well as rough), a point mass at the end of a light inextensible string moving in a (i) horizontal circle, (ii) vertical circle and a conical pendulum.

(ii) Centre of mass, moment of inertia: rectangular rod; disc; ring; sphere.

(iii) Parallel axis theorem and perpendicular axis theorem; radius of gyration.

(iv) Torque and angular momentum, relation between torque and moment of inertia and between angular momentum and moment of inertia; conservation of angular momentum and applications. Comparisons of linear and rotational motions.


  1. Gravitation

(i) Newton’s law of universal gravitation; gravitational constant (G); gravitational acceleration on surface of the earth (g).

(ii) Relation between G and g; variation of gravitational acceleration above and below the surface of the earth.

(iii) Gravitational field, its range, potential, potential energy and intensity.

(iv) Escape velocity (with special reference to the earth and the moon); orbital velocity and period of a satellite in circular orbit (particularly around the earth).

(v) Geostationary satellites – uses of communication satellites.

(vi) Kepler’s laws of planetary motion.


  1. Fluids

(i) Pressure in a fluid, Pascal’s Law and its applications, buoyancy (Archimedes Principle).

(ii) Equation of continuity of fluid flow and its application, buoyancy, Bernoulli’s principle, (venturimeter, pitot tube, atomizer, dynamic uplift).

(iii) Stream line and turbulent flow, Reynold’s number (derivation not required).

(iv) Viscous drag; Newton’s formula for viscosity, co-efficient of viscosity and its units.

(v) Stoke’s law, terminal velocity of a sphere falling through a fluid or a hollow rigid sphere rising to the surface of a fluid.




  1. Properties of Matter – Temperature

(i) Properties of matter: Solids: elasticity in solids, Hooke’s law, Young modulus and its determination, bulk modulus and modulus of rigidity, work done in stretching a wire, Poisson’s ratio. Liquids: surface tension (molecular theory), drops and bubbles, angle of contact, work done in stretching a surface and surface energy, capillary rise, measurement of surface tension by capillary rise method.

(ii) Gases: kinetic theory of gases: postulates, molecular speeds and derivation of p= ⅓ ρc2, equation of state of an ideal gas pV = nRT (numerical problems not included from gas laws).

(iii) Temperature: kinetic interpretation of temperature (relation between c2 and T); absolute temperature. Law of equipartition of energy (statement only).

(iv) Thermal equilibrium and zeroth law of thermodynamics.


  1. Internal Energy

(i) First law of thermodynamics.

(ii) Isothermal and adiabatic changes in a perfect gas described in terms of curves for PV = constant and PVγ = constant; joule and calorie relation (derivation of PVγ = constant not required).

(iii) Work done in isothermal and adiabatic expansion; principal molar heat capacities; Cp and Cv; relation between Cp and Cv (Cp – Cv = R). Cp and Cv for monatomic and diatomic gasses.

(iv) Second law of thermodynamics, Carnot’s cycle. Some practical applications.

(v) Thermal conductivity; co-efficient of thermal conductivity, Use of good and poor conductors, Searle’s experiment. [Lee’s Disc method is not required]. comparison of thermal and electrical conductivity. Convection with examples.

(vi) Thermal radiation: nature and properties of thermal radiation, qualitative effects of nature of surface on energy absorbed or emitted by it; black body and black body radiation, Stefan’s law (using Stefan’s law to determine the surface temperature of the sun or a star by treating it as a black body); Newton’s law of cooling, Wien’s displacement law, distribution of energy in the spectrum of black body radiation (only qualitative and graphical treatment).




  1. Oscillations

(i) Simple harmonic motion.

(ii) Expressions for displacement, velocity and acceleration.

(iii) Characteristics of simple harmonic motion.

(iv) Relation between linear simple harmonic motion and uniform circular motion.

(v) Kinetic and potential energy at a point in simple harmonic motion.

(vi) Derivation of time period of simple harmonic motion of a simple pendulum, mass on a spring (horizontal and vertical oscillations). 

(vii) Free, forced and damped oscillations (qualitative treatment only). Resonance.


  1. Waves

(i) Transverse and longitudinal waves; relation between speed, wavelength and frequency; expression for displacement in wave motion; characteristics of a harmonic wave; graphical representation of a harmonic wave; amplitude and intensity.

