Understanding Matter: States, Changes, and Mixtures

States of Matter and Their Changes

State changes are processes experienced by the body according to the environmental conditions of pressure and temperature.

• Solid-Liquid (Fusion)
• Liquid-Gas (Vaporization)
• Gas-Solid (Deposition)
• Liquid-Solid (Solidification)
• Solid-Gas (Sublimation)
• Gas-Liquid (Condensation)

When heating a body, the energy of the particles increases. There comes a moment when this energy is sufficient to overcome the forces of cohesion, and then fusion occurs when we consider that part of a solid body. The same applies to all states of aggregation. The form of fusion of a body depends on its nature. We will distinguish between crystalline and amorphous bodies.

• In a crystalline body, such as ice, melting is produced at a constant temperature called the fusion temperature, which may vary depending on the pressure. (Ice melts at 0 degrees Celsius at atmospheric pressure.)
• In an amorphous body, such as glass, fusion occurs within a wide temperature range, during which the body passes through a pasty state. (Glass melts at 1200 degrees Celsius.)

Separation of Mixtures

• Filtration: In this case, the liquid or dissolved substance may pass through the pores of the filter paper. The particle size will be smaller than the pores of the paper, but undissolved solids do not come through.
• Decantation: This separation is based on the components having different densities. Therefore, the less dense component is on top. Example: a heterogeneous mixture of water and sand.
• Magnetism: Based on the properties of some components, it is characterized by being attracted to a magnet. Example: a mixture formed by iron filings and sand.

Homogeneous Mixtures and Solutions

Solutions are homogeneous mixtures and are formed when a substance (usually a solid) dissolves in another (usually a liquid).

The solid is called the solute, and the liquid part is called the solvent.

A solution is always clear; if it is cloudy, it is called a suspension. In a suspension, the solute particles are larger than in a solution. If left standing, many of the solid particles in a suspension will precipitate.

Colloidal Substances

Colloids are mixtures that are insoluble in one another and are in the form of very small particles that remain suspended without sedimenting. Example: milk.

In a colloid, particles of one substance are dispersed in another. Dispersed particles are larger than those of a solution but smaller than those of a suspension.

Particles are dispersed throughout the mixture. The set is called the particulate phase. The phase in which particles are dispersed is called the continuous phase.

If a colloid is formed by two liquids, the substance is known as an emulsion.

An experimental test can tell if a mixture is a colloid or a solution if we pass a ray of light through the mixture.

If the light passes through the substance without scattering, it is a solution.