iGCSE Chemistry (Combined) CAIE

This subject is broken down into 32 topics in 12 modules:

  1. The Particulate Nature of Matter 1 topics
  2. Experimental Techniques 3 topics
  3. Atoms, Elements and Compounds 5 topics
  4. Stoichiometry 1 topics
  5. Electricity and Chemistry 1 topics
  6. Energy Changes in Chemical Reactions 1 topics
  7. Chemical Reactions 2 topics
  8. Acids, Bases and Salts 3 topics
  9. The Periodic Table 5 topics
  10. Metals 3 topics
  11. Air and Water 3 topics
  12. Organic Chemistry 4 topics
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  • 12
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  • 32
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  • 11,651
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  • 1+
    hours of audio lessons

This page was last modified on 28 September 2024.

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Chemistry (Combined)

The Particulate Nature of Matter

The Particulate Nature of Matter

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The Particulate Nature of Matter

The Particulate Nature of Matter

Basic Principles

  • All substances are made of particles.
  • These particles could be atoms, molecules, or ions.
  • These particles are in constant motion; higher the temperature, quicker the movement.
  • There are spaces between particles.

States of Matter

  • Matter exists in three states: Solid, Liquid, and Gas.
  • In solids, particles are packed closely in a fixed pattern. They can only vibrate around a fixed point.
  • In liquids, particles are close but can move around each other. This means liquids can flow and take shape of their containers.
  • In gases, particles are well separated and move quickly in all directions. Gases fill their containers completely.

Changes of States

  • Melting and Freezing: The change from solid to liquid is called melting, whereas the change from liquid to solid is freezing.
  • Boiling and Condensing: Liquid turning into gas is boiling or evaporation, while gas changing to liquid is called condensing.
  • Sublimation: Certain substances can change from solid directly to gas, bypassing the liquid state. This process is called sublimation.

Kinetic Particle Theory

  • The Kinetic Particle Theory explains the properties of different states of matter.
  • This theory considers both the movement of particles (kinetic energy) and the attraction between them.
  • In solids, the attractive forces are strong, keeping particles in fixed positions, so solids keep their shape.
  • In liquids, the attractive forces are weaker, allowing particles to move and slide past each other.
  • In gases, the attractive forces are very weak, letting particles move rapidly in all directions.

Diffusion

  • Diffusion is the spreading of particles from an area of high concentration to one of low concentration.
  • Diffusion occurs most quickly in gases, slower in liquids, and slowest in solids.
  • Increased temperature boosts the speed of diffusion by increasing particle motion.

Brownian Motion

  • Brownian Motion is the random, unpredictable movement of particles in a fluid, as observed under a microscope.
  • This motion is caused by the collisions of the particles with each other.
  • Brownian Motion is additional evidence of the particle nature of matter.

Course material for Chemistry (Combined), module The Particulate Nature of Matter, topic The Particulate Nature of Matter

Chemistry (Combined)

Acids, Bases and Salts

Identification of Ions and Gases

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Identification of Ions and Gases

Identification of Positive Ions (Cations)

  • Copper (II), Cu^2+, can be identified by a blue precipitate formed after reacting aqueously with sodium hydroxide.
  • Iron (II), Fe^2+, produces a green precipitate with sodium hydroxide, which then turns brown.
  • Iron (III), Fe^3+, when reacted with sodium hydroxide, forms a reddish-brown precipitate.
  • Calcium, Ca^2+, forms a white precipitate with sodium hydroxide, insoluble in excess.
  • Aluminium, Al^3+, reacts with sodium hydroxide to produce a white precipitate, dissolved in excess.
  • Ammonium, NH4+, is tested by warming with sodium hydroxide, which gives off ammonia gas that turns damp red litmus paper blue.

Identification of Negative Ions (Anions)

  • Chloride, Cl^–, when treated with dilute nitric acid and silver nitrate, forms a white precipitate.
  • Bromides, Br^– and Iodides, I^–, when reacted with dilute nitric acid and silver nitrate form a cream or yellow precipitate respectively.
  • Sulphates, SO4^2–, when reacted with dilute hydrochloric acid and barium chloride, form a white precipitate.
  • Carbonates, CO3^2–, on reacting with any dilute acid, produce carbon dioxide, detected by bubbling through lime water (turning from clear to milky).

Identification of Gases

  • Hydrogen gas is recognised by a 'pop' sound when a lit splint is introduced in its test tube.
  • Oxygen gas relights a glowing splint.
  • Carbon dioxide, when bubbled through clear lime water, turns it milky.
  • Ammonia gas is alkaline and has a pungent odour. It turns damp red litmus paper blue.
  • Chlorine gas has a sharp, bad smell and bleaches damp litmus paper.

Course material for Chemistry (Combined), module Acids, Bases and Salts, topic Identification of Ions and Gases

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