[Chemistry Class Notes] Materials Pdf for Exam

What is Material?

Material is the matter, an object is made up of. It is a relatively broad term to be defined. They are classified based upon their properties. They have properties like hardness, strength, stiffness, thermal conductivity, heat capacity, permeability, and magnetism, etc. Materials are the basic matter used in industry to be processed and purified to give other materials or objects to be used. The science dealing with the study of material is called materials science. Materials have a wide range of use. So, they are also classified based upon their use in industries. The process of determining materials to be used for an application is called material selection. 

To Understand What is Meant By Material Properties

• In Chemistry, knowing the properties is very important for scientists if they aim to understand what is a material, how it reacts with the other common materials around us. 

• Materials have a wide range of properties. However, scientifically the physical and chemical properties of matter are considered. 

• Physical properties may further be classified into electric, magnetic, thermal, and mechanical properties. 

• Chemical properties of material include their states i.e. solid, liquid, gaseous, solubility, pH, reactivity, surface tension, surface energy, corrosion, etc. 

• Mechanical properties of materials include their elasticity, plasticity, ductility, durability, brittleness, hardness, malleability, resilience, stiffness, viscosity, etc. 

Some of the key properties of materials that are considered for a given application are given below.

• Elasticity: The material tends to return to its original size and shape when the force is removed. Plasticity is the phenomenon opposite to elasticity where the material holds the new shape.

• Conductivity: Thermal conductivity is the amount of heat flowing through a material. 

• Density: It is described by the mass of the material per cubic centimetre.  

• Ductility/malleability: The ability of a material to change shape when stretched without deforming is ductility or malleability. 

Materials and Their Classification Bases on Properties

Based on the various properties of materials can be classified into several categories.  Materials based upon atomic structure and chemical properties can be divided into metals, ceramics, and polymers. 

• Metals: This group of materials is composed of metallic elements like gold, iron, copper, nickel, and aluminium, etc. These materials are stiff, strong, and mostly elastic. Metals like gold and silver are ductile yet fracture resistant.

• Ceramics: This group of material has metallic and non-metallic compounds, mostly oxides, nitrides, and carbides. They are relatively stiff and strong but also brittle and susceptible to fracture.

• Polymers: They include plastic and rubber materials. Some common polymers are polyethylene, polyvinyl chloride, and nylon, etc. They are not as stiff or as strong as the metals or ceramics. They have low densities. They are very ductile i.e. easily made into different shapes. This is also a limitation of polymers since they are pliable they decompose or soften in a harsh environment or higher temperature.

• Composites: When the above two materials are composed together, the material is called a composite. Most of these are man-made, only a few are naturally occurring. An example of a composite is fibreglass which is stiff, strong, and ductile.

• Semiconductors: These materials have properties intermediate between the conductors and insulators. Some semiconducting crystals are Silicon and Germanium.  

What is Meant By Raw Material?

The material that is unprocessed or little processed and is used to make vast quantities of products is raw material. It is the basic form in which material is available naturally. These materials are further utilized by industries to produce finished products and goods. These materials are divided into direct and indirect materials. Direct materials are the raw materials used in the final product. Indirect materials are used in production but are not in the final product. Examples of raw materials are crude oil, iron ore, air, water, mineral, coal, cotton, raw biomass, etc. Metallic raw materials include tin, copper, bauxite, iron ore, lead, etc.