Untitled Quiz

Pure Substances

• Materials made up of the same kind of particles are known as pure substances
• A given element or compound is a pure substance because it is made up of atoms or molecules of the same kind
• Different elements or compounds differ in their physical and chemical properties since they are made up of different kinds of atoms or molecules

Classification of Elements

• There are approximately 118 elements known today
• Classifying all the properties of individual elements separately is difficult
• Elements with similar properties are grouped together to study their general characteristics
• Elements are broadly classified into metals and nonmetals, based on their physical and chemical properties

Occurrence of Elements

• Metals are abundant in the Earth's crust, with aluminum being the most abundant
• Metals like sodium, potassium, aluminum, and magnesium are often found in their compound forms (oxides, sulphides, carbonates)
• Many non-metals are found in their free state in the atmosphere (oxygen, nitrogen)
• Some non-metals can exist either in their pure form or as compounds (sulphur)
• Some non-metals exist in different forms in their native state (carbon - diamond, graphite, fullerene)

Minerals and Ores

• A mineral is a naturally occurring inorganic substance found underground
• An ore is a mineral from which one or more metals can be extracted profitably (ex: bauxite for aluminum, hematite for iron)
• Metallurgy is the process of extracting a metal in pure form from its ore, this process generally involves concentration and reduction of the ore, and refining of the metal

Physical Properties

• Physical State: Most metals are solid at room temperature, with mercury being the exception (liquid)
• Melting and Boiling Points: Metals typically have high melting and boiling points (exceptions exist); non-metals tend to have lower melting and boiling points (exceptions exist)
• Density: Most metals have relatively high densities, some exceptions exist in metals such as sodium and potassium
• Hardness: Most metals are hard, exceptions include sodium and potassium; non-metals are generally brittle and break easily
• Lustre: Metals shine (metallic luster); non-metals often have a dull appearance, iodine being an exception
• The properties of metals and non-metals differ

Malleability, Ductility, Tensile Strength, and Conductivity

• Malleability: Metals can be hammered into thin sheets without breaking; non-metals are brittle
• Ductility: Metals can be drawn into thin wires; non-metals are often not ductile
• Tensile Strength: Metals are generally strong; non-metals (with exceptions like carbon fiber) generally aren't as strong
• Conductivity: Metals are good conductors of heat and electricity; non-metals, with exceptions like graphite, are generally poor conductors

Chemical Properties

• Reaction with Oxygen: Metals typically react with oxygen to form metallic oxides, which are basic in nature. Non-metals react with oxygen to form non-metallic oxides that are, in most cases, acidic.
• Reaction with Water: Some reactive metals (e.g., sodium, potassium, magnesium) react vigorously with water, while others (e.g., copper, silver, gold) do not. Non-metals generally do not react with water.
• Reaction with Acids: Most metals react with dilute acids to liberate hydrogen gas and form metal salts (e.g., zinc with hydrochloric acid); some metals do not react with certain acids, or won't react with acids in their cold state
• Reaction with Alkalis: Some metals (e.g., aluminum, zinc) react with alkalis to form their salts and liberate hydrogen gas. Most metals do not react with alkalis

Reactivity of Metals

• Metals vary in their reactivity; reactivity series of metals can be used to identify the relative reactivity of different metals;
• More reactive metals are placed at the top of the series; less reactive metals are closer to the bottom

Displacement Reactions

• More reactive metals can displace less reactive metals from their compounds or solutions.
• This process is called displacement reaction

Noble Metals

• Noble metals (e.g., platinum, gold) are unreactive and do not react with most substances;
• They retain their lustre even when exposed to the environment
• They are malleable and ductile and are often used in jewelry

Uses of Metals, Alloys, and Non-metals

• Metals are used in many applications including cooking, electrical wiring; alloys, which are homogenous mixtures of two or more metals, are also employed in various applications
• Non-metals are essential to many industries and processes include industrial manufacturing of materials such as fertilizers, and for agricultural activities.