The Nature and Separation of Matter
This briefing document summarises the fundamental concepts of matter, its properties, changes, and various methods for separating mixtures, drawing from "Matter.pdf" and "Separation-Methods.pdf".
1. Defining Matter and Chemistry
Chemistry is presented as "the science of the composition, structure, properties and reactions of matter," or alternatively, "the science dealing with the composition of matter and changes it undergoes." (Matter.pdf)
Matter is fundamentally defined as "anything that occupies space and has mass." (Matter.pdf)
The study of chemistry involves understanding the "composition, structure, and properties of matter; quantitative principles, kinetics, and energetics of transformations of matter; and fundamental concepts of organic chemistry." (Matter.pdf)
2. Classification of Matter
Matter is broadly categorised into pure substances and mixtures.
2.1 Pure Substances
A "pure homogeneous material that is made up of only one kind of matter" and has a "definite, fixed composition." (Matter.pdf)
Elements: "a pure substance that cannot be decomposed or transformed into other elements by chemical means. It is represented by a symbol." (Matter.pdf)
Metals: e.g., Fe, Au, Al
Non-metals: e.g., C, H, O, N, Cl
Metalloids: e.g., B, Si, As
Compounds: "substances of two or more elements that are chemically combined in definite proportions." (Matter.pdf)
Can be decomposed by simple chemical changes like electrolysis and pyrolysis.
Classification of Compounds:
Organic: "compounds that contain carbon."
Inorganic: "compounds that do not contain carbon."
Acid: "gives H+ in a solution... compound that turns blue litmus paper to red and has a sour taste."
Base: "gives OH- in a solution... compounds that turns red litmus paper to blue and has a bitter taste."
Salt: "compound that has no reaction to litmus paper and has a salty taste."
Covalent: "compound whose constituents elements are bonded by sharing electrons."
Ionic or Electrovalent: "compound whose constituents elements are bonded by transfer electrons."
Electrolyte: "compound whose aqueous solution or molten state conducts electricity."
Non-electrolyte: "compound whose solution does not conduct electricity." (Matter.pdf)
2.2 Mixtures
A "combination of two or more elements and/or compounds that retain their chemical identities." (Matter.pdf) In a mixture, components "do not chemically combine" and "retain their original properties," meaning they "can be separated by physical means." (Separation-Methods.pdf)
Homogeneous: Components are "evenly distributed throughout thus the components can not be distinguished from one another."
Heterogeneous: Components are "not evenly distributed thus the components can be distinguished from one another." (Matter.pdf)
3. States of Matter
The four states of matter are Solid, Liquid, Gas, and Plasma. (Matter.pdf) These states are differentiated based on "particle arrangement," "energy of particles," and "distance between particles," following the Kinetic Theory of Matter, which states that "Matter is made up of particles which are in continual random motion." (Matter.pdf)
Solids: Particles are "tightly packed, vibrating about a fixed position." They have a "definite shape and a definite volume."
Liquids: Particles are "tightly packed, but are far enough apart to slide over one another." They have an "indefinite shape and a definite volume."
Gases: Particles are "very far apart and move freely." They have an "indefinite shape and an indefinite volume."
Plasma: "a gas that is composed of free-floating ions (atoms stripped of some electrons - positively charged) and free electrons (negatively charged)." Plasma "conducts electrical currents" and was discovered by William Crookes in 1879. Examples include plasma in stars and the solar wind. (Matter.pdf)
4. Properties and Changes of Matter
4.1 Properties of Matter
"Each substance has a set of properties that are characteristic of that substance and give it a unique identity." These are classified as physical or chemical properties. (Matter.pdf)
Physical Properties: "inherent characteristics of substance that can be determined without altering its composition; they are associated with its physical existence." They can be "perceived by the senses and is expressed in definite numbers."
Extensive or Extrinsic: Depend on the amount of material (e.g., size, shape, length, weight, temperature).
Intensive or Intrinsic: Depend on the kind of material (e.g., melting point, boiling point, density, specific heat, hardness).
Chemical Properties: Describe "the ability of a substance to form a new substances, either by reaction with other substances or by decomposition." Examples include iron rusting, wood decaying, and alcohol burning. (Matter.pdf)
4.2 Changes of Matter
Physical Change: "a change in the physical properties or changes in the state of matter without accompanying change in composition." These changes "does not result in the formation of a new substance." Macroscopically, "The matter is the same. The original matter can be recovered." Microscopically, "The particle of the substance are rearranged." (Matter.pdf)
Chemical Change (Chemical Reaction): "a result in the formation of a new substance with new properties." "New substances are formed that have different properties and composition from the original material." Macroscopically, "The matter is different. The old matter is no longer present. The original matter cannot be recovered." Microscopically, "The particles of the substance are broken apart, and the atoms are rearranged into new particles, forming a new substance." (Matter.pdf)
5. Methods for Separating Mixtures
Since components in a mixture are physically combined, separation techniques are "based on differences in physical properties." (Separation-Methods.pdf)
Filtration: Separates a solid from a fluid by passing the mixture through a porous material. "Works by letting the fluid pass through but not the solid." (e.g., coffee filter separating coffee flavour from beans).
Magnetism: Used if "one component of the mixture has magnetic properties" (e.g., separating nails from wood chips).
Hand Separation: Manually separating parts of a mixture, only useful when "particles are large enough to be seen clearly" (e.g., separating ingredients in a salad).
Decantation: Separates an insoluble solid from a liquid by allowing the solid to settle and then carefully pouring off the liquid. Also applicable for separating two immiscible liquids.
Sifting or Sieving: Separates dry mixtures with substances of different sizes by passing them through a sieve (e.g., separating sand from pebbles).
Evaporation: Allows a liquid to evaporate, leaving a soluble solid behind (e.g., heating sugar water to leave sugar crystals).
Chromatography: Used to "separate dissolved substances in a solution from each other," based on differential movement through a stationary and mobile phase (e.g., separating ink components).
Crystallization: A separation technique resulting in "the formation of pure solid particles from a solution containing the dissolved substance," often by evaporation of one substance, leading to the dissolved substance collecting as crystals. "Produces highly pure solids."
Centrifuging: Rotates containers of liquids at high speed to "separate suspended materials with different densities" or to clarify solutions (e.g., separating fat from milk, or the spin drier in washing machines).
Distillation: Used to separate "homogeneous mixtures" based on "differences in boiling points of substances involved." (Separation-Methods.pdf)