Khan Academy Exercises and Videos

The Sensation of Touch

2026-06-12T11:00:48.455207

This video explores how the sense of touch works through the skin, our body’s largest and outermost sense organ.

Diseases of the Eye

2026-06-12T11:00:48.455207

Have you ever noticed that two people in the same room can see very differently, especially in dim light? This video explores why all eyes don’t see the same way by explaining common eye defects and diseases and what actually goes wrong inside the eye in each case.

Developmental Stages in Taste

2026-06-12T11:00:48.455207

Why does a sour lemon make a baby’s face scrunch up, while the same taste feels mild to adults or elderly people? This video explores how our sense of taste develops and changes throughout life, from infancy to old age.

Locomotion in Snake

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In this video, we explore the fascinating science behind how snakes move without legs.

Eye Protection

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Have you ever noticed how your eyes blink and water instantly when dust flies towards them—before you even realise what’s happening? This video explores how the human eye protects itself automatically and efficiently.

Functioning of ear

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In this video, we explore how your ear helps you hear and stay balanced every single day.

Taking care of the skin and diseases of the skin

2026-06-12T11:00:48.455207

Your skin does much more than cover your body—it protects you from germs, regulates temperature, and helps you sense the world around you. This video explains why skin care is an essential part of health, not just cleanliness or appearance.

Muscles and How do they work?

2026-06-12T11:00:48.455207

Every time you run, smile, blink, or catch yourself from falling, a quiet teamwork unfolds inside your body. This video explores how muscles make movement possible, even before you consciously think about it.

Diseases of the ear

2026-06-12T11:00:48.455207

This video explores how the ear works and what happens when it develops diseases or infections that interfere with hearing.

Preparation of hydrogen

2026-06-12T10:50:34.118117

This video explains the preparation of hydrogen gas in both laboratory and industrial settings. It covers the chemical principles behind hydrogen production, demonstrates the laboratory setup using zinc and dilute acids, explains why zinc reacts with acids through the activity series, and introduces alternative and commercial methods such as steam reforming and reactions involving hydrocarbons and steam. The lesson also compares different commercial hydrogen production techniques and discusses the chemistry involved in each method.

Density and Molar Mass of a Gaseous Substance (Worked problem)

2026-06-12T10:50:34.118117

This video explains how the ideal gas equation can be used to relate the density and molar mass of a gaseous substance. It shows the derivation of the formula connecting pressure, molar mass, temperature, and density, and then applies it step by step to worked examples. Learners will also review the importance of using correct units and gas constants when solving gas-law problems.

Unique position of hydrogen

2026-06-12T10:50:34.118117

This video explains the unique position of hydrogen in the periodic table. It compares hydrogen with both alkali metals (Group 1) and halogens (Group 17) to show why hydrogen cannot be placed perfectly in either group. The video covers hydrogen’s electronic configuration, electropositive and electronegative behavior, oxidation states, bonding characteristics, occurrence, and isotopes. This is suitable for school-level chemistry learners preparing for foundational inorganic chemistry topics.

Molecular Speeds of Gases

2026-06-12T10:50:34.118117

This video explains the Maxwell–Boltzmann distribution of molecular speeds and the three important characteristic speeds of gas molecules: 1. Most Probable Speed 2. Average Speed 3. Root Mean Square (RMS) Speed The lesson connects the microscopic motion of gas molecules with observable macroscopic gas behavior using the kinetic theory of gases. It also explains how temperature and molar mass affect molecular speed distributions and solves numerical problems based on the formulas.

Advance application and graph analysis

2026-06-12T10:50:34.118117

This lesson enables students to understand the applications of gas laws in different situations and to interpret the relationships between pressure, volume, temperature, and amount of gas. Through solved examples, real-life applications, and graphical analysis, students develop conceptual clarity and quantitative skills related to Boyle’s Law, Charles’ Law, Gay-Lussac’s Law, and Avogadro’s Law. The lesson also strengthens students’ ability to analyse graphs, compare trends, and interpret the physical significance of slope in gas law relationships.

