IGCSE Grade 6 Chemistry: 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).

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.

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.

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

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.