CBSE Class 10 Science Rapid Revision Guide: Laws, Formulas, and Rules

When entering the final sprint before the CBSE Class 10 Science board examination, studying hundreds of pages of textbook chapters is inefficient. What you need is a consolidated, cross-disciplinary Rapid Revision Guide that brings together every fundamental scientific law, balanced chemical equation, physiological pathway, ray-tracing convention, and electrical formula across Physics, Chemistry, and Biology.

This master revision sheet is organized by discipline to serve as your ultimate exam-morning companion.

Part 1: Chemistry (Chapters 1 to 4)

1. Types of Chemical Reactions (Chapter 1)

• Combination: $CaO + H_2O \longrightarrow Ca(OH)_2 + \text{Heat}$ (Slaking of lime; vigorous exothermic reaction).
• Decomposition:
  • Thermal: $2FeSO_4 \xrightarrow{\Delta} Fe_2O_3 + SO_2 + SO_3$ (Green crystals $\to$ brown residue).
  • Thermal: $2Pb(NO_3)_2 \xrightarrow{\Delta} 2PbO + 4NO_2 \uparrow + O_2$ (Brown fumes of $NO_2$).
  • Photolytic: $2AgCl \xrightarrow{\text{Sunlight}} 2Ag + Cl_2$ (White to grey; black & white photography).
  • Electrolytic: $2H_2O \xrightarrow{\text{Electricity}} 2H_2 + O_2$ (Volume ratio of $H_2 : O_2 = 2 : 1$).
• Displacement: $Fe + CuSO_4 \longrightarrow FeSO_4 + Cu$ (Blue solution turns light green).
• Double Displacement (Precipitation): $Na_2SO_4 + BaCl_2 \longrightarrow BaSO_4 \downarrow + 2NaCl$ (White precipitate of $BaSO_4$).

2. Acids, Bases, and Salts (Chapter 2)

• Chlor-Alkali Process: $2NaCl + 2H_2O \xrightarrow{\text{Electrolysis}} 2NaOH + Cl_2\text{ (anode)} + H_2\text{ (cathode)}$
• Bleaching Powder: $Ca(OH)_2 + Cl_2 \longrightarrow CaOCl_2 + H_2O$
• Baking Soda: $NaCl + H_2O + CO_2 + NH_3 \longrightarrow NH_4Cl + NaHCO_3$
• Washing Soda: $Na_2CO_3 + 10H_2O \longrightarrow Na_2CO_3 \cdot 10H_2O$
• Plaster of Paris (POP): $CaSO_4 \cdot 2H_2O \xrightarrow{373\text{ K}} CaSO_4 \cdot \frac{1}{2}H_2O + 1\frac{1}{2}H_2O$

3. Metals and Carbon Compounds (Chapters 3 & 4)

• Thermite Reaction: $Fe_2O_3 + 2Al \longrightarrow 2Fe + Al_2O_3 + \text{Heat}$ (Welding railway tracks).
• Esterification: $CH_3COOH + C_2H_5OH \xrightarrow{\text{Acid}} CH_3COOC_2H_5\text{ (Sweet-smelling ester)} + H_2O$
• Saponification: $\text{Ester} + NaOH \longrightarrow \text{Soap } (CH_3COONa) + \text{Ethanol}$
• Cleansing Action of Soap: Hydrocarbon tail is hydrophobic (binds dirt); ionic head is hydrophilic (binds water), forming spherical micelles.

Part 2: Biology (Chapters 5 to 8 & 13)

1. Life Processes (Chapter 5)

• Photosynthesis Equation: $6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O$
• Breakdown of Glucose by Various Pathways:
  • Aerobic (Mitochondria): $\text{Pyruvate} + O_2 \longrightarrow 6CO_2 + 6H_2O + 38\text{ ATP}$
  • Anaerobic in Yeast (Fermentation): $\text{Pyruvate} \longrightarrow \text{Ethanol} + CO_2 + 2\text{ ATP}$
  • Anaerobic in Muscle (Cramps): $\text{Pyruvate} \longrightarrow \text{Lactic Acid} + 2\text{ ATP}$
• Double Circulation in Humans: Blood passes through the heart twice in one complete cycle (Pulmonary and Systemic circulation). Prevents mixing of oxygenated and deoxygenated blood.

2. Genetics and Environment (Chapters 8 & 13)

• Mendel's Monohybrid Ratio: Phenotypic $= \mathbf{3 : 1}$; Genotypic $= \mathbf{1 : 2 : 1}$
• Mendel's Dihybrid Ratio: Phenotypic $= \mathbf{9 : 3 : 3 : 1}$
• Sex Determination in Humans: Father determines the sex of the child (passes $X$ to female, $Y$ to male).
• 10% Law of Energy: Only $10\%$ of energy transfers to the next trophic level; $90\%$ lost as metabolic heat.
• Biomagnification: Maximum toxic pesticide concentration occurs at the top trophic level (Humans).
• Ozone Formation: $O_2 \xrightarrow{UV} O + O$, then $O + O_2 \longrightarrow O_3$.

Part 3: Physics (Chapters 9 to 12)

1. Optics: Mirrors and Lenses (Chapters 9 & 10)

• Snell's Law: $\frac{\sin i}{\sin r} = n_{21} = \frac{v_1}{v_2}$
• Absolute Refractive Index: $n = \frac{c}{v} = \frac{3 \times 10^8\text{ m/s}}{v}$

2. Electricity & Magnetism (Chapters 11 & 12)

• Ohm's Law: $V = I R$
• Resistance Formula: $R = \rho \frac{l}{A}$ (Resistivity $\rho$ depends ONLY on material and temperature).
• Resistors in Series: $R_s = R_1 + R_2 + R_3$ (Current $I$ is same; voltage divides).
• Resistors in Parallel: $\frac{1}{R_p} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}$ (Voltage $V$ is same; current divides).
• Joule's Law of Heating: $H = I^2 R t = V I t = \frac{V^2}{R} t$
• Electric Power: $P = V I = I^2 R = \frac{V^2}{R}$
• Commercial Energy: $1\text{ kWh} = \mathbf{3.6 \times 10^6\text{ Joules}}$

Hand Rules Memory Summary:

• Right-Hand Thumb Rule: Points along wire; thumb $=$ current, curled fingers $=$ magnetic field circles.
• Fleming's Left-Hand Rule (Electric Motors): F-M-C $\implies$ Thumb $=$ Force, Forefinger $=$ Magnetic Field, Middle $=$ Current.
• Fleming's Right-Hand Rule (Electric Generators / EMI): Thumb $=$ Motion, Forefinger $=$ Field, Middle $=$ Induced Current.

Important: <u>Mastering these foundational laws and formulas across Physics, Chemistry, and Biology equips you with the complete toolkit required to score 95%+ in your CBSE Class 10 Science board exam!</u>