Matter Properties, Changes, and Separation Methods
Chemistry: Matter and Its Properties
Chemistry is the science of matter, its properties, and the changes it undergoes. Matter is all around us; it has mass and occupies a volume, even if it is sometimes invisible.
Homogeneous and Heterogeneous Mixtures
- A homogeneous mixture, or solution, has the same composition at every point (e.g., sugar dissolved in water).
- A heterogeneous mixture does *not* have the same composition at every point, and its components are distinguishable.
States of Matter and Their Changes
States of Matter
- Solids: Fixed volume and shape; cannot be compressed; do not flow.
- Liquids: Fixed volume, but take the shape of their container; very difficult to compress; flow.
- Gases: No fixed shape or volume; easily compressed; flow easily, tending towards maximum disorder.
Changes that modify the nature and composition of matter are called chemical changes.
Changes of State
- Solid to Liquid: Fusion
- Liquid to Solid: Solidification
- Fusion Temperature (Tf): The temperature at which a substance changes from solid to liquid.
- Liquid to Gas: Vaporization
- Gas to Liquid: Liquefaction
- Boiling Point (Teb): The temperature at which a liquid boils and becomes gaseous.
- Solid to Gas: Sublimation
- Gas to Solid: Deposition (also called reverse sublimation)
Separation Methods for Mixtures
Heterogeneous Mixtures
The following methods can be used for heterogeneous mixtures:
- Settling: Used when components have different densities (e.g., oil and water). The mixture is left to stand until the denser component settles at the bottom.
- Filtration: Used for solid-liquid mixtures where settling is not effective. The mixture is poured through a filter that allows the liquid to pass but retains the solid.
- Manual Separation: Used when the mixture consists of solid particles of appreciable size (e.g., stones and vegetables).
- Screening: The mixture is passed through a sieve.
- Magnetization: Used when one component has magnetic properties (e.g., separating metals from sand).
Homogeneous Mixtures
The following methods can be used for homogeneous mixtures:
- Distillation: Used for mixtures of liquids with significantly different boiling points. The mixture is heated until the more volatile component reaches its boiling point, vaporizes, and is then condensed back into a liquid by cooling.
- Crystallization: Used for homogeneous solid-liquid mixtures (solutions, e.g., salt and water). The mixture is heated to evaporate the liquid component until crystallites of the solid component begin to form.
Material Properties
Materials are useful because of their properties. Some of the most important are:
- Elasticity: The ability of a material to regain its original shape after the deforming force is removed (e.g., a rubber band).
- Fragility: The ease with which a material cracks or breaks upon impact (e.g., crystals and glass).
- Ductility: The ability of a material to be stretched into threads (e.g., copper and aluminum).
- Tenacity: The resistance of a material to breaking when a force is applied (e.g., metals).
- Hardness: The resistance of a material to being scratched by another material (e.g., diamonds).
- Malleability: The capacity of a material to be spread into sheets (e.g., tin).
- Plasticity: The ability of a material to maintain its new shape after being deformed (e.g., plasticine).