Elements, Compounds and Mixtures

• (a) Kerosene oil and water: Separating Funnel (Immiscible liquids forming two separate layers based on density).
• (b) Ammonium chloride and common salt: Sublimation (Ammonium chloride sublimes on heating, leaving salt behind).
• (c) Pigments in flower extract: Paper Chromatography (Separates soluble organic pigments by differential capillary adsorption).
• (d) Ethanol and water: Fractional Distillation (Miscible liquids having boiling points close to each other: ethanol $78^{\circ}\text{C}$, water $100^{\circ}\text{C}$).
• (e) Iron filings and sulphur powder: Magnetic Separation (A magnet attracts magnetic iron filings away from non-magnetic sulphur).

• Metalloid (Semimetal): An element that displays physical and chemical properties intermediate between those of typical metals and non-metals.
• Three Examples:
1. Silicon (Si)
2. Germanium (Ge)
3. Arsenic (As) (also Antimony [Sb], Tellurium [Te]).
• Significance in Electronics: Metalloids are semiconductors: their electrical conductivity increases with temperature and can be precisely modulated by adding trace impurities ("doping"). They are the indispensable core materials used to manufacture microchips, computer processors, transistors, and solar cells.

• Step 1: Sublimation:
Place the mixture in a china dish covered with an inverted glass funnel whose neck is plugged with cotton. Heat gently. Ammonium chloride sublimes, and its vapors condense on the cool inner walls of the funnel as a white sublimate. Scrape it off. The dish now contains only Sand and Salt.
• Step 2: Dissolution in Water:
Add water to the remaining mixture and stir thoroughly. Salt dissolves completely in water, while sand remains insoluble.
• Step 3: Filtration:
Filter the suspension. Sand is retained on the filter paper as the residue, while the clear salt solution passes through as the filtrate.
• Step 4: Evaporation:
Heat the filtrate to evaporate all water, leaving pure dry Common Salt crystals behind.

• Principle of Paper Chromatography:
It is based on the differential solubility and partition of different solute components between two phases: a stationary phase (water absorbed on cellulose filter paper fibers) and a mobile phase (the moving solvent).
As the solvent travels upward through the paper by capillary action, components that are more soluble in the solvent and less adsorbed by the paper travel faster and farther, separating into distinct colored bands.
• Retention Factor ($R_f$):
A characteristic ratio defined as:

$$\mathbf{R_f = \frac{\text{Distance traveled by the solute component}}{\text{Distance traveled by the solvent front}}}$$

$R_f$ is a constant identifier for a specific substance under given experimental conditions.

• Simple Distillation is effective only when the boiling points of two miscible liquids differ by a large margin (typically more than $25^{\circ}\text{C}$ to $30^{\circ}\text{C}$).
• The boiling point of ethanol is $78^{\circ}\text{C}$ and water is $100^{\circ}\text{C}$ (a small difference of only $22^{\circ}\text{C}$).
• When the mixture boils, substantial water vapor escapes along with ethanol vapor.
• A Fractionating Column contains glass beads that provide a large surface area for repeated vaporization and condensation cycles. The higher-boiling water vapor condenses and trickles back down, while pure low-boiling ethanol vapor reaches the top and enters the condenser.

1. Luster: Metals have metallic shine (lustrous); Non-metals are dull (except iodine and graphite).
   2. Malleability & Ductility: Metals are malleable and ductile; Non-metals are brittle and break easily under stress.
   3. Electrical Conductivity: Metals are good conductors due to free electrons; Non-metals are insulators (except graphite).
   4. Sonority: Metals produce a deep ringing sound when struck (sonorous); Non-metals are non-sonorous.

• Difference: An Alloy is a homogeneous physical mixture of two or more metals (or a metal and a non-metal). Its constituents retain their chemical identities and are not bonded in a fixed atomic ratio.
• A Compound is formed by chemical bonding in a strict, unvarying ratio by mass with completely new chemical properties.
• Examples of Alloys:
1. Brass: Copper ($60-80\%$) $+$ Zinc ($20-40\%$).
2. Bronze: Copper ($88\%$) $+$ Tin ($12\%$).
3. Steel: Iron ($99\%$) $+$ Carbon ($1\%$).

1. Thermal Decomposition: Some solid chemical compounds (like sugar or copper sulphate) decompose or get charred when heated to dryness during evaporation.
   2. Soluble Impurities: In simple evaporation, all dissolved soluble impurities remain behind mixed with the solid residue. In crystallisation, only the pure substance forms orderly crystal lattices, leaving all soluble impurities dissolved in the "mother liquor".