Class 10 Science Notes

CBSE groups the thirteen chapters into five units and marks them by unit, not by chapter, so the weight of a chapter depends on the unit it sits in. Knowing the split tells you where the marks are before you open a single textbook.

• Unit I — Chemical Substances: Nature and Behaviour, 25 marks: Chemical Reactions and Equations, Acids Bases and Salts, Metals and Non-Metals, Carbon and its Compounds.
• Unit II — World of Living, 25 marks: Life Processes, Control and Coordination, How do Organisms Reproduce, Heredity.
• Unit III — Natural Phenomena, 12 marks: Light, Reflection and Refraction, and The Human Eye and the Colourful World.
• Unit IV — Effects of Current, 13 marks: Electricity, and Magnetic Effects of Electric Current.
• Unit V — Natural Resources, 5 marks: Our Environment, the only assessed chapter in this unit.

The chemistry unit is the largest block of the paper at 25 marks, and it is the most learnable, because it rewards the definitions and the reactions rather than the derivations.

• Chemical Reactions and Equations — balancing, the types of reaction, and the oxidation-reduction and exothermic-endothermic ideas that appear in almost every paper.
• Acids, Bases and Salts — the properties, the pH scale, neutralisation, and the preparation and uses of Sodium Hydroxide, Bleaching powder, Baking soda, Washing soda and Plaster of Paris.
• Metals and Non-Metals — the properties of the two, the reactivity series, ionic compounds, the metallurgical processes, and corrosion with its prevention.
• Carbon and its Compounds — covalent bonding, the homologous series, the functional groups, the reactions of carbon compounds, ethanol and ethanoic acid, and soaps and detergents.

Biology is the other 25-mark unit, and it divides cleanly into the processes that keep an organism alive and the processes that pass life on. The first two chapters are the processes, the last two are reproduction and heredity.

• Life Processes — nutrition, respiration, transport and excretion, studied in both plants and animals, with the differences between the two drawn out clearly.
• Control and Coordination — tropic movements and plant hormones in plants, the nervous system and reflex action in animals, and chemical coordination by hormones.
• How do Organisms Reproduce — asexual and sexual reproduction in plants and animals, and reproductive health including family planning, safe sex and HIV/AIDS.
• Heredity — Mendel's experiments and his two laws, the monohybrid and dihybrid crosses, and sex determination.

The remaining 30 marks sit in the two physics units and the environment chapter, and these are the units where the formulas decide the marks, so the numericals carry the weight.

• Light, Reflection and Refraction — the mirror and lens formulae, magnification, the power of a lens, and the prism with dispersion and scattering.
• The Human Eye and the Colourful World — how the eye works as a lens, the defects of vision and their corrections, and the applications of mirrors and lenses.
• Electricity — Ohm's law, resistance and resistivity, the series and parallel combinations, the heating effect, and electric power.
• Magnetic Effects of Electric Current — the magnetic field of a conductor, coil and solenoid, the force on a conductor, Fleming's Left Hand Rule, and AC against DC with domestic circuits.
• Our Environment — the ecosystem, the environmental problems, ozone depletion, waste and its solutions, and the biodegradable and non-biodegradable distinction.

Five of the twenty internal marks come from the practical file, and the work is specified in the syllabus rather than left to the teacher, so the listed experiments are the ones to have recorded. Every practical listed in the syllabus must be completed.

• Unit I — finding the pH of six samples with pH paper, studying the properties of acids and bases, classifying four reactions by type, and arranging four metals by their action on salt solutions.
• Unit II — preparing a temporary mount of a leaf peel to show the stomata.
• Unit IV — plotting potential difference against current to find a resistance, and determining the equivalent resistance of two resistors in series and parallel.