10th Class: Occurrence and Extraction of Metals

Unit 10: Occurrence of Metals

• Some metals, like gold and platinum, are found in nature as free elements in their ores.
• Other metals occur as compounds (oxides, sulfides, carbonates).

Unit 10: Extraction of Metals

• Separating metals from their ores is a key step.
• Some metals (e.g., gold) can be separated by physical methods like panning.
• Unreactive metals are often extracted by heating their metal ores.
• Silver, mercury, and platinum are examples.
• Reaction with heat removes oxygen from metal oxide. This is called reduction.
• Carbon is a common reducing agent.

Unit 11: Metal + Oxygen → Metal Oxide

• Metals react with oxygen to form metal oxides.
• Different metals exhibit various reactions with oxygen, each characterised by a specific flame colour and product.
• Potassium burns vigorously with a lilac flame to form a white powder.
• Sodium reacts vigorously with a golden yellow flame producing a white powder.
• Calcium burns vigorously with a brick-red flame to form a white powder.
• Magnesium burns with a very bright white flame to form a white powder.
• Zinc forms a pale yellow powder when hot and white when cold.
• Copper forms a black product.

Unit 11: Metal + Water → Metal Hydroxide + Hydrogen

• Highly reactive metals can react with cold water, producing hydrogen gas.

• Potassium, sodium, and calcium form metal hydroxides when reacting with water.

• These reactions are vigorous and give off hydrogen gas, detectable with a burning splint.

• The hydrogen gas is tested by a burning splint.

• Mg, Al, Zn, Fe do not react directly with cold water but react with steam.

• Some metals (e.g., lead, copper, mercury, silver, platinum, gold) do not react with water, or steam. This means they are less reactive and need stronger reactions to react with acids.

Reactions with acids:

• Dilute acids react with many metals, producing hydrogen gas.
• Metals + dilute acids → metal salt + hydrogen gas This reaction is used to test metals' reactivity, placing different metals into the same acid to discover their reactivity.

Displacement Reactions

• A more reactive metal can displace a less reactive metal from its compound in an aqueous solution.
• This is a displacement reaction.

Unit 11: Corrosion

• Corrosion is the reaction of metals with oxygen, water, or other substances in the environment.
• This is a common chemical reaction, damaging the structure and mechanical properties of metals.
• Metal corrosion loses its strength and shine.

Unit 11: Rusting

• Rusting is a specific type of corrosion that affects iron and steel.
• Iron rusts in the presence of both oxygen (O₂) and water (H₂O).
• A general equation for rusting involves the formation of hydrated iron(III) oxide (rust).

Extraction of Aluminium

• Cryolite is added to lower the melting point of aluminium oxide for easier extraction using electrolysis. This makes the compound more stable and harder to extract.

Chemical Weathering

• Carbon dioxide in the air dissolves in water to form carbonic acid, causing weathering in limestone.
• Limestone reacts with carbonic acid to form calcium hydrogencarbonate, which dissolves in water.
• Limestone is broken down over time by chemical weathering.

Detection of Ions

• Flame tests and precipitation reactions are used to identify specific metal ions in a solution, like chloride ions or water.

This quiz covers key concepts related to the occurrence and extraction of metals from ores. It discusses how different metals are found in nature, their reactions with oxygen, and methods used for extracting them. Test your understanding of metal properties and extraction processes.