(ii) Sound as a wave motion, Newton’s formula for the speed of sound and Laplace’s correction; variation in the speed of sound with changes in pressure, temperature and humidity; speed of sound in liquids and solids (descriptive treatment only).

(iii) Superposition of waves (interference, beats and standing waves), progressive and stationary waves.

(iv) Laws of vibrations of stretched strings.

(v) Modes of vibration of strings and air columns; resonance.


(vi) Doppler Effect for sound.

Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

There is one paper of 3 hours duration divided into 2 parts.

Part I (20 marks) consists of compulsory short answer questions, testing knowledge, application and skills relating to elementary/fundamental aspects of the entire syllabus.

Part II (50 marks) is divided into 3 Sections, A, B and C. You are required to answer two out of three questions from Section A (each carrying 10 marks), two out of three questions from Section B (each carrying 5 marks) and two out of three questions from Section C (each carrying 10 marks). Therefore, a total of six questions are to be answered in Part II.



  1. Some Basic Concepts of Chemistry

(i) Precision and Accuracy

(ii) Dimensional Analysis

(iii) The concept of atoms having fixed properties in explaining the laws of chemical combination.

(iv) Atomic and isotopic masses.

(v) Chemical equivalents, volumetric calculations in terms of normality. C = 12.00 should be taken as a standard for expressing atomic masses.

(vi) Relative molecular mass and mole. The following methods may be considered for the determination of relative molecular masses for the gases: the molar volume method; Victor Meyer’s method (experimental details not required).

(vii) Chemical reaction – Stoichiometric calculations based on mass-mass, mass-volume and volume-volume relationships.


  1. Atomic Structure

(i) Electrons, Protons and Neutrons as fundamental particles, their charges and masses.

(ii) Rutherford’s nuclear model based on the scattering experiment.

(iii) Bohr’s atomic model.

(iv) Atomic structure: wave mechanical model- a simple mathematical treatment. Quantum numbers; shape, size and orientation of s, p and d orbitals only (No derivation). Hund’s rule of maximum multiplicity. Pauli’s exclusion principle, Aufbau principle, electronic configuration of elements in terms of s, p, d, f subshells.


  1. Periodic Table

(i) Atomic number (Proton number) as the basis for classification of the elements in the Periodic Table. IUPAC nomenclature for elements with Z > 100.

(ii) Extra nuclear structure as the basis of periodicity. Some idea of the following: ionisation enthalpy, electron gain enthalpy, atomic radius, atomic volume, electronegativity, etc must be given. The periodicity of electronic structure leading to the periodicity of elements e.g. the relative ease of ionisation of elements. 

(iii) Periodicity of elements with reference to s, p, d and f block elements.


  1. Chemical Bonding

Kossel-Lewis approach to Chemical Bonding.


Electrovalent Bond

(i) Electrovalent or ionic bond e.g formation of NaCl, Li2O, MgO, CaO, MgF2, and Na2S.

(ii) Factors influencing the formation of ionic bond, e.g electron gain enthalpy, ionisation enthalpy, lattice energy and electronegativity.

(iii) The relation between the ionic bonding and Periodic Table.

(iv) Variable electrovalency and its causes.


Covalent Bond

(i) Covalent bond, sigma and pi bonds e.g. formation of ammonia, nitrogen, ethene, ethyne, and carbon dioxide. Resonance.

(ii) Variable valency: chlorine exhibits the valency of 1,3,5 & 7.

(iii) Deviation from Octet rule and Fajan’s rules.

(iv) Co-ordinate or dative covalent bond, e.g. formation of oxy-acids of chlorine.

(v) Hydrogen bonding: its essential requirements, the examples of hydrogen fluoride, water (ice), alcohol, etc may be considered.

(vi) Metallic bonding, van der Waals’ forces.

(vii) Valence Shell Electron Pair Repulsion Theory; Hybridization and shapes of molecules: hybridization involving s, p and d orbitals only; sigma and pi bonds.

(viii) Molecular orbital theory, Qualitative treatment of homonuclear diatomic molecules of first two periods (Hydrogen to Neon). Energy level diagrams, bonding, antibonding molecular orbitals, bond order, paramagnetism of O2 molecule. Relative stabilities of O2, O2-, O22-, O2+ and N2, N2+, N2-, N22-.


  1. The Gaseous State

(i) The gas laws, kinetic theory treated qualitatively.

(ii) PV = nRT or PV= (w/M)RT and the application of this equation of state. 

