IGCSE Grade 6 Chemistry: States of Matter

States of Matter

• Matter exists in three states: solids, liquids, and gases.
• Matter comprises tiny particles known as atoms, the smallest unit of a substance (element).

Particle Theory of Matter

• All matter is made up of particles that are constantly in motion.
• The motion and arrangement of these particles determine the properties of each state of matter.

Changing States of Matter

• Melting:

  • A cold substance absorbs energy when heated, overcoming attractive forces between particles.
  • Increased temperature leads to solids melting; for example, ice melts at temperatures above 0°C.

• Freezing:

  • The process involves heat transfer from a hot substance to its surroundings.
  • The decrease in temperature leads to close packing of particles, resulting in a solid form; water freezes into ice at 0°C.

• Vaporization:

  • Occurs when water boils, with bubbles forming as molecules gain enough energy to transition to gas.
  • Water vaporizes at a boiling point of 100°C, changing from liquid to gaseous state.

• Condensation:

  • Involves vapor losing energy when in contact with cold surfaces, leading to a transition from gas to liquid.
  • This process is the reverse of vaporization, forming droplets of liquid water.

• Sublimation:

  • Direct transition from solid to gas occurs when solids absorb energy sufficient to overcome intermolecular forces.
  • A common example is dry ice transitioning directly to carbon dioxide gas.

• Deposition:

  • The reverse of sublimation; gas transitions directly to solid without passing through a liquid state.

Breathing in Space

• Space is a vacuum, lacking particles.
• Astronauts rely on oxygen supplies in backpacks, which circulate through spacesuits for breathing.

Tests for Gases

• Unique tests identify gases in compounds, ensuring clear results.

• Oxygen:

  • Glowing splint relights when introduced to oxygen in a test tube, indicating its presence.

• Hydrogen:

  • A lighted splint produces a squeaky pop when near hydrogen, confirming its presence.

• Carbon Dioxide:

  • Bubbling carbon dioxide through limewater (calcium hydroxide solution) forms a white precipitate of calcium carbonate, turning the solution milky, indicating the presence of carbon dioxide.

Summary Table of Gas Tests

• Oxygen: Glowing splint relights → Oxygen is present.
• Hydrogen: Lighted splint pops → Hydrogen is present.
• Carbon Dioxide: Limewater turns milky → Carbon dioxide is present.