Matter in Our Surroundings – Key Vocabulary

Vocabulary flashcards covering all major terms and definitions from the lecture on 'Matter in Our Surroundings' to aid exam preparation.

Matter

Anything that occupies space, has mass and volume; makes up all physical substances in the universe.

Panch Tatva

Ancient Indian classification of matter into five basic elements—air, earth, fire, sky and water.

Particle Theory of Matter

Concept that matter is composed of tiny, discrete particles with space between them.

Diffusion

Spontaneous intermixing of particles of two substances due to random motion, fastest in gases, slowest in solids.

Kinetic Energy (of particles)

Energy of motion possessed by particles; increases with temperature causing faster movement.

Physical States of Matter

The three common forms—solid, liquid and gas—differing in particle arrangement, movement and attraction.

Solid

State with definite shape and volume, negligible compressibility and strong intermolecular forces; particles vibrate about fixed positions.

Liquid

State with definite volume but no fixed shape; moderate compressibility, particles can slide past one another, making liquids fluid.

Gas

State with neither fixed shape nor volume, highly compressible with particles moving randomly at high speeds.

Compressibility

Ability of a substance to decrease in volume under pressure; highest in gases, negligible in solids.

Rigidity

Tendency of a solid to retain its shape when an external force is applied.

Fluidity

Ability of liquids and gases to flow and take the shape of their container.

Melting Point

Temperature at which a solid changes to a liquid at atmospheric pressure (0 °C or 273 K for ice).

Fusion

Process of melting; change from solid to liquid state.

Boiling Point

Temperature at which a liquid’s vapour pressure equals atmospheric pressure and it changes to gas (100 °C or 373 K for water).

Latent Heat of Fusion

Heat energy required to convert 1 kg of a solid into liquid at its melting point without temperature change.

Latent Heat of Vaporisation

Heat energy required to convert 1 kg of a liquid into vapour at its boiling point without temperature change.

Sublimation

Direct change of a substance from solid to gas without passing through the liquid state (e.g., camphor, naphthalene).

Deposition

Direct change of a substance from gas to solid without becoming liquid.

Evaporation

Surface phenomenon where particles of a liquid escape into vapour at temperatures below boiling point.

Factors Affecting Evaporation

Surface area ↑, temperature ↑, wind speed ↑ and humidity ↓ all speed up evaporation.

Density

Mass per unit volume of a substance; expressed in kg m⁻³ (density = mass/volume).

Atmospheric Pressure

Pressure exerted by the weight of air at sea level; standard value is 1 atm (1.01 × 10⁵ Pa).

Kelvin Scale

SI temperature scale starting at absolute zero; °C to K conversion: K = °C + 273.

Interconversion of States

Change among solid, liquid and gas by altering temperature or pressure.

Space Between Particles

Microscopic gaps separating particles; smallest in solids, greatest in gases.

Force of Attraction Between Particles

Intermolecular forces holding particles together; strongest in solids, weakest in gases.

Humidity

Amount of water vapour present in air; higher humidity slows evaporation.

Surface Phenomenon

Process (e.g., evaporation) occurring only at the surface of a liquid.

Bulk Phenomenon

Process (e.g., boiling) involving particles throughout the entire volume of the substance.

Dry Ice

Solid carbon dioxide that sublimates at atmospheric pressure, used for cooling.

CNG (Compressed Natural Gas)

Methane-rich fuel stored under high pressure for use in vehicles.

LPG (Liquefied Petroleum Gas)

Propane–butane mixture stored as a liquid under pressure for cooking and heating.

Temperature Effect on Kinetic Energy

Rising temperature increases particle kinetic energy, enhancing diffusion and state changes.

Pressure Effect on State

Increasing pressure (and lowering temperature) can liquefy gases by forcing particles closer.

Pascal (Pa)

SI unit of pressure equal to 1 N m⁻².

SI Unit of Mass

Kilogram (kg), standard measure of mass.

SI Unit of Volume

Cubic metre (m³); common laboratory unit is litre (L) where 1 L = 1000 mL.