Graham's Law (Worked problem)

2026-06-12T10:50:34.118117

This video introduces students to Graham’s law of diffusion/effusion and explains how the rate of diffusion/effusion of gases is related to their molar masses. The lesson begins with a short review of basic gas concepts, then presents the mathematical form of Graham’s Law and shows how to use it in solving simple problems. Students will also learn how the rate of diffusion/effusion can be expressed in terms of volume and time, and how lighter gases diffuse faster than heavier gases under the same conditions.

Addition polymerisation

2026-06-10T12:50:37.816026

Based on their mode of polymerisation, polymers can be either addition polymers or condensation polymers. In this video we deep dive into addition polymerisation and the various mechanism that lead to it – free radical polymerisation, cationic polymerisation and anionic polymerisation.

Condensation polymerisation and copolymerisation

2026-06-10T12:50:37.816026

Unlike addition polymerization which proceeds via chain growth, condensation polymerisation involves step growth. In this video we deep dive into these kind of polymerisation and look at various examples involving both homopolymers and copolymers along the way.

Rubber

2026-06-10T12:50:37.816026

In this video, we look at the various forms of rubber – natural, semi-synthetic and synthetic-how they are prepared, their various pros and cons and suitability for specific applications.

Classification of polymers

2026-06-10T12:50:37.816026

Polymers are macromolecules that are made of the same repeating unit. They are a major part of many of the materials we see around us and in this video we look into how we classify polymers – based on their source, their structure, mode of polymerization and intermolecular forces. We also look homopolymers and copolymers along the way.

Shapes of atomic orbitals - p and d orbital

2026-06-10T12:30:49.002061

This video explores the distinctive shapes and orientations of p and d orbitals, helping learners visualize how electrons occupy space around the nucleus. Step by step, it explains radial and angular nodes, showing how these features influence orbital structure. The lesson also covers the concept of degenerate orbitals, where multiple orbitals share the same energy.

Monthly car costs

2026-06-12T21:23:28.000000

Practice understanding of monthly costs of car ownership: from monthly car payments and regular expenses to factoring in occasional expenses like registration and oil changes.

Insurance contracts

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Practice understanding of insurance contracts including declarations, exclusions, endorsements, insuring agreement, and conditions

Understand: Birthright Citizenship

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Check your understanding of the birthright citizenship with this set of multiple-choice questions.

Structure of the Skin

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Learn the structure of the human skin - its layers (epidermis, dermis, and fat), glands, hair follicles, and pigment cells. Understand how these parts protect, regulate, and maintain the body’s temperature and texture.

Understand: The solar system

2026-06-12T08:16:47.000000

Check your understanding of the solar system in this set of free practice questions aligned to NGSS standards.

Functions of joints and cartilages

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LO: Functions of joints and cartilages

Plant fibers and their uses

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LO: Plant fibers and their uses. LO2: Cotton and Jute

Cells

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Let's do some questions

Formation of soil

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Let's solve some questions

Methods of separation

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LO: Understand the various separation methods like threshing, handpicking, evaporation, condensation, filtration, sedimentation, decantation, chromatography etc.

Types of changes

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LO1: Types of changes - Fast and slow changes - Physical and chemical changes - Natural and artificial changes/ Controlled and Uncontrolled changes - Reversible and irreversible changes/ Regular and irregular changes.

Micro-organisms (Fundamentals)

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Let's solve some problems to better understands some fundamental properties of micro-organisms.

Cell structures and their functions

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Test your knowledge of cell structures and their functions!

Methods of food protection

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Let's practice!

Prime factorization of larger numbers

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Let's practice prime factorizing three and four digit numbers like 1242.

Interpret graphs of functions

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Interpret the graphs of both linear and nonlinear functions.

Constant of proportionality from equations

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Practice identifying the constant of proportionality from equations.

Graph sinusoidal functions

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Given the formula of a sinusoidal function of the form a*f(bx)+d, draw its graph.

Period of sinusoidal functions from graph

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Given the graph of a sinusoidal function, determine its period.

Gravitational fields

2026-06-11T15:08:37.000000

Check your understanding of the gravitational field in this set of free practice questions.