(iii) Non ideal behaviour of gases and van der Waals’ equation.

(iv) Dalton’s law, Avogadro’s constant, the mole, Graham’s law of diffusion, simple numerical problems on the above.


  1. Surface Chemistry

(i) Adsorption

(ii) Colloidal State: Preparation and properties of colloids, both lyophilic and lyophobic colloids. Precipitation as evidence that the colloidal particles are charged. Idea of gold number is required, but application of gold number is not required. The importance of large surface area in adsorption should also be appreciated.

(iii) Chromatography


  1. Chemical Kinetics

Rate of a chemical reaction, basic idea of order and molecularity of a reaction.


  1. Chemical Energetics

(i) Introduction.

(ii) First law of Thermodynamics and its mathematical statement.

(iii) Ideas about Heat, Work and Energy.

(iv) Second law of thermodynamics – Reversible and irreversible changes, isobaric, isochoric adiabatic processes; Entropy, Free Energy. Spontaneity of a chemical change. ΔG° = -2.303 RT logKeq.

(v) Third Law of Thermodynamics – statement only.

(vi) Thermochemistry:

(a) Definitions.

(b) Constancy in the heat of neutralisation.

(c) Calorific value of a fuel.

(d) Hess’s law of constant heat summation – simple problems based on the above definitions and concepts.




  1. Study of Representative Elements: Group 1, 2, 13, 14, 15

The following should be included: a) Occurrence, (b) Physical State, (c) Electronic Configuration, (d) Atomic and Ionic radii, (e) Common oxidation state, (f) Electropositive / Electronegative character, (g) Ionisation enthalpy, (h) Reducing/oxidising nature, (i) Distinctive behaviour of first member of each group (namely Lithium, Beryllium, Boron, Carbon, Nitrogen), (j) Nature of oxides, hydroxides, hydrides, carbonates, nitrates, chlorides, sulphates, wherever applicable.


  1. Preparation, properties and uses of Compounds of Groups 1, 2, 13, 14, 15

Only brief qualitative treatment is required for preparation. Main emphasis must be given to the chemistry of preparation, chemical properties and uses of the given compounds. Biological importance of magnesium, sodium, calcium and potassium.


Group 1: Sodium chloride, Sodium hydroxide, Sodium carbonate, Sodium bicarbonate, Sodium thiosulphate; Group 2: Magnesium chloride hexahydrate, Calcium oxide, Plaster of Paris, Cement; Group 13: Borax, Borax Bead Test, Boric acid, Alums; Group 14: Carbon monoxide, Carbon dioxide, Silicon dioxide, Silicon carbide, Silicones; Group 15: Oxides of nitrogen, Phosphorus trichloride, Phosphorus pentachloride, Oxoacids of phosphorus.


  1. Redox Reactions

Concept of oxidation and reduction in terms of oxygen, hydrogen, electrons.

Redox reactions – examples.

Oxidation number: Rules for calculation, simple calculations of oxidation state in molecules and ions

Oxidation and reduction in terms of change in oxidation number.

Balancing of redox reactions in acidic and basic medium by oxidation number and ion-electron method.




  1. Introduction to Organic Chemistry

(i) The unique nature of carbon atom and catenation.

(ii) Classification of organic compounds and homologous series.

(iii) Detection of carbon, hydrogen, sulphur, nitrogen and halogen.

(iv) Estimation of carbon, hydrogen, nitrogen, halogens, sulphur and phosphorous.


  1. Isomerism

Definition. Classification of isomerism.

(i) Structural Isomerism.

(ii) Stereo Isomerism.

(a) Geometric isomerism (cis and trans only).

(b) Optical isomerism


  1. Types of Chemical Reactions and their Mechanisms

(i) Substitution, addition and elimination reactions. 

(ii) Homolytic and heterolytic fission.

(iii) Electrophiles and nucleophiles.

(iv) Inductive, mesomeric, electromeric effects and hyperconjugation.

(v) Free radicals and polar mechanisms (in terms of fission of the bonds and formation of the new bonds) including SN1, SN2, E1 and E2 mechanisms.


  1. Aliphatic and Aromatic Hydrocarbons

(i) Alkanes: General methods of preparation, Properties of alkanes.

(ii) Alkenes: general methods of preparation and properties of alkenes.

(iii) Alkynes: methods of preparation (including manufacture), properties and uses of ethyne.

