Chapter 1 - Materials in our world

1.1 Materials Science

Definitions

Material — substances that are used to make objects.

                    The way a material is used is determined by the material’s physical and                     chemical properties.

Elements — pure substances that are made up of just one type of atom

Compounds — pure substances made up of more than one type of atom

                        the formula indicates the relative number of atoms of each element (SiO2)

Metals

  • Properties; high tensile strength, ductilility, malleability, shiny lustre, high melting points and thermal + electrical conductivity

  • Alloy — mixture of a metal with other metals or small amounts of non-metals

Polymers

  • Polymer — material with a molecular structure that is composed of many repeating smaller units bonded together.

  • Physical properties; less dense and corrosion resistant, good electrical resistance, good compatibility with human tissue.


Ceramics

  • Ceramic — inorganic non-metallic solid. Contain metal, non-metal and metalloid elements help together by ionic and covalent bonds.

  • Degree of order ranges from highly ordered (crystalline) → highly irregular (anamorphous)

  • Properties; hard, high compressive strength, withstand high temperatures, good insulators. Sometimes semiconductor and superconducting properties.


Composites

  • Composite — combination of two or more distinct materials with significantly different physical and chemical properties.

  • Properties; individualised. Can demonstrate a range of properties that would be unobtainable by one individual material.

1.2 Nanotechnology

Nanotechnology — branch of materials science that investigates the design, properties and applications of materials produced at a scale of 1 to 100 nanometers.

Nanoscale

  • Nanoscale — refers to structures that are between 1 and 100 nanometers

  • Nanometer (nm) — is one billionth of a meter (10-9m)

Nanomaterials

  • Nanomaterials — substances, natural and synthetic, that are composed of single units that exist in the nanoscale.

  • Fullerenes — 3D structures formed by networks of carbon atoms

Top Down Fabrication

  • Material of a larger scale than desired → material is then selectively removed or progressively reduced - until requires size and shape is achieved

  • Advantages; large quantities can be produced cheaply, demonstrates good level of uniformity

  • Disadvantages; limited to simple structures, limited by the scale of tools used to remove material from the starting medium.

Bottom Up Fabrication

  • Definition; Physically building/growing tge required material atom by atom or molecule by molecule

  • In early stages of development

  • Advantages; can be used for far more complicated structures

  • Disadvantages; do not scale up to commercial level efficiency

Nanoparticles

  • Definition; Spherical particles with diameters of 1-100 nm.

  • As materials are reduced to the nanoscale (), they lose the consistent, familiar properties of their bulk form and adopt entirely new, size-dependent behaviours.

  • Problem; are so small that they can travel through air, skin and into your bloodstream. Inside the body, the particles can interact with biomolecules to cause unwanted chemical reactions. Therefore, nanoparticles can be dangerous when inhaled or make contact with skin. Eg, sunscreen, fabrics, cosmetics

1.3 Purifying Materials

Separation By Particle Size

Seiving

  • Seperate a mixture of solids with different particle sizes

  • Involves; passing mixture through a mess, particles smaller than the wholes pass through, leaving the larger behind.

  • Eg → Used during baking to seperate lumps from powders such as flour or cocoa.

Filtration

  • Seperate solid particles from a liquid or gas.

  • Eg → air filters in vacuum cleaners, pool filters, tea bags

Gravitational filtration

  • Uses weight of the solid-liquid mixture to push the mixture through filter paper

Vacuum filtrations

  • Faster than gravitational

  • Helps dry residue quicker

  • a rapid laboratory technique used to separate solid particles from a liquid using reduced pressure (suction)

Separation By Density

  • Density; measure of the mass per unit of volume of a substance

  • Denser substance will sink, less dense will float

Sedimentation and Decantation

Sedimentation; is the passive settling of heavier particles to the bottom

Decantation; is the active pouring off of the top liquid layer

Separation funnels

  • Can be used if two liquids have different densities and are immiscible (don’t mix), then the liquids can be separated with a funnel.

  • Two layers will form, less dense floats, denser sinks to bottom

  • Is a liquid-liquid extraction

Centrifugation

  • Spinning a mixture rapidly can speed up the sedimentation process and extract finer particles.

  • Spinning the mixture results in the denser particles being pushed to the outside of the container by centrifugal force.

Separation By Boiling Point

Evaporation

  • Some solids dissolve in liquids to form a solution. Liquid = solvent. Dissolved solid = solute

  • Dissolved solids cannot be seperated using filtration, sedimentation or centrifugation.

  • Needs to be evaporated/boiled off

  • Definition; the process where liquid water absorbs energy (heat) and transforms into gaseous water vapour, allowing it to rise from the Earth's surface into the atmosphere

Distillation

  • Same principle as evporation, but is performed in an apparatus

  • Solution is heated in a flask known as the distillation flask to vaporise the liquid

Fractional Distillation

  • Seperate miscible (can mix) liquids

  • Same apparatus as simple distillation… but has a fractionating column placed in between the flask containing the mixture and condenser

  • Column allows increased contact beween rising vapour and falling condensate

Separation By Electric Charge

Electrostatic Separation

  • Objects that have opposite charges attract each other

  • Force of attraction between opposite charges = electrostatic force

  • Used to separate charged from uncharged particles

  • Seperate solid particles from gas using electrostatic filters

Chromatography

  • Layer Chromatography (TLC), Gas Chromatography (GC), Paper Chromatography and High Performance Liquid Chromatography (HPLC)

  • Chromatography; seperates liquids or gases based on their differing affinity for various materials present in th Chromatography apparatus

  • High affinity - mobile phase + Low affinity - stationary phase = moved quickly through system as mobile phase moves

  • Low affinity - mobile phase + High affinity - stationary phase = remain in system fro longer, effecting separation of the compounds