(iv) Benzene: Coal tar as an important source of aromatic compounds; preparation of benzene from sodium benzoate, properties and uses of benzene; resonance model of benzene; directive influence of substituents in the benzene ring.


  1. Applications of Chemicals

(i) In medicine: antipyretics, analgesics, tranquillisers, antiseptics, disinfectants, anti-microbials, anti-fertility drugs, antihistamines, antibiotics, antacids.

(ii) Soaps and Detergents: classification, structure and some important examples.


  1. Environmental Chemistry

(i) Energy: Non-renewable and renewable sources, use of diesel and petrol in trains buses, cars and other vehicles, use of LPG, use of CNG and their role in pollution control.

Future sources of energy – hydrogen, alcohol, fuel cells and bio-fuels. Brief explanation.

Methods of saving energy in homes and institutions – use of energy saving bulbs, solar cooker, bio-gas pipeline.


(ii) Pollution: Environmental pollution: atmospheric pollution and water pollution.

Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

The syllabus is divided into three sections A, B and C. Section A is compulsory. You have a choice of attempting questions from either Section B or Section C.

There is one paper of three hours duration of 100 marks. Section A (80 marks) consists of nine questions. You are required to answer Question 1 (compulsory) and five out of the rest of the eight questions.

In Section B / C (20 marks), you are required to answer two questions out of three from either Section B or Section C.



  1. Mathematical Reasoning

Mathematically acceptable statements. Connecting words / phrases – consolidating the understanding of “if and only if (necessary and sufficient) condition”, “implies”, “and/or”, “implied by”, “and”, “or”, “there exists” and their use through variety of examples related to real life and Mathematics. Validating the statements involving the connecting words, differences between contradiction, converse and contrapositive.


  1. Algebra

(i) Complex Numbers

(ii) Quadratic Equations

(iii) Finite and Infinite Sequences

  • (a) Arithmetic Progression (A.P.)
  • (b) Geometric Progression (G.P.)
  • (c) Harmonic Progression
  • (d) Arithmetico Geometric Series
  • (e) Special sums


(iv) Permutations Combinations

(v) Mathematical induction

  • Using induction to prove various summations and divisibility.

(vi) Binomial Theorem

  • (a) Significance of Pascal’s triangle.
  • (b) Binomial theorem (proof using induction) for positive integral powers
  • (c) Binomial theorem for negative or fractional indices.

(vii) Properties of Binomial Coefficients.


  1. Trigonometry

(i) Angles and Arc lengths

(ii) Trigonometric Functions

(iii) Compound and multiple angles

(iv) Trigonometric Equations


  1. Calculus

(i) Basic Concepts of Relations and Functions

  • (a) Ordered pairs, sets of ordered pairs.
  • (b) Cartesian Product (Cross) of two sets, cardinal number of a cross product.
  • (c) Types of Relations: reflexive, symmetric, transitive and equivalence relation.
  • (d) Binary Operation.
  • (e) Domain, Range and Co-domain of a Relation.
  • (f) Functions


(ii) Differential calculus

  • (a) Limits
  • (b) Continuity
  • (c) Differentiation
  • (d) Application of derivatives


(iii) Integral Calculus


  1. Coordinate Geometry

(i) Basic concepts of Points and their coordinates.

(ii) The straight line

(iii) Circles


  1. Statistics

Measures of central tendency.

Standard deviation – by direct method, short cut method and step deviation method.

Combined mean and standard deviation.




  1. Vectors


  1. Co-ordinate Geometry in 3-Dimensions




  1. Statistics

Median – direct and by using the formula.

Quartiles – direct and by using the formula.

Deciles – direct and by using the formula.

Percentiles – direct and by using the formula.

Mode – graphically, direct method and by using the formula.

Estimation of median/quartiles from Ogives.

NOTE: The following are also required to be covered:


The Median, Quartiles, Deciles and Percentiles of grouped and ungrouped data;

Mode – grouped and ungrouped data; estimation of mode by using graphical method. (Bimodal data not included).


  1. Average Due Date

Zero date.

Equated periods.

Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

Dr. Azam Hussain

Experience: 12 Years

There is one paper of 3 hours duration divided into two parts.

Part I (20 marks) consists of compulsory short answer questions, testing knowledge, application and skills relating to elementary/fundamental aspects of the entire syllabus.

Part II (50 marks) is divided into three Sections A, B and C. You are required to answer two out of three questions from Section A (each carrying 5 marks), two out of three questions from Section B (each carrying 10 marks) and two out of three questions from Section C (each carrying 10 marks). Therefore a total of six questions are to be answered in Part II.



  1. Diversity of Life

(i) Taxonomy and phylogeny, three domains of life; taxonomical hierarchies, binomial nomenclature.

(ii) Five-kingdom classification: salient features, characteristics and examples.

(iii) Morphology and anatomy of different systems of cockroach (digestive, respiratory, circulatory, excretory, nervous and reproductive).



  1. Plant Physiology

(i) Mineral nutrition: macronutrients and micronutrients (role and deficiency symptoms); criteria for essentiality of elements, hydroponics; nitrogen nutrition in plants.

(ii) Plant growth: phases of growth, growth rate, measurement of growth, factors affecting growth, role of growth regulators, seed dormancy and germination, apical dominance, senescence and abscission.

(iii) Photomorphogenesis in plants.


  1. Multicellularity: Structure and Functions of Plants and Animals

(i) Plant Tissues: types of plant tissues: Meristematic: Classification of Meristematic tissue. Permanent Tissues: Structure and function of simple tissues (parenchyma, collenchyma and sclerenchyma) and complex tissues (xylem and phloem), types of vascular bundles.

(ii) Animal Tissues: epithelial; connective; muscular; nervous (location, structure and function).

(iii) Nutrition (human): Calorific value of carbohydrates, proteins and fats, Organs of digestive system (histology of individual organs not required), digestive process and disorders of the digestive system.

(iv) Respiration (human): Organs of respiratory system, breathing mechanism (inspiration and expiration), pulmonary gas exchange, transport of respiratory gases, pulmonary air volumes and lung capacities. Disorders of the respiratory system.

(v) Circulation: closed and open vascular systems, structure of human heart, cardiac cycle, systemic and pulmonary circulation, portal system, arterial blood pressure, origin and conduction of heart beat, blood vessels (structure with the help of diagrams and adaptation), lymphatic system. ABO groups, coagulation of blood. Disorders of the Circulatory system.

(vi) Excretion: ammonotelism, ureotelism, uricotelism, structure of human kidney (L.S.), structure of nephron, role of skin and lungs in excretion, physiology of urine formation, counter current system; functions of the kidney; homeostasis. Disorders of the excretory system.

(vii) Endocrine System (human): hormones of pituitary, pineal, thyroid, parathyroid, pancreas, adrenal glands and gonads; mechanism of hormone action; effect of hyposecretion and hypersecretion, feedback mechanism.

(viii) Nervous System (human): Central, autonomic and peripheral, structure of brain and spinal cord, reflex action, transmission of nerve impulse, saltatory conduction; sense organs (eye and ear). Receptors (mechanoreceptor, chemoreceptor, photoreceptor and thermoreceptors).

(ix) Locomotion: joints, structure of skeletal muscle, sliding filament theory of muscle contraction, red and white muscles, summation, tetanus and rigor mortis. Disorders of muscular and skeletal system.



  1. Units of Life

(i) Biomolecules: Outline classification and functions of Carbohydrates, proteins, lipids and nucleic acids.

(ii) Enzymes: General properties, classification, mechanism of enzyme action, factors affecting enzyme activity.

(iii) Cell membranes: fluid mosaic model, membrane transport, passive and active transport, exocytosis and endocytosis. Facilitated diffusion.

(iv) Cell structure: structure and functions of nucleus, mitochondria, plastids, endoplasmic reticulum, golgi complex, lysosomes, ribosomes, microfilaments, microtubules, cilia, flagella and centrioles (ultra structure and function); Cell wall, vacuoles and cell inclusions. Prokaryotic cell and eukaryotic cell – a comparison.

(v) Cellular respiration: aerobic and anaerobic, fermentation, glycolysis, Krebs’ cycle, oxidative phosphorylation and respiratory quotient. Amphibolic pathway.

(vi) Cell reproduction: cell cycle, mitosis and meiosis.


  1. Organisms and Environment

(i) Ecosystem: biotic and abiotic components, Productivity and decomposition, food chain, trophic levels, food webs, ecological pyramids, niche, biogeochemical cycles.


(ii) Pollution: Air, water and soil pollution and their control. Greenhouse effect and ozone depletion.